Curiosity Blog, Sols 4995-5001: 5,000 (Martian) Days on Mars
NASA’s Mars rover Curiosity acquired this image along Chocolatal ripple using its Right Navigation Camera on Aug. 28, 2026 — Sol 4998, or Martian day 4,998 of the Mars Science Laboratory mission — at 13:58:36 UTC.
NASA/JPL-Caltech
Written by William Farrand, Senior Research Scientist, Space Science Institute
Earth planning date: Friday, Aug. 28, 2026
The span of sols spanned by this blog post is noteworthy in several ways. First, Curiosity became a world-class (for Mars at least) mountaineer by passing the 1 kilometer mark of elevation from its landing site on the floor of Gale crater. This writer was on the Mars Exploration Rover science team and we were excited when the Spirit rover got to the top of Husband Hill in Gusev crater in August 2005. But that was a climb of 106 meters (about 348 feet) above its landing site, and Curiosity has passed 1000 meters (about 0.62 miles).
Second, Saturday, Aug. 29, marked 5,000 Martian days (or sols) since Curiosity landed on Mars (that’s more than 5,137 Earth days, because a day on Mars lasts 24.6 hours). Congratulations are in order to the engineers and scientists who have made this landmark possible.
Finally, in terms of its science activities Curiosity is examining a wind-formed, long, narrow, large ripple which has been named “Chocolatal.” Further examination will help determine if this feature could be classified as a “transverse aeolian ridge” or TAR. TARs have been observed across the Martian surface based on orbital imaging. The long axis of a TAR is oriented perpendicular to the local predominant wind direction. While this is not the first potential TAR that has been examined by Curiosity, its location, higher on the slopes of Mount Sharp invites questions about whether it will be composed of the same types of granular materials found in the lower TARs, or whether it has a different range of grain sizes and/or layering.
Other questions to be addressed include how the ridge formed, whether it is active, how it has migrated, and, if it is immobile, then how has it stabilized?
At the start of the planning week, Curiosity was en route to the sand ripple and encountered interesting science targets along the way. In Monday’s two-sol plan, in-situ examinations were planned of the light-toned bedrock occurring along the rover’s path. Some of the rocks encountered near the rover had dark-toned thick coatings or remnant layers, and these were targeted for chemical examination by the rover’s ChemCam Laser Induced Breakdown Spectroscopy (LIBS) instrument. Mastcam and ChemCam Remote Micro Imager (RMI) mosaics were planned, for layers in buttes along the rover’s path, and on more distant sets of sand ripples.
A midweek planning session took advantage of the last drive, leaving the rover only a few meters from Chocolatal. ChemCam was able to target sand at the base of Chocolatal as well as nearby bedrock. Stand-off Mastcam high-resolution image mosaics of the ripple were also targeted. The drive planned midweek took the rover right into Chocolatal with one of its wheels and then backing off a little, so in the end-of-week plan, contact science could be planned within the trenched region.
The final planning session of the week, which extended through the landmark Sol 5000, involved MAHLI mosaics of the right wall of the trench to see if there is layering, and to assess any variations in grain size. It’s noteworthy that these MAHLI mosaics are being named in honor of our late colleague Paul Geissler, who was one of the foremost experts on the study of Martian TARs and who was working with the MAHLI team before his untimely passing earlier in the year. In-situ APXS measurements were planned of the coarse-grained surface of the ripple, and ChemCam LIBS measurements were planned on the top of Chocolatal, a sinuous feature looking like a “mohawk” haircut (see the accompanying image). LIBS was also planned on a dark band on its flank and at the back of the scuff/trench. Other activities in the three-sol plan included Mastcam mosaics, an AM Navcam dust-devil survey, Navcam suprahorizon survey, and APXS atmospheric measurements.
With 5000 sols of outstanding scientific accomplishments, the Curiosity science and engineering team looks forward to the next 5000 sols.
Anak Krakatau erupts ash and volcanic gases in this image acquired with the OLI (Operational Land Imager) on Landsat 8 on September 5, 2026.
NASA Earth Observatory/Michala Garrison
Eruptions are a regular occurrence at Anak Krakatau, a small volcano between the Indonesian islands of Java and Sumatra. Much of its activity remains relatively mild, but it occasionally puts on more impressive and hazardous shows of force. In early September 2026, a booming eruption lasting more than 24 hours sent gas and ash high into the atmosphere, disrupting thousands of flights and degrading air quality in parts of the country, including the capital city of Jakarta.
