Interpreting images – more on how the comet got its shape

On 28 September, a scientific paper was published in Nature, presenting a view on the formation scenario of Comet 67P/Churyumov-Gerasimenko, based on Rosetta OSIRIS images (read our news report here). The paper, led by Dr Matteo Massironi of the University of Padova, Italy, evaluated two possible models to explain the comet's curious shape: the merging of two cometesimals or the erosion of a single object. Observational data and thorough analysis of the comet's gravity field pointed towards the first of the two hypotheses: 67P/C-G seems to have originated from two separately formed comets that merged at low speed. The topic has generated a lot of discussion in the comments thread of this blog, in particular by proponents of an alternative explanation put forward by one of our blog readers Mr A. Cooper who suggests that the comet was once a single body that has since been stretched into two separate lobes. We asked Matteo to share his opinion not only on this subject but also on the general topic of how planetary images are interpreted in order to arrive at a robust scientific theory. Here is what he wrote: Sorry for my late reply, but I wanted some time to go through the blog where the stretching hypothesis is described before saying something about the supporting geological proofs. As a scientist, I do not normally read works that have not been rigorously reviewed and published in scientific journals. Probably that is my fault and I want to thank ESA to have created this interesting blog allowing so many people to be an active part of Rosetta’s discoveries. As a geologist, I would first like to point out some basic principles to follow when dealing with space images for geological interpretations. I believe these suggestions could be of some help to […]

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