NASA Astronauts Return to Earth, Land Safely in Kazakhstan

Three members of the Expedition 54 crew aboard the International Space Station (ISS), including NASA astronauts Mark Vande Hei and Joe Acaba, returned to Earth on Tuesday after months of performing research and spacewalks in low-Earth orbit.

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CloudSat Exits the 'A-Train'

MISSION STATUS REPORT

Mission managers at NASA's Jet Propulsion Laboratory in Pasadena, California, this week lowered the orbit of the nearly 12-year-old CloudSat satellite following the loss of one of its reaction wheels, which control its orientation in orbit. While CloudSat's science mission will continue, it will no longer fly as part of the Afternoon Constellation, or A-Train -- six Earth-monitoring satellites that fly in a coordinated orbit to advance our understanding of how Earth functions as a system.

CloudSat launched in 2006 to improve understanding of the role clouds play in our climate system. It joined the A-Train about a month later. In April 2011, the spacecraft experienced a technical issue affecting the ability of the battery to provide enough current to power all spacecraft systems during the time in each orbit when the spacecraft is on the dark side of the planet and the spacecraft's solar panels are not illuminated. In response, spacecraft engineers at Ball Aerospace in Boulder, Colorado, developed a new operational mode for CloudSat that enabled it to continue science operations, but only during the part of each orbit when the spacecraft is in sunlight.

Recognizing the vulnerable nature of the spacecraft battery and the age of other spacecraft systems, the CloudSat project developed a set of criteria under which they would exit the A-Train. One criterion was the loss of one of CloudSat's four reaction wheels. Although CloudSat can conduct science operations using only three reaction wheels, a subsequent loss of a second reaction wheel could leave the spacecraft unable to maneuver or change its orientation. Without the capability to maneuver, the satellite could drift too close to another A-Train satellite.

In June 2017, one of CloudSat's reaction wheels displayed significant friction. It was subsequently determined that the wheel would no longer be usable, thus triggering preparations to exit the A-Train.

On Feb. 22, CloudSat successfully executed two thruster burns, placing the satellite in an orbit below the altitude of the A-Train. After telemetry has been analyzed, mission managers will determine if a third orbit trim burn is necessary. CloudSat will remain in this "safe-exit orbit" while the project studies orbit options for continuing science operations even farther below the A-Train.

CloudSat is the first satellite to use an advanced cloud-profiling radar to "slice" through clouds to see their vertical structure, providing a completely new observational capability from space. The mission furnishes data that evaluate and improve the way clouds and precipitation are represented in global models, contributing to better predictions of clouds and their role in climate change.

Among the mission's many science accomplishments to date, CloudSat has provided the capability to look jointly at clouds and at the precipitation that comes from them, spotlighting flaws in climate model physics: models produce precipitation too frequently, and the modeled precipitation is lighter than actual observations. CloudSat directly quantified, for the first time, global snowfall and found that climate models overestimate Antarctic snowfall, many by more than 100 percent.

The A-Train satellites rush along together like a train on a "track" 705 miles (438 kilometers) above Earth's surface, flying minutes, and sometimes seconds, behind one another. Together, the satellites and their more than 15 scientific instruments work as a united, powerful tool to examine many different aspects of our home planet. The A-Train has proven to be a successful integrated approach to observing Earth because it allows multiple instruments to observe the same location on Earth nearly simultaneously as they pass overhead. In addition to CloudSat (a partnership with the Canadian Space Agency and the U.S. Air Force), the other satellites currently in the A-Train include NASA's Aqua, Orbiting Carbon Observatory-2 and Aura spacecraft; the NASA/Centre National d'études Spatiales (CNES) Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) spacecraft; and the Japan Aerospace Exploration Agency's Global Change Observation Mission - Water (GCOM-W1) satellite.

With CloudSat now in an orbit below the A-Train, it will occasionally pass beneath the constellation, enabling the mission to collect data in support of some of its pre-A-Train-exit data products.

For information on CloudSat and the A-Train, visit:

http://www.nasa.gov/CloudSat

http://CloudSat.atmos.colostate.edu

https://atrain.nasa.gov

News Media Contact

Alan Buis

Jet Propulsion Laboratory, Pasadena, California

818-354-0474

Alan.buis@jpl.nasa.gov

2018-038

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NASA Astronauts Available for Final Interviews Before Space Station Mission

Veteran NASA astronauts Ricky Arnold and Drew Feustel will be available Thursday, March 1, for final interviews before their launch to the International Space Station. The interviews will air live on NASA Television and the agency’s website.

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Seven Ways Mars InSight is Different

NASA's Mars InSight lander team is preparing to ship the spacecraft from Lockheed Martin Space in Denver, where it was built and tested, to Vandenberg Air Force Base in California, where it will become the first interplanetary mission to launch from the West Coast. The project is led by NASA's Jet Propulsion Laboratory in Pasadena, California.

We know what "The Red Planet" looks like from the outside -- but what's going on under the surface of Mars? Find out more in the 60-second video from NASA's Jet Propulsion Laboratory.

NASA has a long and successful track record at Mars. Since 1965, it has flown by, orbited, landed and roved across the surface of the Red Planet. What can InSight -- planned for launch in May -- do that hasn't been done before?

1. InSight is the first mission to study the deep interior of Mars.

A dictionary definition of "insight" is to see the inner nature of something. InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) will do just that. InSight will take the "vital signs" of Mars: its pulse (seismology), temperature (heat flow), and its reflexes (radio science). It will be the first thorough check-up since the planet formed 4.5 billion years ago.

2. InSight will teach us about planets like our own.

InSight's team hopes that by studying the deep interior of Mars, we can learn how other rocky planets form. Earth and Mars were molded from the same primordial stuff more than 4 billion years ago, but then became quite different. Why didn't they share the same fate?

When it comes to rocky planets, we've only studied one in great detail: Earth. By comparing Earth's interior to that of Mars, InSight's team hopes to better understand our solar system. What they learn might even aid the search for Earth-like exoplanets, narrowing down which ones might be able to support life. So while InSight is a Mars mission, it's also more than a Mars mission.

3. InSight will try to detect marsquakes for the first time.

One key way InSight will peer into the Martian interior is by studying motion underground -- what we know as marsquakes. NASA has not attempted to do this kind of science since the Viking mission. Both Viking landers had their seismometers on top of the spacecraft, where they produced noisy data. InSight's seismometer will be placed directly on the Martian surface, which will provide much cleaner data.

Scientists have seen a lot of evidence suggesting Mars has quakes. But unlike quakes on Earth, which are mostly caused by tectonic plates moving around, marsquakes would be caused by other types of tectonic activity, such as volcanism and cracks forming in the planet's crust. In addition, meteor impacts can create seismic waves, which InSight will try to detect.

Each marsquake would be like a flashbulb that illuminates the structure of the planet's interior. By studying how seismic waves pass through the different layers of the planet (the crust, mantle and core), scientists can deduce the depths of these layers and what they're made of. In this way, seismology is like taking an X-ray of the interior of Mars.

Scientists think it's likely they'll see between a dozen and a hundred marsquakes over the course of two Earth years. The quakes are likely to be no bigger than a 6.0 on the Richter scale, which would be plenty of energy for revealing secrets about the planet's interior.

4. First interplanetary launch from the West Coast

All of NASA's interplanetary launches to date have been from Florida, in part because the physics of launching off the East Coast are better for journeys to other planets. But InSight will break the mold by launching from Vandenberg Air Force Base in California. It will be the first launch to another planet from the West Coast.

InSight will ride on top of a powerful Atlas V 401 rocket, which allows for a planetary trajectory to Mars from either coast. Vandenberg was ultimately chosen because it had more availability during InSight's launch period.

A whole new region will get to see an interplanetary launch when InSight rockets into the sky. In a clear, pre-dawn sky, the launch may be visible in California from Santa Maria to San Diego.

5. First interplanetary CubeSat

The rocket that will loft InSight beyond Earth will also launch a separate NASA technology experiment: two mini-spacecraft called Mars Cube One, or MarCO. These briefcase-sized CubeSats will fly on their own path to Mars behind InSight.

Their objective is to relay back InSight data as it enters the Martian atmosphere and lands. It will be a first test of miniaturized CubeSat technology at another planet, which researchers hope can offer new capabilities to future missions.

If successful, the MarCOs could represent a new kind of data relay to Earth. InSight's success is independent of its CubeSat tag-alongs.

6. InSight could teach us how Martian volcanoes were formed.

Mars is home to some impressive volcanic features. That includes Tharsis -- a plateau with some of the biggest volcanoes in the solar system. Heat escaping from deep within the planet drives the formation of these types of features, as well as many others on rocky planets. InSight includes a self-hammering heat probe that will burrow down to 16 feet (5 meters) into the Martian soil to measure the heat flow from the planet's interior for the first time. Combining the rate of heat flow with other InSight data will reveal how energy within the planet drives changes on the surface.

7. Mars is a time machine

Studying Mars lets us travel to the ancient past. While Earth and Venus have tectonic systems that have destroyed most of the evidence of their early history, much of the Red Planet has remained static for more than 3 billion years. Because Mars is just one-third the size of Earth and Venus, it contains less energy to power the processes that change a planet's structure. That makes it a fossil planet in many ways, with the secrets of our solar system's early history locked deep inside.

Learn more about InSight's mission goals and instrumentation at a live public talk, part of JPL's von Karman lecture series, on Thursday, Feb. 22 at 7 p.m. PST (10 p.m. EST). The event will be streamed live onhttp://YouTube.com/NASAJPL/live .