Satellites passing over the area during the eruption on September 5 captured images of the explosive activity. In the scene above, acquired with the OLI (Operational Land Imager) on the NASA-USGS Landsat 8 satellite, a white plume of volcanic gas billows over a brown ash cloud. Below, a wider view captured by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite shows the volcanic material dispersing over a large area.
Indonesia’s meteorological agency reported that ash had reached altitudes up to 6,000 meters (20,000 feet) to the east of the volcano and 15,000 meters (50,000 feet) to the west by September 6. The presence of ash in the atmosphere prompted the temporary closure of eight airports on Java and Sumatra, disrupting nearly 3,000 flights in and out of the area, according to news reports.
Plumes of ash and volcanic gases from Anak Krakatau drift over Indonesia and the Indian Ocean in this image captured by the VIIRS (Visible Infrared Imaging Radiometer Suite) on the Suomi NPP satellite on September 5, 2026.
NASA Earth Observatory/Michala Garrison
Ashfall affected populated areas, particularly to the east of Anak Krakatau in Jakarta and other parts of West Java, the Indonesian Humanitarian Coordination Platform (IHCP) reported. Volcanic ash poses health risks to people and can irritate the respiratory tract, eyes, and skin. However, this air quality hazard differs from the smoke produced by peatland fires elsewhere in the country in terms of particle characteristics, dispersal patterns, and protection measures, the IHCP noted.
On September 6, the continuous explosive eruption from Anak Krakatau subsided, though the volcano kept rumbling. It returned to a more typical pattern of Strombolian eruptions, characterized by intermittent spurts of ash and volcanic material. Airports had resumed operation by September 8, but the volcano remained at the second-highest alert level on the country’s scale, as it has been since early July.
Artistic concept of lunar surface technologies and infrastructure capabilities, including in-situ resource utilization oxygen production systems, surface power systems, in-space manufacturing tools, and advanced nanomaterials production.
Credit: NASA
NASA is seeking proposals to advance the technology and infrastructure needed to explore the Moon and establish a Moon Base in the lunar South Pole region.
Announced on Tuesday, Sept. 8, the solicitation targets capability gaps, including power generation, oxygen extraction, and producing materials on the Moon required for construction and operations. These technologies are essential to making humanity’s next great leap in lunar exploration.
“NASA is accelerating the development of key technologies and closing critical gaps needed for long-term human exploration at the Moon,” said Greg Stover, director of NASA’s Advanced Research and Technology Division. “Partnering with industry will strengthen the U.S. industrial base as we mature the capabilities and infrastructure needed for a sustainable lunar presence.”
The NextSTEP-3 Broad Agency Announcement Appendix A: Lunar Enabling Infrastructure Accelerator solicitation aims to mature and demonstrate capabilities in five areas:
Vertical solar array technology that can provide consistent power generation, management, distribution, and energy storage.
In-situ resource utilization oxygen from regolith production to extract usable oxygen molecularly bonded to rock and dust covering the Moon’s surface.
Radioisotope Stirling generator, a type of nuclear energy technology that uses heat from fissile materials to produce electric power for operating spacecraft systems in the darkest, dustiest, and most remote places.
In-space advanced manufacturing to reduce reliance on resupply missions from Earth and to optimize mission flexibility and resilience on the Moon.
Innovative nanomaterials production to advance the commercial availability and quality of nanomaterials that can be used in lunar exploration.
The solicitation intends to cultivate U.S.-led capabilities while maintaining full and open competition among private industry, academic institutions, and not‑for‑profit entities, as well as international partners participating through U.S.-led teams.
NASA may apply insights gained from the resulting contracts of this solicitation, such as technical data, and demonstration results, to shape future acquisition strategies.
NASA’s Hubble, Webb Find Far-out Solar System Objects ‘Remember’ Past
This artist’s concept depicts a Trans-Neptunian Object, a small, faint, icy body orbiting the Sun beyond the orbit of Neptune. These objects are so small that even with NASA’s Hubble and Webb space telescopes, they appear only as tiny points of light.
Artwork: NASA, ESA, Leah Hustak (STScI)
For the first time, scientists used the joint power of NASA’s Hubble and James Webb Space Telescopes to study some of the most far-flung bodies in our solar system, Trans-Neptunian Objects (TNOs). Some of these are the smallest and faintest ever directly seen. The researchers unexpectedly found fewer small TNOs than they expected, and that the colors of these bodies followed the same relationships as their larger family members.
