Planetary Science Institute | 2018 Sep 10
The release of gases through sublimation is the defining process of comets, but a new paper by Planetary Science Institute Research Scientist Jordan K. Steckloff and Senior Scientist Nalin H. Samarasinha says that periodic landslides and avalanches, known as mass wasting, may be responsible for keeping comets active over a long time.
- The Rosetta spacecraft observed many mass wasting events on the surface of comet 67P/Churyumov-Gerasimenko, including this cliff in the Aswan region of the comet. The arrow denotes the same location in both images, showing a crack forming behind the cliff that preceded its collapse. Mass wasting debris is clearly visible at the base of the cliff. Image credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
These escaping gases loft dust off of the comet, forming a dust cloud visible from the Earth. This gas release can even change the spin state of the comet. However, this process has long been expected to shut down as the ice present at the surface of the comet sublimates away, leaving a dust layer at the surface that insulates the remaining subsurface ice. It has therefore been unknown how comets remain active, rather than fade into non-active objects.
... mass-wasting activity can excavate and expose buried ices to the surface of the comet , giving the comet fresh ice to sublimate. However, mass-wasting leads to a flattening of features on the surface of the comet over time, which in turn reduces the number and frequency of mass wasting events. ...
The Sublimative Torques of Jupiter Family Comets and Mass Wasting Events on Their Nuclei ~ Jordan K. Steckloff, Nalin H. Samarasinha