More information about InSight is at:

https://mars.nasa.gov/insight

News Media Contact

Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433

andrew.c.good@jpl.nasa.gov

2018-037

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International Space Station Crew Landing to Air Live on NASA Television

Three residents of the International Space Station are scheduled to complete their mission on the complex on Tuesday, Feb. 27. Coverage of their departure and landing back on Earth will air on NASA Television and the agency’s website.

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Students in California to Speak with NASA Astronaut on Space Station

Students at Para Los Niños in Los Angeles will speak with a NASA astronaut living, working and doing research aboard the International Space Station at 12:55 p.m. EST Thursday, Feb. 22. The 20-minute, Earth-to-space call will air live on NASA Television and the agency’s website.

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NASA Awards Contract for Facilities Operations, Maintenance Services

NASA has awarded the Facilities Operations and Maintenance Services (FOMS) III contract, an 8(a) set-aside acquisition, to Akima Support Operations, LLC of Colorado Springs, Colorado.

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Nearly a Decade After Mars Phoenix Landed, Another Look

A recent view from Mars orbit of the site where NASA's Phoenix Mars mission landed on far-northern Mars nearly a decade ago shows that dust has covered some marks of the landing.

The Phoenix lander itself, plus its back shell and parachute, are still visible in the image taken Dec. 21, 2017, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. But an animated-blink comparison with an image from about two months after the May 25, 2008, landing shows that patches of ground that had been darkened by removal of dust during landing events have become coated with dust again.

In August 2008, Phoenix completed its three-month mission studying Martian ice, soil and atmosphere. The lander worked for two additional months before reduced sunlight caused energy to become insufficient to keep the lander functioning. The solar-powered robot was not designed to survive through the dark and cold conditions of a Martian arctic winter.

For additional information about the Phoenix mission, visit:

https://www.nasa.gov/mission_pages/phoenix/main/index.html

For additional information about the Mars Reconnaissance Orbiter mission, visit:

https://mars.nasa.gov/mro/

News Media Contact

Andrew Good / Guy Webster

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433 / 818-354-6278

andrew.c.good@jpl.nasa.gov / guy.webster@jpl.nasa.gov

2018-036

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New Study Brings Antarctic Ice Loss Into Sharper Focus

MARS RECONNAISSANCE ORBITER MISSION STATUS REPORT

NASA's Mars Reconnaissance Orbiter (MRO), at Mars since 2006, put itself into a precautionary standby mode on Feb. 15 in response to sensing an unexpectedly low battery voltage.

The orbiter is solar-powered but relies on a pair of nickel-hydrogen batteries during periods when it is in the shadow of Mars for a portion of each orbit. The two are used together, maintaining almost identical charge during normal operations.

The spacecraft remains in communication with Earth and has been maintaining safe, stable temperatures and power, but has suspended its science observations and its service as a communications relay for Mars rovers. Normal voltage has been restored, and the spacecraft is being monitored continuously until the troubleshooting is complete.

"We're in the diagnostic stage, to better understand the behavior of the batteries and ways to give ourselves more options for managing them in the future," said MRO Project Manager Dan Johnston of NASA's Jet Propulsion Laboratory, Pasadena, California. "We will restore MRO's service as a relay for other missions as soon as we can do so with confidence in spacecraft safety -- likely in about one week. After that, we will resume science observations."

NASA's Mars Reconnaissance Orbiter entered orbit around the Red Planet on March 10, 2006. Since then, it has returned more data than all other past and current interplanetary missions combined, with a tally of more than 317 terabits so far.

The mission met all its science goals in a two-year primary science phase. Five extensions, the latest beginning in 2016, have added to the science returns. The longevity of the mission has given researchers tools to study seasonal and longer-term changes on Mars. Among other current activities, the orbiter is examining possible landing sites for future missions to Mars and relaying communications to Earth from NASA's two active Mars rovers.

JPL, a division of Caltech in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space, Denver, built the orbiter and collaborates with JPL to operate it. For more information about the Mars Reconnaissance Orbiter, visit:

https://www.nasa.gov/mro

https://mars.jpl.nasa.gov/mro/

News Media Contact

Andrew Good / Guy Webster

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433 / 818-354-6278

andrew.c.good@jpl.nasa.gov / guy.webster@jpl.nasa.gov

2018-034

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Mars Orbiter on Precautionary Standby Status

MARS RECONNAISSANCE ORBITER MISSION STATUS REPORT

NASA's Mars Reconnaissance Orbiter (MRO), at Mars since 2006, put itself into a precautionary standby mode on Feb. 15 in response to sensing an unexpectedly low battery voltage.

The orbiter is solar-powered but relies on a pair of nickel-hydrogen batteries during periods when it is in the shadow of Mars for a portion of each orbit. The two are used together, maintaining almost identical charge during normal operations.

The spacecraft remains in communication with Earth and has been maintaining safe, stable temperatures and power, but has suspended its science observations and its service as a communications relay for Mars rovers. Normal voltage has been restored, and the spacecraft is being monitored continuously until the troubleshooting is complete.

"We're in the diagnostic stage, to better understand the behavior of the batteries and ways to give ourselves more options for managing them in the future," said MRO Project Manager Dan Johnston of NASA's Jet Propulsion Laboratory, Pasadena, California. "We will restore MRO's service as a relay for other missions as soon as we can do so with confidence in spacecraft safety -- likely in about one week. After that, we will resume science observations."

NASA's Mars Reconnaissance Orbiter entered orbit around the Red Planet on March 10, 2006. Since then, it has returned more data than all other past and current interplanetary missions combined, with a tally of more than 317 terabits so far.

The mission met all its science goals in a two-year primary science phase. Five extensions, the latest beginning in 2016, have added to the science returns. The longevity of the mission has given researchers tools to study seasonal and longer-term changes on Mars. Among other current activities, the orbiter is examining possible landing sites for future missions to Mars and relaying communications to Earth from NASA's two active Mars rovers.

JPL, a division of Caltech in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space, Denver, built the orbiter and collaborates with JPL to operate it. For more information about the Mars Reconnaissance Orbiter, visit:

https://www.nasa.gov/mro

https://mars.jpl.nasa.gov/mro/

News Media Contact

Andrew Good / Guy Webster

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433 / 818-354-6278

andrew.c.good@jpl.nasa.gov / guy.webster@jpl.nasa.gov

2018-034

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5,000 Days on Mars; Solar-Powered Rover Approaching 5,000th Martian Dawn

The Sun will rise on NASA's solar-powered Mars rover Opportunity for the 5,000th time on Saturday, sending rays of energy to a golf-cart-size robotic field geologist that continues to provide revelations about the Red Planet.

"Five thousand sols after the start of our 90-sol mission, this amazing rover is still showing us surprises on Mars," said Opportunity Project Manager John Callas, of NASA's Jet Propulsion Laboratory, Pasadena, California.

A Martian "sol" lasts about 40 minutes longer than an Earth day, and a Martian year lasts nearly two Earth years. Opportunity's Sol 1 was landing day, Jan. 25, 2004 (that's in Universal Time; it was Jan. 24 in California). The prime mission was planned to last 90 sols. NASA did not expect the rover to survive through a Martian winter. Sol 5,000 will begin early Friday, Universal Time, with the 4,999th dawn a few hours later. Opportunity has worked actively right through the lowest-energy months of its eighth Martian winter.

From the rover's perspective on the inside slope of the western rim of Endeavour Crater, the milestone sunrise will appear over the basin's eastern rim, about 14 miles (22 kilometers) away. Opportunity has driven over 28 miles (45 kilometers) from its landing site to its current location about one-third of the way down "Perseverance Valley," a shallow channel incised from the rim's crest of the crater's floor. The rover has returned about 225,000 images, all promptly made public online.

"We've reached lots of milestones, and this is one more," Callas said, "but more important than the numbers are the exploration and the scientific discoveries."

The mission made headlines during its first months with the evidence about groundwater and surface water environments on ancient Mars. Opportunity trekked to increasingly larger craters to look deeper into Mars and father back into Martian history, reaching Endeavour Crater in 2011. Researchers are now using the rover to investigate the processes that shaped Perseverance Valley.

For more about Opportunity's adventures and discoveries, see:

https://www.nasa.gov/rovers

https://marsrovers.jpl.nasa.gov

News Media Contact

Guy Webster / Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-6278 / 818-393-2433

guy.webster@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

Laurie Cantillo / Dwayne Brown

NASA Headquarters, Washington

202-358-1077 / 202-358-1726

laura.l.cantillo@nasa.gov / dwayne.c.brown@nasa.gov

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Long-Lived Mars Rover Opportunity Keeps Finding Surprises

NASA's Mars Exploration Rover Opportunity keeps providing surprises about the Red Planet, most recently with observations of possible "rock stripes."

The ground texture seen in recent images from the rover resembles a smudged version of very distinctive stone stripes on some mountain slopes on Earth that result from repeated cycles of freezing and thawing of wet soil. But it might also be due to wind, downhill transport, other processes or a combination.

Opportunity landed on Mars in January 2004. As it reaches the 5,000th Martian day, or sol, of what was planned as a 90-sol mission, it is investigating a channel called "Perseverance Valley," which descends the inboard slope of the western rim of Endeavour Crater.

"Perseverance Valley is a special place, like having a new mission again after all these years," said Opportunity Deputy Principal Investigator Ray Arvidson of Washington University in St. Louis. "We already knew it was unlike any place any Mars rover has seen before, even if we don't yet know how it formed, and now we're seeing surfaces that look like stone stripes. It's mysterious. It's exciting. I think the set of observations we'll get will enable us to understand it."

