[meteorite-list] New Research Shows Impacts From Comet or Asteroids Could Have Created Europa's Chaos Terrain

[Ron Baalke]

http://blogs.agu.org/geospace/2015/10/14/new-research-shows-impacts-from-comets-or-asteroids-could-have-created-europas-chaos-terrain/

New research shows impacts from comets or asteroids could have created 
Europa's chaos terrain

By Mary Dettloff
14 October 2015

What began as Williams College students requesting a new course on planets 
and moons nearly 12 years ago has now culminated in a new research paper 
showing that impactors, such as comets or asteroids, can penetrate the 
frozen surface of Jupiter's moon Europa. The paper has been accepted for 
publication in the Journal of Geophysical Research: Planets, a publication 
of the American Geophysical Union.

Since 2004, undergraduate students led by Ronadh Cox, professor of geoscience, 
have studied the ice-covered surface of Europa, trying to understand the 
origins of its chaos terrain: areas that look like crustal breaches, with 
icebergs embedded in frozen slush. Cox's students explored various hypotheses 
for how these features might have formed, focusing on the possible role 
of impacts.

In 2009, student Aaron Bauer, a computer science major, took Cox's planetary 
tutorial course and became fascinated with this question. Bauer taught 
himself the programming language Fortran so that he could run numerical 
simulations to test the hypothesis that comets or asteroids had breached 
Europa's ice, exposing the underlying liquid ocean and possibly forming 
chaos terrain.

The modeling showed that ice penetration is possible for a range of situations. 
 For example, a half-kilometer diameter comet is capable of puncturing 
five kilometers of ice, whereas a five-kilometer comet could penetrate 
40 kilometers of ice.  The research also showed that no matter Europa's 
ice thickness, there is an impactor size with geologically reasonable 
recurrence that it is likely to breach it. This means that it is likely 
that Europa's ice-covered oceans were exposed often in the deep past, 
as well as in recent geological time.

Such penetrations would form conduits allowing the transfer of astrobiological 
material between the surface and the underlying ocean. Whether or not 
this is an important process on Europa - or whether it occurs at all – 
has not been established, but it could be important for Europa's potential 
to harbor life.

"How Europa's sub-ice surface ocean communicates with the surface, can 
mass and energy be transferred from the exterior to the liquid beneath 
and how thick the ice barrier is have been questions at the forefront 
of research since the Galileo data in the early 2000s revealed the probable 
existence of a liquid water layer," Cox said. "The research conducted 
by students about the breaches that occur in the ice could contribute 
to a better understanding of how they are caused."

The paper, co-authored by Bauer and Cox, will be presented at a Geological 
Society of America meeting in November.