Active pits on comet
Copyright; ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA;
graphic from J-B Vincent et al (2015). Hi-res image
Left: 18 pits have been identified in high-resolution OSIRIS images of Comet 67P/Churyumov–Gerasimenko’s northern hemisphere. The pits are named after the region they are found in, and some of them are active. The context image was taken on 3 August 2014 by the narrow-angle camera from a distance of 285 km; the image resolution is 5.3 m/pixel.
Middle,
top: close-up of the active pit named Seth_01 reveals small jets
emanating from the interior walls of the pit. The close-up also shows
the complex internal structure of the comet. The image is a section of
an OSIRIS wide-angle camera image capture on 20 October 2014 from a
distance of 7 km from the comet surface. Seth_01 measures about 220 m
across.
Right, top: context image showing fine structure in the
comet’s jets as seen from a distance of 28 km from the comet’s surface
on 22 November 2014. The image was taken with the OSIRIS wide-angle
camera and has a resolution is 2.8 m/pixel. In both images the contrast
is deliberately stretched in order to see the details of the activity.
The active pits in this study contribute a small fraction of the
observed activity.
Left, bottom: how the pits may form through
sinkhole collapse. 1. Heat causes subsurface ices to sublimate (blue
arrows), forming a cavity (2). When the ceiling becomes too weak to
support its own weight, it collapses, creating a deep, circular pit (3,
red arrow). Newly exposed material in the pit walls sublimates,
accounting for the observed activity (3, blue arrows).
Full story: Comet sinkholes generate jets
Source: ESA