On some slopes within the valley, the soil and gravel particles appear to have become organized into narrow rows or corrugations, parallel to the slope, alternating between rows with more gravel and rows with less.

The origin of the whole valley is uncertain. Rover-team scientists are analyzing various clues that suggest actions of water, wind or ice. They are also considering a range of possible explanations for the stripes, and remain uncertain about whether this texture results from processes of relatively modern Mars or a much older Mars.

Other lines of evidence have convinced Mars experts that, on a scale of hundreds of thousands of years, Mars goes through cycles when the tilt or obliquity of its axis increases so much that some of the water now frozen at the poles vaporizes into the atmosphere and then becomes snow or frost accumulating nearer the equator.

"One possible explanation of these stripes is that they are relics from a time of greater obliquity when snow packs on the rim seasonally melted enough to moisten the soil, and then freeze-thaw cycles organized the small rocks into stripes," Arvidson said. "Gravitational downhill movement may be diffusing them so they don't look as crisp as when they were fresh."

Bernard Hallet of the University of Washington, Seattle, agrees the alignments seen in images of Perseverance Valley are not as distinctive as the stone stripes he has studied on Earth. Field measurements on Earth, near the summit of Hawaii's Mauna Kea where the soil freezes every night but is often dry, have documented how those form when temperature and ground conditions are right: Soils with a mix of silt, sand and gravel expand more where the finer-grain material is most prevalent and retains more water. Freezing expands the soil, pushing larger particles up. If they move to the side, as well as down the general slope, due to gravity or wind, they tend to move away from the finer-grain concentrations and stretch out downslope. Where larger particles become more concentrated, the ground expands less. The process repeats hundreds or thousands of times, and the pattern self-organizes into alternating stripes.

Perseverance Valley holds rocks carved by sand blowing uphill from the crater floor, and wind might also be the key in sorting larger particles into rows parallel to the slope.

"Debris from relatively fresh impact craters is scattered over the surface of the area, complicating assessment of effects of wind," said Opportunity science-team member Robert Sullivan of Cornell University, Ithaca, New York. "I don't know what these stripes are, and I don't think anyone else knows for sure what they are, so we're entertaining multiple hypotheses and gathering more data to figure it out."

Every sol Opportunity keeps working may add information to help solve some puzzles and find new ones. For more information about Opportunity, visit:

https://www.nasa.gov/rovers

https://marsrovers.jpl.nasa.gov

News Media Contact

Guy Webster / Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-6278 / 818-393-2433

guy.webster@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

Laurie Cantillo / Dwayne Brown

NASA Headquarters, Washington

202-358-1077 / 202-358-1726

laura.l.cantillo@nasa.gov / dwayne.c.brown@nasa.gov

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NASA Television Coverage Set for Weather Satellite Science Briefing, Launch

The National Oceanic and Atmospheric Administration’s (NOAA’s) newest weather satellite, Geostationary Operational Environmental Satellite-S (GOES-S), is scheduled to launch Thursday, March 1. The launch, as well as prelaunch and science briefings on Tuesday, Feb. 27, will air live on NASA Television and the agency’s website.

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NASA to Host National Space Council Meeting at Kennedy Space Center

NASA’s Kennedy Space Center in Florida will host a meeting of the National Space Council, chaired by Vice President Mike Pence on Wednesday, Feb. 21. NASA Television and the agency’s website will provide live coverage of the meeting beginning at 10 a.m. EST.

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NASA Awards Contract for Construction, Maintenance, Environmental, Testing Services

NASA has selected Firelake-Arrowhead NASA Services of Lenexa, Kansas, to perform facility management, surveying, energy management, life safety code compliance and environmental management services for the agency’s Glenn Research Center in Cleveland.

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New Mexico Students to Speak with NASA Astronaut on Space Station

Students from six schools in Alamogordo, New Mexico, will speak with a NASA astronaut living, working and doing research aboard the International Space Station at 11 a.m. EST Wednesday, Feb. 21.

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Minnesota Students to Speak with NASA Astronauts on Space Station

Students in central Minnesota will speak with NASA astronauts living, working and doing research aboard the International Space Station at 1:35 p.m. EST Tuesday, Feb. 20.

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NASA Invites Media to Upcoming Space Station Cargo Launch

Media accreditation now is open for the launch of the next SpaceX delivery of supplies and equipment, including science investigations, to the International Space Station, currently targeted for no earlier than April.

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NASA TV to Air US Spacewalk at the International Space Station

Two astronauts will venture outside the International Space Station on Friday, Feb. 16, to move components for the station’s robotic system into long-term storage. Live coverage of the spacewalk will begin at 5:30 a.m. EST on NASA Television and the agency’s website.

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A Piece of Mars is Going Home

A chunk of Mars will soon be returning home.

A piece of a meteorite called Sayh al Uhaymir 008 (SaU008) will be carried on board NASA's Mars 2020 rover mission, now being built at the agency's Jet Propulsion Laboratory in Pasadena, California. This chunk will serve as target practice for a high-precision laser on the rover's arm.

Mars 2020's goal is ambitious: collect samples from the Red Planet's surface that a future mission could potentially return to Earth. One of the rover's many tools will be a laser designed to illuminate rock features as fine as a human hair.

That level of precision requires a calibration target to help tweak the laser's settings. Previous NASA rovers have included calibration targets as well. Depending on the instrument, the target material can include things like rock, metal or glass, and can often look like a painter's palette.

But working on this particular instrument sparked an idea among JPL scientists: why not use an actual piece of Mars? Earth has a limited supply of Martian meteorites, which scientists determined were blasted off Mars' surface millions of years ago.

These meteorites aren't as unique as the geologically diverse samples 2020 will collect. But they're still scientifically interesting -- and perfect for target practice.

"We're studying things on such a fine scale that slight misalignments, caused by changes in temperature or even the rover settling into sand, can require us to correct our aim," said Luther Beegle of JPL. Beegle is principal investigator for a laser instrument called SHERLOC (Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals). "By studying how the instrument sees a fixed target, we can understand how it will see a piece of the Martian surface."

SHERLOC will be the first instrument on Mars to use Raman and fluorescence spectroscopies, scientific techniques familiar to forensics experts. Whenever an ultraviolet light shines over certain carbon-based chemicals, they give off the same characteristic glow that you see under a black light.

Scientists can use this glow to detect chemicals that form in the presence of life. SHERLOC will photograph the rocks it studies, then map the chemicals it detects across those images. That adds a spatial context to the layers of data Mars 2020 will collect.

"This kind of science requires texture and organic chemicals -- two things that our target meteorite will provide," said Rohit Bhartia of JPL, SHERLOC's deputy principal investigator.

No Flaky Meteorites

Martian meteorites are precious in their rarity. Only about 200 have been confirmed by The Meteoritical Society, which has a database listing these vetted meteorites.

To select the right one for SHERLOC, JPL turned to contacts at NASA's Johnson Space Center in Houston, as well as the Natural History Museum of London. Not just any Martian meteorite would do: its condition would need to be solid enough that it would not flake apart during the intensity of launch and landing.

It also needed to possess certain chemical features to test SHERLOC's sensitivity. These had to be reasonably easy to detect repeatedly for the calibration target to be useful.

Experts tried several samples, cutting off thin bits to test whether they would crumble. Using a "flaky" sample could damage the entire meteorite in the process.

The SHERLOC team ultimately agreed on using SaU008, a meteorite found in Oman in 1999. Besides being more rugged than other samples, a piece of it was available courtesy of Caroline Smith, principal curator of meteorites at London's Natural History Museum.

"Every year, we provide hundreds of meteorite specimens to scientists all over the world for study," Smith said. "This is a first for us: sending one of our samples back home for the benefit of science."

SaU008 will be the first Martian meteorite to have a fragment return to the planet's surface -- though not the first on a return trip to Mars.

NASA's Mars Global Surveyor included a chunk of a meteorite known as Zagami. It's still floating around the Red Planet onboard the now-defunct orbiter.

Additionally, the team behind Mars2020's SuperCam instrument will be adding a Martian meteorite to their own calibration target.

Preparing for Humans on Mars

Along with its own Martian meteorite, SHERLOC's calibration target will include several interesting scientific samples for human spaceflight. These include materials that could be used to make spacesuit fabric, gloves and a helmet's visor.

By watching how they hold up under Martian weather, including radiation, NASA will be able to test these materials for future Mars missions.

"The SHERLOC instrument is a valuable opportunity to prepare for human spaceflight as well as to perform fundamental scientific investigations of the Martian surface," said Marc Fries, a SHERLOC co-investigator and curator of extraterrestrial materials at Johnson Space Center. "It gives us a convenient way to test material that will keep future astronauts safe when they get to Mars."

News Media Contact

Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433

andrew.c.good@jpl.nasa.gov

2018-030

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Farewell to a Pioneering Pollution Sensor

On Jan. 31, NASA ended the Tropospheric Emission Spectrometer's (TES) almost 14-year career of discovery. Launched in 2004 on NASA's Aura spacecraft, TES was the first instrument designed to monitor ozone in the lowest layers of the atmosphere directly from space. Its high-resolution observations led to new measurements of atmospheric gases that have altered our understanding of the Earth system.