These objects are typically small, faint, icy bodies orbiting the Sun beyond the orbit of Neptune. Most are more than 100 million times dimmer than objects visible to the unaided eye. In two complementary papers published Tuesday in The Astronomical Journal, teams analyzed the color, composition, and size distribution of 27 newly discovered tiny, dim TNOs.
This class of small bodies offers the best view into an early stage of planet-building, when a disk of dust and pebbles in orbit around the Sun coalesced into city-sized “planetesimals” — the solid building blocks that clump together to form planets — but had not yet merged into full-sized worlds. Beyond Neptune, this second stage never happened, leaving behind a frozen population of planetesimals.
In the deepest TNO survey to date, teams led by PhD candidates from the University of Victoria in Canada, under the guidance of the National Research Council of Canada, and Northern Arizona University in Flagstaff examined a patch of sky simultaneously with Hubble, observing the TNOs’ visible light, and Webb, observing their infrared light. The team of researchers measured the objects’ colors, which are like a fingerprint of the surface composition, as well as their sizes and determined their orbits.
In the coordinated observations, the teams studied two different types of TNOs. The first, dynamically “cold” TNOs, are on their original, relatively circular orbits around the Sun in the plane of the solar system. The second type, dynamically “hot” TNOs, formed between the current locations of Uranus and Neptune but were pushed outward where they are today when the outer gas giants migrated early in the solar system’s history. Today they reside in highly elliptical orbits and move in and out of the plane of our solar system.
NASA’s Goddard Space Flight Center; Lead Producer: Paul Morris
Prior to these observations, astronomers thought that small TNOs from both hot and cold populations would have undergone many collisions, changing their surfaces compared to larger TNOs. But that’s not what the observations showed. Instead, the small bodies look like their larger counterparts. This implies that collisions are not changing the surfaces significantly—perhaps because there are fewer collisions than expected, or because the TNOs somehow retain their primordial, pre-collision compositions. The teams are still trying to unravel this mystery.
“You could imagine a scenario where getting knocked around and fragmented would change the surface composition, and then you would see a different surface color for tiny TNOs compared to their larger siblings. So it’s really fascinating to see that the smallest objects are somehow ‘remembering’ and preserving the history of how they were made,” said Northern Arizona University PhD candidate Anastasia Morgan, who led the study of color and composition.
“These dynamically ‘hot’ TNOs retain a signature of where they were born, even though they’ve been orbitally scrambled since then,” said co-author David Trilling of Northern Arizona University.
Both the “hot” and “cold” populations seem to keep the same colors as when they were formed, with little change since the birth of the solar system.
The Webb data also allowed researchers to measure the number of objects of each size. They found that the overall size distributions for both populations were surprisingly similar.
“It’s very interesting that the process of planetesimal formation ends up producing the same distribution of sizes for both cold and hot populations, despite forming in different regions of the early solar system. The process seems to be insensitive to disk conditions, producing similar planetesimal sizes whether the disk is hot or cold, and dense or fluffy,” said University of Victoria PhD candidate Marielle Eduardo, who led the study on size distribution.
Researchers also found fewer of these very small bodies than they expected based on some planet formation models. Webb discovered 27 new, remarkably dim TNOs, one so faint it is equivalent to standing on Earth and seeing a small swarm of fireflies on the Moon. The smallest one they observed has a diameter of about 3 miles (5 kilometers), which is about five times smaller than what is possible to detect with the most sensitive ground-based telescopes.
This project would not have been possible without Hubble and Webb working together to detect and characterize these TNOs. With Hubble’s sensitivity in visible light and Webb’s in infrared, the space telescopes provide more insights than either can on its own.
The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space, based in Denver, also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).
This artist’s concept depicts a Trans-Neptunian Object, a small, faint, icy body orbiting the Sun beyond the orbit of Neptune. These objects are so small that even with NASA’s Hubble and Webb space telescopes, they appear only as tiny points of light.
Tiny Worlds Discovered by Hubble and Webb
This video explains how Hubble and Webb are giving scientists a new look at some of the solar system’s oldest survivors and revealing new clues about how the building blocks of planets, including Earth, first formed.
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NASA’s Webb Reveals the Ancient Surfaces of Trans-Neptunian Objects
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