We have spotted caves on a comet for the first time. The caves, identified on comet 67P/Churyumov-Gerasimenko 鈥� also known as comet 67P 鈥� are full of ice, which could help explain mysterious jets that astronomers have seen coming from the comet.
While we know roughly what comets are made of 鈥� commonly rock, ice and frozen gases 鈥� we don鈥檛 know much about their internal structure. Caves could offer an easy access point for scientists to learn about this interior, but unlike many planets and bodies in the solar system, caves hadn鈥檛 yet been spotted on a comet.
Now, at the French National Centre for Scientific Research and his colleagues have documented three ice-filled caves on comet 67P, using 3D reconstructions of the comet鈥檚 surface created from high-resolution photographs taken by the Rosetta spacecraft in 2016.
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Rosetta passed by the comet several times during its mission, but only images taken during its closest flybys, over a small section of 67P, were detailed enough to create 3D images. 鈥淭here鈥檚 no reason why there shouldn鈥檛 be more caves at other places, but we don鈥檛 have the right circumstances to see them,鈥� says Lamy.
Lamy and his team constructed the 3D images, known as anaglyphs, and built profiles of the caves, which they found extended into the comet from 20 to 47 metres deep.
They also realised that a bright jet emanating from the comet in July 2015, which probably contained ice, was released as light from the sun illuminated the bottom of one of the caves, suggesting a possible mechanism for the creation of the icy plume.
It isn鈥檛 yet clear what kind of ice is present inside the cavities, says at the University of Kent, UK, but if it is recently exposed water ice from the inside of the comet then it would 鈥渞epresent a great opportunity to study or sample an area that may be even more pristine than other areas of a comet鈥檚 surface鈥�, he says. However, landing a spacecraft in such a small area would be difficult, he adds.
arXiv