TES was planned for a five-year mission but far outlasted that term. A mechanical arm on the instrument began stalling intermittently in 2010, affecting TES's ability to collect data continuously. The TES operations team adapted by operating the instrument to maximize science operations over time, attempting to extend the data set as long as possible. However, the stalling increased to the point that TES lost operations about half of last year. The data gaps hampered the use of TES data for research, leading to NASA's decision to decommission the instrument. It will remain on the Aura satellite, receiving enough power to keep it from getting so cold it might break and affect the two remaining functioning instruments.

"The fact that the instrument lasted as long as it did is a testament to the tenacity of the instrument teams responsible for designing, building and operating the instrument," said Kevin Bowman of NASA's Jet Propulsion Laboratory in Pasadena, California, the TES principal investigator.

A True Earth System Sounder

TES was originally conceived to measure ozone in the troposphere, the layer of atmosphere between the surface and the altitude where intercontinental jets fly, using high-spectral-resolution observations of thermal infrared radiation. However, TES cast a wider net, capturing signatures of a broad array of other atmospheric gases as well as ozone. That flexibility allowed the instrument to contribute to a wide range of studies -- not only atmospheric chemistry and the impacts of climate change, but studies of the cycles of water, nitrogen and carbon.

One of the surprises of the mission was the measurement of heavy water: water molecules composed of deuterium, an isotope of hydrogen that has more neutrons than normal hydrogen. The ratio of deuterium to "normal" water in water vapor gives clues to the vapor's history -- how it evaporated and fell as precipitation in the past -- which in turns helps scientists discern what controls the amount in the atmosphere.

Heavy water data have led to fundamental advances in our understanding of the water cycle that were not possible before, such as how tropical thunderstorms keep the troposphere hydrated, how much water in the atmosphere is evaporated from plants and soil as compared to surface water, and how water "exhaled" from southern Amazon vegetation jump-starts the rainforest's rainy season. JPL scientist John Worden, the pioneer of this measurement, said, "It's become one of the most important applications of TES. It gives us a unique window into Earth's hydrological cycle."

While the nitrogen cycle isn't as well measured or understood as the water cycle, nitrogen makes up 78 percent of the atmosphere, and its conversion to other chemical compounds is essential to life. TES demonstrated the first space measurement of a key nitrogen compound, ammonia. This compound is a widely used fertilizer for agriculture in solid form, but as a gas, it reacts with other compounds in the atmosphere to form harmful pollutants.

Another nitrogen compound, peroxyacetyl nitrate (PAN), can be lofted into the troposphere from fires and human emissions. Largely invisible in data collected at ground level, this pollutant can travel great distances before it settles back to the surface, where it can form ozone. TES showed how PAN varied globally, including how fires influenced its distribution. "TES really paved the way in our global understanding of both PAN and [ammonia], two keystone species in the atmospheric nitrogen cycle," said Emily Fischer, an assistant professor in the department of atmospheric science at Colorado State University, Fort Collins.

The Three Faces of Ozone

Ozone, a gas with both natural and human sources, is known for its multiple "personalities." In the stratosphere ozone is benign, protecting Earth from incoming ultraviolet radiation. In the troposphere, it has two distinct harmful functions, depending on altitude. At ground level it's a pollutant that hurts living plants and animals, including humans. Higher in the troposphere, it's the third most important human-produced greenhouse gas, trapping outgoing thermal radiation and warming the atmosphere.

TES data, in conjunction with data from other instruments on Aura, were used to disentangle these personalities, leading to a significantly better understanding of ozone and its impact on human health, climate and other parts of the Earth system.

Air currents in the mid- to upper troposphere carry ozone not only across continents but across oceans to other continents. A 2015 study using TES measurements found that the U.S. West Coast's tropospheric ozone levels were higher than expected, given decreased U.S. emissions, partly because of ozone that blew in across the Pacific Ocean from China. The rapid growth in Asian emissions of precursor gases -- gases that interact to create ozone, including carbon monoxide and nitrogen dioxide -- changed the global landscape of ozone.

"TES has borne witness to dramatic changes in which the gases that create ozone are produced. TES's remarkably stable measurements and ability to resolve the layers of the troposphere allowed us to separate natural changes from those driven by human activities," said JPL scientist Jessica Neu, a coauthor of the study.

Regional changes in emissions of ozone precursor gases alter not only the amount of ozone in the troposphere, but its efficiency as a greenhouse gas. Scientists used TES measurements of ozone's greenhouse effect, combined with chemical weather models, to quantify how the global patterns of these emissions have altered climate. "In order to both improve air quality and mitigate climate change, we need to understand how human pollutant emissions affect climate at the scales in which policies are enacted [that is, at the scale of a city, state or country]. TES data paved the way for how satellites could play a central role," said Daven Henze, an associate professor in the department of mechanical engineering at the University of Colorado at Boulder.

A Pathfinder Mission

"TES was a pioneer, collecting a whole new set of measurements with new techniques, which are now being used by a new generation of instruments," Bowman said. Its successor instruments are used for both atmospheric monitoring and weather forecasting. Among them are the National Oceanic and Atmospheric Administration's Cross-track Infrared Sounder (CrIS) instrument on the NOAA-NASA Suomi-NPP satellite and the Infrared Atmospheric Sounding Interferometer (IASI) series, developed by the French space agency in partnership with EUMETSAT, the European meteorological satellite organization.

Cathy Clerbaux, a senior scientist with the French Centre National de la Recherche Scientifique who is the leading scientist on the IASI series, said, "TES's influence on later missions like ours was very important. TES demonstrated the possibility of deriving the concentration of atmospheric gases by using interferometry to observe their molecular properties. Although similar instruments existed to sound the upper atmosphere, TES was special in allowing measurements nearer the surface, where pollution lies. The scientific results obtained with IASI greatly benefited from the close collaboration we developed with the TES scientists."

TES scientists have been pioneers in another way: by combining the instrument's measurements with those of other instruments to produce enhanced data sets, revealing more than either original set of observations. For example, combining the Ozone Monitoring Instrument on Aura's measurements in ultraviolet wavelengths with TES's thermal infrared measurements gives a data set with enhanced sensitivity to air pollutants near the surface.

The team is now applying that capability to measurements by other instrument pairs - for example, enhanced carbon monoxide (CO) from CrIS with CO and other measurements from the TROPOspheric Monitoring Instrument (TROPOMI) on the European Space Agency's Copernicus Sentinel-5 Precursor satellite. "The application of the TES algorithms to CrIS and TROPOMI data will continue the 18-year record of unique near-surface carbon monoxide measurements from [NASA's Terra' satellite's Measurement of Pollution in the Troposphere instrument, or MOPITT] into the next decade," said Helen Worden, a scientist at the National Center for Atmospheric Research in Boulder, Colorado, who is both the principal investigator of MOPITT and a TES science team member.

These new techniques developed for TES along with broad applications throughout the Earth System assure that the mission's legacy will continue long after TES's final farewell.

News Media Contact

Alan Buis

Jet Propulsion Laboratory, Pasadena, California

818-354-0474

Alan.Buis@jpl.nasa.gov

Written by Carol Rasmussen

NASA's Earth Science News Team

2018-031

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New Study Finds Sea Level Rise Accelerating

The rate of global sea level rise has been accelerating in recent decades, rather than increasing steadily, according to a new study based on 25 years of NASA and European satellite data.

This acceleration, driven mainly by increased melting in Greenland and Antarctica, has the potential to double the total sea level rise projected by 2100 when compared to projections that assume a constant rate of sea level rise, according to lead author Steve Nerem. Nerem is a professor of Aerospace Engineering Sciences at the University of Colorado Boulder, a fellow at Colorado's Cooperative Institute for Research in Environmental Sciences (CIRES), and a member of NASA's Sea Level Change team.

If the rate of ocean rise continues to change at this pace, sea level will rise 26 inches (65 centimeters) by 2100 -- enough to cause significant problems for coastal cities, according to the new assessment by Nerem and colleagues from NASA's Goddard Space Flight Center in Greenbelt, Maryland; CU Boulder; the University of South Florida in Tampa; and Old Dominion University in Norfolk, Virginia. The team, driven to understand and better predict Earth's response to a warming world, published their work Feb. 12 in the journal Proceedings of the National Academy of Sciences.

"This is almost certainly a conservative estimate," Nerem said. "Our extrapolation assumes that sea level continues to change in the future as it has over the last 25 years. Given the large changes we are seeing in the ice sheets today, that's not likely."

Rising concentrations of greenhouse gases in Earth's atmosphere increase the temperature of air and water, which causes sea level to rise in two ways. First, warmer water expands, and this "thermal expansion" of the ocean has contributed about half of the 2.8 inches (7 centimeters) of global mean sea level rise we've seen over the last 25 years, Nerem said. Second, melting land ice flows into the ocean, also increasing sea level across the globe.

These increases were measured using satellite altimeter measurements since 1992, including the Topex/Poseidon, Jason-1, Jason-2 and Jason-3 satellite missions, which have been jointly managed by multiple agencies, including NASA, Centre national d'etudes spatiales (CNES), European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and the National Oceanic and Atmospheric Administration (NOAA). NASA's Jet Propulsion Laboratory in Pasadena, California, manages the U.S. portion of these missions for NASA's Science Mission Directorate. The rate of sea level rise in the satellite era has risen from about 0.1 inch (2.5 millimeters) per year in the 1990s to about 0.13 inches (3.4 millimeters) per year today.

"The Topex/Poseidon/Jason altimetry missions have been essentially providing the equivalent of a global network of nearly half a million accurate tide gauges, providing sea surface height information every 10 days for over 25 years," said Brian Beckley, of NASA Goddard, second author on the new paper and lead of a team that processes altimetry observations into a global sea level data record. "As this climate data record approaches three decades, the fingerprints of Greenland and Antarctic land-based ice loss are now being revealed in the global and regional mean sea level estimates."

Even with a 25-year data record, detecting acceleration is challenging. Episodes like volcanic eruptions can create variability: the eruption of Mount Pinatubo in 1991 decreased global mean sea level just before the Topex/Poseidon satellite launch, for example. In addition, global sea level can fluctuate due to climate patterns such as El Ninos and La Ninos (the opposing phases of the El Nino-Southern Oscillation), which influence ocean temperature and global precipitation patterns.

Nerem and his team used climate models to account for the volcanic effects and other datasets to determine the El Nino/La Nina effects, ultimately uncovering the underlying rate and acceleration of sea level rise over the last quarter century.

The team also used tide gauge data to assess potential errors in the altimeter estimate.

"The tide gauge measurements are essential for determining the uncertainty in the global mean sea level acceleration estimate," said co-author Gary Mitchum, University of South Florida College of Marine Science. "They provide the only assessments of the satellite instruments from the ground." Others have used tide gauge data to measure sea level acceleration, but scientists have struggled to pull out other important details from tide-gauge data, such as changes in the last couple of decades due to more active ice sheet melt.

In addition to NASA's involvement in missions that make direct sea level observations from space, the agency's Earth science work includes a wide-ranging portfolio of missions, field campaigns and research that contribute to improved understanding of how global sea level is changing. Airborne campaigns such as Operation IceBridge and JPL's Oceans Melting Greenland gather measurements of ice sheets and glaciers, while computer modeling research improves our understanding of how Antarctica and Greenland will respond in a warming climate.

In 2018, NASA will launch two new satellite missions that will be critical to improving future sea level projections: the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a partnership with GeoForschungsZentrum (GFZ) in Germany, will continue measurements of the mass of the Greenland and Antarctic ice sheets; while the Ice, Cloud, and land Elevation Satellite-2 (ICESat-2) will make highly accurate observations of the elevation of ice sheets and glaciers.

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Written by Katie Weeman

Cooperative Institute for Research in Environmental Sciences

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Patrick Lynch

NASA's Goddard Space Flight Center, Greenbelt, Md.

Alan Buis

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-0474

Alan.Buis@jpl.nasa.gov

2018-029

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Texas Students to Speak with NASA Astronaut on Space Station

Students from Highland Village, Texas, will speak with a NASA astronaut living, working and doing research aboard the International Space Station at 1:10 p.m. EST Wednesday, Feb. 14.

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NASA Updates Russian Space Station Cargo Ship Launch, Docking Coverage

Loaded with three tons of food, fuel and supplies, a Russian Progress cargo spacecraft is scheduled to launch at 3:13 a.m. EST (2:13 p.m. Baikonur time) Tuesday, Feb. 13, to resupply the International Space Station.

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NASA Acting Administrator Statement on Fiscal Year 2019 Budget Proposal

Statement from acting NASA Administrator Robert Lightfoot on the Fiscal Year 2019 agency budget proposal.

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Texas Educators to Speak with NASA Astronaut on Space Station

Pre-service teachers from Houston, Texas, will speak with a NASA astronaut living, working and doing research aboard the International Space Station at 11:35 a.m. EST Tuesday, Feb. 13.

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Mars Reconnaissance Orbiter Preparing for Years Ahead

NASA's Mars Reconnaissance Orbiter (MRO) has begun extra stargazing to help the space agency accomplish advances in Mars exploration over the next decade.

The spacecraft already has worked more than double its planned mission life since launch in 2005. NASA plans to keep using it past the mid-2020s. Increased reliance on a star tracker, and less on aging gyroscopes, is one way the mission is adapting to extend its longevity. Another step is wringing more useful life from batteries. The mission's extended service provides data relay from assets on Mars' surface and observations with its science instruments, despite some degradation in capabilities.

"We know we're a critical element for the Mars Program to support other missions for the long haul, so we're finding ways to extend the spacecraft's life," said MRO Project Manager Dan Johnston of NASA's Jet Propulsion Laboratory, Pasadena, California. "In flight operations, our emphasis is on minimizing risk to the spacecraft while carrying out an ambitious scientific and programmatic plan." JPL partners with Lockheed Martin Space, Denver, in operating the spacecraft.

In early February, MRO completed its final full-swapover test using only stellar navigation to sense and maintain the spacecraft's orientation, without gyroscopes or accelerometers. The project is evaluating the recent test and planning to shift indefinitely to this "all-stellar" mode in March.

From MRO's 2005 launch until the "all-stellar" capability was uploaded as a software patch last year, the spacecraft always used an inertial measurement unit -- containing gyros and accelerometers -- for attitude control. At Mars, the orbiter's attitude changes almost continuously, with relation to the Sun and other stars, as it rotates once per orbit to keep its science instruments pointed downward at Mars.

The spacecraft carries a spare inertial measurement unit. The mission switched from the primary unit to the spare after about 58,000 hours of use, when the primary began showing signs of limited life several years ago. The spare shows normal life progression after 52,000 hours, but now needs to be conserved for when it will be most needed, while the star tracker handles attitude determination for routine operations.

The star tracker, which also has a backup on board, uses a camera to image the sky and pattern-recognition software to discern which bright stars are in the field of view. This allows the system to identify the spacecraft's orientation at that moment. Repeating the observations up to several times per second very accurately provides the rate and direction of attitude change.

"In all-stellar mode, we can do normal science and normal relay," Johnston said. "The inertial measurement unit powers back on only when it's needed, such as during safe mode, orbital trim maneuvers, or communications coverage during critical events around a Mars landing." Safe mode is a precautionary status the spacecraft enters when it senses unexpected conditions. Precise attitude control is then essential for maintaining communications with Earth and keeping the solar array facing the Sun for power.

To prolong battery life, the project is conditioning the two batteries to hold more charge, reducing demand on the batteries, and is planning to reduce the time the orbiter spends in Mars' shadow, when sunlight can't reach the solar arrays. The spacecraft uses its batteries only when it is in shadow, currently for about 40 minutes of every two-hour orbit.

The batteries are recharged by the orbiter's two large solar arrays. The mission now charges the batteries higher than before, to increase their capacity and lifespan. It has reduced the draw on them, in part by adjusting heater temperatures before the spacecraft enters shadow. The adjustment preheats vital parts while solar power is available so the heaters' drain on the batteries, while in shadow, can be reduced.

The near-circle of MRO's orbit stays at nearly the same angle to the Sun, as Mars orbits the Sun and rotates beneath the spacecraft. By design, as the orbiter passes over the sunlit side of the planet during each orbit, the ground beneath it is about halfway between noon and sunset. By shifting the orbit to later in the afternoon, mission managers could reduce the amount of time the spacecraft spends in Mars' shadow each orbit. NASA's Mars Odyssey spacecraft, older than MRO, successfully did this a few years ago. This option to extend battery life would not be used until after MRO has supported new Mars mission landings in 2018 and 2021 by receiving transmissions during the landers' critical arrival events.

"We are counting on Mars Reconnaissance Orbiter remaining in service for many more years," said Michael Meyer, lead scientist of NASA's Mars Exploration Program at the agency's Washington headquarters. "It's not just the communications relay that MRO provides, as important as that is. It's also the science-instrument observations. Those help us understand potential landing sites before they are visited, and interpret how the findings on the surface relate to the planet as a whole."

MRO continues to investigate Mars with all six of the orbiter's science instruments, a decade after what was initially planned as a two-year science mission to be followed by a two-year relay mission. More than 1,200 scientific publications have been based on MRO observations. Teams operating the two instruments named most often in research papers -- the High Resolution Imaging Science Experiment (HiRISE) camera and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) mineral-mapper -- are dealing with challenges but are ready to continue providing valuable observations.

For example, some HiRISE images taken in 2017 and early 2018 show slight blurring not seen earlier in the mission. The cause is under investigation. The percentage of full-resolution images with blurring peaked at 70 percent last October, at about the time when Mars was at the point in its orbit farthest from the Sun. The percentage has since declined to less than 20 percent. Even before the first blurred images were seen, observations with HiRISE commonly used a technique that covers more ground area at half the resolution. This still provides higher resolution than any other camera orbiting Mars -- about 2 feet (60 centimeters) per pixel -- and little blurring has appeared in the resulting images.

Using two spectrometers, CRISM can detect a wide range of minerals on Mars. The longer-wavelength spectrometer requires cooling to detect signatures of many minerals, including some associated with water, such as carbonates. To do this during the two-year prime science mission, CRISM used three cryocoolers, one at a time, to keep detectors at minus 235 Fahrenheit (minus 148 Celsius) or colder. A decade later, two of the cryocoolers no longer work. The last has become unreliable, but is still under evaluation after 34,000 hours of operation. Without a cryocooler, CRISM can still observe some near-infrared light at wavelengths valuable for detecting iron oxide and sulfate minerals that indicate past wet environments on Mars.

The Context Camera (CTX) continues as it has throughout the mission, adding to near-global coverage and searching for changes on the surface. The Shallow Radar (SHARAD) continues to probe the subsurface of Mars, looking for layering and ice. Two instruments for studying the atmosphere -- the Mars Color Imager (MARCI) and Mars Climate Sounder (MCS) -- continue to build on nearly six Mars years (about 12 Earth years) of recording weather and climate.

The University of Arizona operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, leads MRO's CRISM investigation. The Italian Space Agency provided SHARAD. Malin Space Science Systems, San Diego, built and operates CTX and MARCI. JPL, a division of Caltech in Pasadena, California, manages the MRO Project for the NASA Science Mission Directorate in Washington and leads the MCS investigation. Lockheed Martin Space built the spacecract.

News Media Contact

Guy Webster / Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-6278 / 818-393-2433

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Laurie Cantillo / Dwayne Brown

NASA Headquarters, Washington

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2018-028

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NASA Hosts News Conference, Interviews with Crew Launching to Space Station in June

NASA astronaut Serena Auñón-Chancellor, along with Alexander Gerst of ESA (European Space Agency), and Sergey Prokopyev of the Russian space agency Roscosmos, will participate in a news conference 2 p.m. EST Wednesday, Feb. 14, at NASA’s Johnson Space Center in Houston.

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Feb. 12 ‘State of NASA’ Events Highlight Agency Goals for Space Exploration

NASA centers across the country are opening their doors Monday, Feb. 12, to media and social media for “State of NASA” events, including a speech from acting NASA Administrator Robert Lightfoot, and unique opportunities for a behind-the-scenes look at the agency’s work.

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3-D Printable Tools May Help Study Astronaut Health

If humans are destined for deep space, they need to understand the space environment changes health, including aging and antibiotic resistance.

A new NASA project could help. It aims to develop technology used to study "omics" -- fields of microbiology that are important to human health. Omics includes research into genomes, microbiomes and proteomes.

The Omics in Space project is being led by NASA's Jet Propulsion Laboratory in Pasadena, California. The project was recently funded by NASA's Translational Research Institute for Space Health four years of study. Over that time, NASA hopes to develop 3-D printable designs for instruments on the International Space Station (ISS), that can handle liquids like blood samples without spilling in microgravity. These tools could enable astronauts to analyze biological samples without sending them back to Earth.

Learning how bacteria affect crew health, or how genes affect aging and disease, can ensure the safety of long-term missions to Mars and beyond.

No Overnight Mail in Space

NASA has already studied omics with efforts like the Microbial Tracking 1 experiment, which examined microbial diversity on the space station. But there's no way to process samples on the station right now, so they have to be sent down to Earth.

It can be months between the time a sample is taken and an analysis is done, said Kasthuri Venkateswaran of JPL, principal investigator for the Omics in Space project.

"You don't have overnight mail when you go to space," Venkateswaran said. "You have to do all the analysis by yourself. This project will develop an automated system for studying molecular biology with minimal crew intervention."

One of the biggest challenges with preparing samples is handling fluids in microgravity. Astronauts collect a variety of samples, including their own saliva and blood, as well as microbes swabbed from the walls of the ISS. These samples have to then be mixed with water so they can be injected into instruments for analysis. Without the proper tools, samples can spill, float or form air bubbles that could compromise results.

A Big Step in 2016

Last year, NASA took a big step by sequencing DNA in space for the first time. Astronauts used a tiny, handheld sequencing tool called the MinION, developed by Oxford Nanopore Technologies.

Omics in Space will build on this success by developing an automated DNA/RNA extractor which will prepare samples for aMinION device. A critical part of this extractor is a 3-D printable plastic cartridge needed to extract nucleic acids from the samples for the MinION sequencing.

All of this technology has been tested here on Earth, said Camilla Urbaniak, a post-doctoral researcher at JPL and co-investigator on Omics in Space.

"We're taking what's on Earth to analyze DNA and consolidating all the steps into an automated system," Urbaniak said. "What's new is we're developing a one-stop-shop that can extract and process all of these samples."

The Future of Space Health

Previous omics research has revealed that astronaut immune systems tend to be weaker after living on the ISS. Scientists aren't sure why.

The field of epigenetics, which studies how genes are expressed -- including how humans age -- could help explain how microgravity and cosmic rays affect our DNA.

But Omics in Space isn't just about the human passengers who travel to the ISS. There are also microbes, carried by humans and cargo alike, which accumulate on board spacecraft.

"We need to put together a 'passenger list' of the microbes that ride along to space," said Nitin Singh of JPL, another co-investigator on the project. "Then, astronauts can detect genetic markers revealing whether these microbes are helpful or harmful -- the 'luggage' these passengers are bringing with them."

Being able to respond to changes in a crew's environment is crucial during long space voyages, said Ganesh Mohan of JPL, a co-investigator on the project who will be working to detect pathogenic microbes.

"You can see whether a possibly harmful microbe is increasing in number in real time. If needed, we could then take actions to counteract those microbes," said Mohan.

The Omics in Space project is funded by NASA's Translational Research Institute for Space Health, which is jointly operated with the Baylor College of Medicine in Houston, Texas. The institute is overseen by NASA's Human Research Program.

Caltech in Pasadena, California manages JPL for NASA.

News Media Contact

Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433

andrew.c.good@jpl.nasa.gov

2018-027

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Tiny Crystal Shapes Get Close Look From Mars Rover

Star-shaped and swallowtail-shaped tiny, dark bumps in fine-layered bright bedrock of a Martian ridge are drawing close inspection by NASA's Curiosity Mars rover.

This set of shapes looks familiar to geologists who have studied gypsum crystals formed in drying lakes on Earth, but Curiosity's science team is considering multiple possibilities for the origin of these features on "Vera Rubin Ridge" on Mars.

One uncertainty the rover's inspection may resolve is the timing of when the crystal-shaped features formed, relative to when layers of sediment accumulated around them. Another is whether the original mineral that crystallized into these shapes remains in them or was subsequently dissolved away and replaced by something else. Answers may point to evidence of a drying lake or to groundwater that flowed through the sediment after it became cemented into rock.

The rover team also is investigating other clues on the same area to learn more about the Red Planet's history. These include stick-shaped features the size of rice grains, mineral veins with both bright and dark zones, color variations in the bedrock, smoothly horizontal laminations that vary more than tenfold in thickness of individual layers, and more than fourfold variation in the iron content of local rock targets examined by the rover.

"There's just a treasure trove of interesting targets concentrated in this one area," said Curiosity Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California. "Each is a clue, and the more clues, the better. It's going to be fun figuring out what it all means."

Vera Rubin Ridge stands out as an erosion-resistant band on the north slope of lower Mount Sharp inside Gale Crater. It was a planned destination for Curiosity even before the rover's 2012 landing on the crater floor near the mountain. The rover began climbing the ridge about five months ago and has now reached the uphill, southern edge. Some features here might be related to a transition to the next destination area uphill, which is called the "Clay Unit" because of clay minerals detected from orbit.

The team drove the rover to a site called "Jura" in mid-January to examine an area where -- even in images from orbit -- the bedrock is noticeably pale and gray, compared to the red, hematite-bearing bedrock forming most of Vera Rubin Ridge.

"These tiny 'V' shapes really caught our attention, but they were not at all the reason we went to that rock," said Curiosity science-team member Abigail Fraeman of JPL. "We were looking at the color change from one area to another. We were lucky to see the crystals. They're so tiny, you don't see them until you're right on them."

The features are about the size of a sesame seed. Some are single elongated crystals. Commonly, two or more coalesce into V-shaped "swallowtails" or more complex "lark's foot" or star configurations. "These shapes are characteristic of gypsum crystals," said Sanjeev Gupta, a Curiosity science-team member at Imperial College, London, who has studied such crystals in rocks of Scotland. Gypsum is a form of calcium sulfate. "These can form when salts become concentrated in water, such as in an evaporating lake."

The finely laminated bedrock at Jura is thought to result from lakebed sedimentation, as has been true in several lower, older geological layers Curiosity has examined. However, an alternative to the crystals forming in an evaporating lake is that they formed much later from salty fluids moving through the rock. That is also a type of evidence Curiosity has documented in multiple geological layers, where subsurface fluids deposited features such as mineral veins.

Some rock targets examined in the Jura area have two-toned mineral veins that formed after the lake sediments had hardened into rock. Brighter portions contain calcium sulfate; darker portions contain more iron. Some of the features shaped like gypsum crystals appear darker than gypsum, are enriched in iron, or are empty. These are clues that the original crystallizing material may have been replaced or removed by later effects of underground water.

The small, stick-shaped features were first seen two days before Curiosity reached Jura. All raw images from Mars rovers are quickly posted online, and some showing the "sticks" drew news-media attention comparing them to fossils. Among the alternative possibilities is that they are bits of the dark vein material. Rover science team members have been more excited about the swallowtails than the sticks.

"So far on this mission, most of the evidence we've seen about ancient lakes in Gale Crater has been for relatively fresh, non-salty water," Vasavada said. "If we start seeing lakes becoming saltier with time, that would help us understand how the environment changed in Gale Crater, and it's consistent with an overall pattern that water on Mars became more scarce over time."

Such a change could be like the difference between freshwater mountain lakes, resupplied often with snowmelt that keeps salts diluted, and salty lakes in deserts, where water evaporates faster than it is replaced.

If the crystals formed inside hardened rock much later, rather than in an evaporating lake, they offer evidence about the chemistry of a wet underground environment.

"In either scenario, these crystals are a new type of evidence that builds the story of persistent water and a long-lived habitable environment on Mars," Vasavada said.

Variations in iron content in the veins, smaller features and surrounding bedrock might provide clues about conditions favorable for microbial life. Iron oxides vary in their solubility in water, with more-oxidized types generally less likely to be dissolved and transported. An environment with a range of oxidation states can provide a battery-like energy gradient exploitable by some types of microbes.

"In upper Vera Rubin Ridge, we see clues that there were fluids carrying iron and, through some mechanism, the iron precipitated out," Fraeman said. "There was a change in fluid chemistry that could be significant for habitability."

For more about NASA's Curiosity Mars rover mission, visit:

https://mars.jpl.nasa.gov/msl

News Media Contact

Guy Webster / Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-6278 / 818-393-2433

guy.webster@jpl.nasa.gov / andrew.c.good@jpl.nasa.gov

Laurie Cantillo / Dwayne Brown

NASA Headquarters, Washington

202-358-1077 / 202-358-1726

laura.l.cantillo@nasa.gov / dwayne.c.brown@nasa.gov

2018-026

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NASA TV to Air US Spacewalk at the International Space Station

Two astronauts will venture outside the International Space Station Thursday, Feb. 15, to move components for the station’s robotic system into long-term storage. Live coverage of the spacewalk will begin at 5:30 a.m. EST on NASA Television and the agency’s website.

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NASA to Air Russian Space Station Cargo Ship Launch, Docking

Loaded with three tons of food, fuel and supplies, a Russian Progress cargo spacecraft is scheduled to launch at 3:58 a.m. EST (2:58 p.m. Baikonur time) Sunday, Feb. 11, to resupply the International Space Station.

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NASA Tests Atomic Clock for Deep Space Navigation

In deep space, accurate timekeeping is vital to navigation, but many spacecraft lack precise timepieces on board. For 20 years, NASA's Jet Propulsion Laboratory in Pasadena, California, has been perfecting a clock. It's not a wristwatch; not something you could buy at a store. It's the Deep Space Atomic Clock (DSAC), an instrument perfect for deep space exploration.

Currently, most missions rely on ground-based antennas paired with atomic clocks for navigation. Ground antennas send narrowly focused signals to spacecraft, which, in turn, return the signal. NASA uses the difference in time between sending a signal and receiving a response to calculate the spacecraft's location, velocity and path.

This method, though reliable, could be made much more efficient. For example, a ground station must wait for the spacecraft to return a signal, so a station can only track one spacecraft at a time. This requires spacecraft to wait for navigation commands from Earth rather than making those decisions on board and in real-time.

"Navigating in deep space requires measuring vast distances using our knowledge of how radio signals propagate in space," said Todd Ely of JPL, DSAC's principal investigator. "Navigating routinely requires distance measurements accurate to a meter or better. Since radio signals travel at the speed of light, that means we need to measure their time-of-flight to a precision of a few nanoseconds. Atomic clocks have done this routinely on the ground for decades. Doing this in space is what DSAC is all about."

The DSAC project aims to provide accurate onboard timekeeping for future NASA missions. Spacecraft using this new technology would no longer have to rely on two-way tracking. A spacecraft could use a signal sent from Earth to calculate position without returning the signal and waiting for commands from the ground, a process that can take hours. Timely location data and onboard control allow for more efficient operations, more precise maneuvering and adjustments to unexpected situations.

This paradigm shift enables spacecraft to focus on mission objectives rather than adjusting their position to point antennas earthward to close a link for two-way tracking.

Additionally, this innovation would allow ground stations to track multiple satellites at once near crowded areas like Mars. In certain scenarios, the accuracy of that tracking data would exceed traditional methods by a factor of five.

DSAC is an advanced prototype of a small, low-mass atomic clock based on mercury-ion trap technology. The atomic clocks at ground stations in NASA's Deep Space Network are about the size of a small refrigerator. DSAC is about the size of a four-slice toaster, and could be further miniaturized for future missions.

The DSAC test flight will take this technology from the laboratory to the space environment. While in orbit, the DSAC mission will use the navigation signals from U.S. GPS coupled with precise knowledge of GPS satellite orbits and clocks to confirm DSAC's performance. The demonstration should confirm that DSAC can maintain time accuracy to better than two nanoseconds (.000000002 seconds) over a day, with a goal of achieving 0.3 nanosecond accuracy.

Once DSAC has proved its mettle, future missions can use its technology enhancements. The clock promises increased tracking data quantity and improved tracking data quality. Coupling DSAC with onboard radio navigation could ensure that future exploration missions have the navigation data needed to traverse the solar system.

Technologies aboard DSAC could also improve GPS clock stability and, in turn, the service GPS provides to users worldwide. Ground-based test results have shown DSAC to be upwards of 50 times more stable than the atomic clocks currently flown on GPS. DSAC promises to be the most stable navigation space clock ever flown.

"We have lofty goals for improving deep space navigation and science using DSAC," said Ely. "It could have a real and immediate impact for everyone here on Earth if it's used to ensure the availability and continued performance of the GPS system."

DSAC is a partnership between NASA's Space Technology Mission Directorate and the Space Communications and Navigation program office, a program under the Human Exploration and Operations Mission Directorate. DSAC will launch in 2018 as a hosted payload on General Atomic's Orbital Test Bed spacecraft aboard the U.S. Air Force Space Technology Program (STP-2) mission.

For more information about DSAC, visit:

https://nasa.gov/mission_pages/tdm/clock

News Media Contact

Andrew Good

Jet Propulsion Laboratory, Pasadena, Calif.

818-393-2433

andrew.c.good@jpl.nasa.gov

Written by Danny Baird

NASA's Goddard Space Flight Center, Greenbelt, Md.

2018-024

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Two Small Asteroids Safely Pass Earth This Week

Two small asteroids recently discovered by astronomers at the NASA-funded Catalina Sky Survey (CSS) near Tucson, Arizona, are safely passing by Earth within one lunar distance this week.

The first of this week's close-approaching asteroids -- discovered by CSS on Feb. 4 -- is designated asteroid 2018 CC. Its close approach to Earth came Tuesday (Feb. 6) at 12:10 p.m. PST (3:10 p.m. EST) at a distance of about 114,000 miles (184,000 kilometers). The asteroid is estimated to be between 50 and 100 feet (15 and 30 meters) in size.

Of potentially greater interest is asteroid 2018 CB,which will also pass closely by Earth on Friday, Feb. 9, at around 2:30 p.m. PST (5:30 p.m. EST), at a distance of about 39,000 miles (64,000 kilometers), which is less than one-fifth the distance of Earth to the Moon). The asteroid, which is estimated to be between 50 and 130 feet (15 and 40 meters) in size, was also discovered by CSS on Feb. 4.

"Although 2018 CB is quite small, it might well be larger than the asteroid that entered the atmosphere over Chelyabinsk, Russia, almost exactly five years ago, in 2013," said Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory in Pasadena, California. "Asteroids of this size do not often approach this close to our planet -- maybe only once or twice a year."

JPL hosts the Center for Near-Earth Object Studies for NASA's Near-Earth Object Observations Program, an element of the Planetary Defense Coordination Office within the agency's Science Mission Directorate.

More information about asteroids and near-Earth objects can be found at:

https://cneos.jpl.nasa.gov

https://www.jpl.nasa.gov/asteroidwatch

For more information about NASA's Planetary Defense Coordination Office, visit:

https://www.nasa.gov/planetarydefense

For asteroid and comet news and updates, follow AsteroidWatch on Twitter:

twitter.com/AsteroidWatch

News Media Contact

DC Agle

818-393-9011

Jet Propulsion Laboratory, Pasadena, Calif.

agle@jpl.nasa.gov

2018-025

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Idaho Students to Speak with NASA Astronauts on Space Station

Students from Boise State University and Timberline High School in Boise, Idaho, will speak with NASA astronauts living, working and doing research aboard the International Space Station at noon EST Thursday, Feb. 8.

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New NASA Space Sensors to Address Key Earth Questions

Why is the Arctic warming faster than the rest of the planet? Does mineral dust warm or cool the atmosphere? NASA has selected two new, creative research proposals to develop small, space-based instruments that will tackle these fundamental questions about our home planet and its environment. NASA's Jet Propulsion Laboratory in Pasadena, California, is a key participant on both instruments.

The Polar Radiant Energy in the Far Infrared Experiment (PREFIRE) will fly a pair of small CubeSat satellites to probe a little-studied portion of the radiant energy emitted by Earth for clues about Arctic warming, sea ice loss and ice-sheet melting. Tristan L'Ecuyer of the University of Wisconsin, Madison, is the principal investigator.

The Earth Surface Mineral Dust Source Investigation (EMIT) will use a sensor mounted to the exterior of the International Space Station to determine the mineral composition ofnatural sources that produce dust aerosols around the world. By measuring in detail which minerals make up the dust, EMIT will help to answer the essential question of whether this type of aerosol warms or cools the atmosphere. Robert Green of JPL is the principal investigator.

These two instruments were competitively selected from 14 proposals considered under NASA's fourth Earth Venture Instrument opportunity. Earth Venture investigations are small, targeted science investigations that complement NASA's larger missions. The National Research Council recommended in 2007 that NASA undertake this type of regularly solicited, science-based, quick-turnaround project. The council's recently released decadal survey recommended the continuance of the program.

"PREFIRE and EMIT make innovative use of technologies first developed by NASA for planetary missions to address important, longstanding questions about Earth," said Michael Freilich, director of the Earth Science Division at NASA Headquarters in Washington.

The Arctic helps to regulate Earth's overall temperature by radiating back into space much of the excess energy from the Sun that is absorbed at lower latitudes. Current satellite instruments do not detect all of the wavelengths of this energy radiating from our planet. PREFIRE will fill in the current data gap at far-infrared wavelengths, collecting information that will help scientists diagnose the impact of this outgoing radiation on the Arctic region's energy balance.

PREFIRE will fly miniaturized thermal infrared spectrometers on two CubeSat satellites, each about the size of a loaf of bread. The sensors are based on technology previously flown on the Mars Climate Sounder, an instrument on NASA's Mars Reconnaissance Orbiter. The CubeSats will orbit Earth's poles to measure far-infrared emissions and how they change throughout the day and over seasons. The observations will allow scientists to assess how changes in thermal infrared emissions at the top of Earth's atmosphere are related to changes in cloud cover and surface conditions below, such as the amount of sea ice and meltwater on the surface of the ice.

The PREFIRE team brings together expertise in remote sensing, Earth system modeling and Arctic ice. JPL and the Space Dynamics Laboratory of North Logan, Utah, are mission partners. JPL is responsible for project management and is building and delivering the instrument. Brian Drouin of JPL is the deputy principal investigator, while JPL's Brian Kahn and Nicole-Jeanne Schlegel are co-investigators.

The composition of airborne dust particles is largely unknown, but it is a critical factor in determining whether mineral-based dust has a cooling or warming effect on the atmosphere. Scientists do not currently have a global inventory of the natural mineral sources of dust, and as a result the global impacts of dust on weather, atmospheric circulation and other aspects of Earth's environment are not well established.

EMIT's hyperspectral instrument will measure the different wavelengths of light emitted by minerals on the surface of deserts and other dust sources to determine their composition. The EMIT sensor is based in part on NASA's Moon Mineralogy Mapper instrument aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft.

The EMIT team brings together broad expertise that covers mineral measurements, soil science, remote sensing of surface properties and Earth system modeling. The project's modeling component will use the data collected to advance our understanding of the role of atmospheric dust in Earth's climate and better predict how it can be expected to change in the future.

Earth Venture missions provide an innovative approach to address Earth science research with regular windows of opportunity to accommodate new scientific priorities. The missions are managed by NASA's Earth System Science Pathfinder program, located at NASA's Langley Research Center in Hampton, Virginia, for the agency's Science Mission Directorate.

The first Earth Venture instruments headed to space are preparing for launch within the next year. The Global Ecosystem Dynamics Investigation (GEDI) and the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) will measure the distributions, canopy heights and changes in global vegetation from the space station, providing insights into how forests and ecosystems are affected by changes in water availability and other environmental and human factors.

For more information about the Earth Venture program, visit:

https://essp.nasa.gov

NASA uses the vantage point of space to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth's interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.

For more information about NASA's Earth science activities, visit:

https://www.nasa.gov/earth

News Media Contact

Alan Buis

Jet Propulsion Laboratory, Pasadena, California

818-354-0474

Alan.Buis@jpl.nasa.gov

Steve Cole

NASA Headquarters, Washington

202-358-0918

stephen.e.cole@nasa.gov

2018-023

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New NASA Space Sensors to Address Key Earth Science Questions

Why is the Arctic warming faster than the rest of the planet? Does mineral dust warm or cool the atmosphere? NASA has selected two new, creative research proposals to develop small, space-based instruments that will tackle these fundamental questions about our home planet and its environment.

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Combined Optics, Science Instruments of NASA’s James Webb Space Telescope Arrive in California

The two halves of NASA’s James Webb Space Telescope now reside at Northrop Grumman Aerospace Systems in Redondo Beach, California, where they will come together to form the complete observatory.

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Students in Peace Corps Program to Speak with NASA Astronauts on Space Station

Students from Washington, D.C., will speak with NASA astronauts living, working and doing research aboard the International Space Station at 12:55 p.m. EST Wednesday, Feb. 7.

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New Clues to Compositions of TRAPPIST-1 Planets

The seven Earth-size planets of TRAPPIST-1 are all mostly made of rock, with some having the potential to hold more water than Earth, according to a new study published in the journal Astronomy and Astrophysics. The planets' densities, now known much more precisely than before, suggest that some planets could have up to 5 percent of their mass in water -- which is 250 times more than the oceans on Earth.

The form that water would take on TRAPPIST-1 planets would depend on the amount of heat they receive from their star, which is a mere 9 percent as massive as our Sun. Planets closest to the star are more likely to host water in the form of atmospheric vapor, while those farther away may have water frozen on their surfaces as ice. TRAPPIST-1e is the rockiest planet of them all, but still is believed to have the potential to host some liquid water.

"We now know more about TRAPPIST-1 than any other planetary system apart from our own," said Sean Carey, manager of the Spitzer Science Center at Caltech/IPAC in Pasadena, California, and co-author of the new study. "The improved densities in our study dramatically refine our understanding of the nature of these mysterious worlds."

Since the extent of the system was revealed in February 2017, researchers have been working hard to better characterize these planets and collect more information about them. The new study offers better estimates than ever for the planets' densities.

What is TRAPPIST-1?

TRAPPIST-1 is named for the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) in Chile, which discovered two of the seven planets we know of today -- announced in 2016. NASA's Spitzer Space Telescope, in collaboration with ground-based telescopes, confirmed these planets and uncovered the other five in the system.

Since then, NASA's Kepler space telescope has also observed the TRAPPIST-1 system, and Spitzer began a program of 500 additional hours of TRAPPIST-1 observations, which will conclude in March. This new body of data helped study authors paint a clearer picture of the system than ever before -- although there is still much more to learn about TRAPPIST-1.

The TRAPPIST-1 planets huddle so close to one another that a person standing on the surface of one of these worlds would have a spectacular view of the neighboring planets in the sky. Those planets would sometimes appear larger than the Moon looks to an observer on Earth. They may also be tidally locked, meaning the same side of the planet is always facing the star, with each side in perpetual day or night. Although the planets are all closer to their star than Mercury is to the Sun, TRAPPIST-1 is such a cool star, some of its planets could still, in theory, hold liquid water.

In the new study, scientists led by Simon Grimm at the University of Bern in Switzerland created computer models to better simulate the planets based on all available information. For each planet, researchers had to come up with a model based on the newly measured masses, the orbital periods and a variety of other factors -- making it an extremely difficult, "35-dimensional problem," Grimm said. It took most of 2017 to invent new techniques and run simulations to characterize the planets' compositions.

What might these planets look like?

It is impossible to know exactly how each planet looks, because they are so far away. In our own solar system, the Moon and Mars have nearly the same density, yet their surfaces appear entirely different.

"Densities, while important clues to the planets' compositions, do not say anything about habitability. However, our study is an important step forward as we continue to explore whether these planets could support life," said Brice-Olivier Demory, co-author at the University of Bern.

Based on available data, here are scientists' best guesses about the appearances of the planets:

TRAPPIST-1b, the innermost planet, is likely to have a rocky core, surrounded by an atmosphere much thicker than Earth's. TRAPPIST-1c also likely has a rocky interior, but with a thinner atmosphere than planet b. TRAPPIST-1d is the lightest of the planets -- about 30 percent the mass of Earth. Scientists are uncertain whether it has a large atmosphere, an ocean or an ice layer -- all three of these would give the planet an "envelope" of volatile substances, which would make sense for a planet of its density.

Scientists were surprised that TRAPPIST-1e is the only planet in the system slightly denser than Earth, suggesting it may have a denser iron core than our home planet. Like TRAPPIST-1c, it does not necessarily have a thick atmosphere, ocean or ice layer -- making these two planets distinct in the system. It is mysterious why TRAPPIST-1e has a much rockier composition than the rest of the planets. In terms of size, density and the amount of radiation it receives from its star, this is the most similar planet to Earth.

TRAPPIST-1f, g and h are far enough from the host star that water could be frozen as ice across these surfaces. If they have thin atmospheres, they would be unlikely to contain the heavy molecules of Earth, such as carbon dioxide.

"It is interesting that the densest planets are not the ones that are the closest to the star, and that the colder planets cannot harbor thick atmospheres," said Caroline Dorn, study co-author based at the University of Zurich, Switzerland.

How do we know?

Scientists are able to calculate the densities of the planets because they happen to be lined up such that when they pass in front of their star, our Earth- and space-based telescopes can detect a dimming of its light. This is called a transit. The amount by which the starlight dims is related to the radius of the planet.

To get the density, scientists take advantage of what are called "transit timing variations." If there were no other gravitational forces on a transiting planet, it would always cross in front of its host star in the same amount of time -- for example, Earth orbits the Sun every 365 days, which is how we define one year. But because the TRAPPIST-1 planets are packed so close together, they change the timing of each other's "years" ever so slightly. Those variations in orbital timing are used to estimate the planets' masses. Then, mass and radius are used to calculate density.

Next Steps

The next step in exploring TRAPPIST-1 will be NASA's James Webb Space Telescope, which will be able to delve into the question of whether these planets have atmospheres and, if so, what those atmospheres are like. A recent study using NASA's Hubble Space Telescope found no detection of hydrogen-dominated atmospheres on planets TRAPPIST-1d, e and f -- another piece of evidence for rocky composition -- although the hydrogen-dominated atmosphere cannot be ruled out for g.

Illustrations of these worlds will change as ongoing scientificinvestigations home in on their properties.

"Our conceptions of what these planets look like today may change dramatically over time," said Robert Hurt, senior visualization scientist at the Spitzer Science Center. "As we learn more about these planets, the pictures we make will evolve in response to our improved understanding.

For more information about TRAPPIST-1, visit:

https://exoplanets.nasa.gov/trappist1

News Media Contact

Elizabeth Landau

Jet Propulsion Laboratory, Pasadena, CA

818-354-6425

elizabeth.landau@jpl.nasa.gov

2018-022

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