Eddie Brooks March 11, 2014 Earth 438 Rampart Craters: A Case for Water on Mars

Outline  What  What is a Rampart Crater?  Cratering Mechanics and Types  Why  Rampart Crater Formation Theory  Where  Rampart Craters on Mars  Location Implications  How  Resolving multiple theories

What is a Rampart Crater?  Fluidized ejecta  Can have multiple ejecta blankets  Very lobate  Not found on all planetary bodies  Most common of Martian crater morphologies

Rampart Cratering Mechanics  Impactor strikes ground  Kicks up cloud of ejecta  Either:  Atmosphere causes ejecta to fall in layers  Fluidized ejecta flows out in groups  Layered, lobate crater is formed

Formation Theories Make Rampart Craters Intriguing The existence of these craters may suggest the presence of large quantities of subsurface volatiles, including water.

Rampart Crater Types  Three types of Rampart Craters:  Single Layer Ejecta  Double Layer Ejecta  Multiple Layer Ejecta

Theories on Formation  Subsurface Volatiles:  Frozen materials heated upon impact  Volatiles melt and mix with surrounding terrain  Fluidized ejecta flows like mud  Theory supported by absence of rampart craters on dry Moon and Mercury  Atmospheric Conditions:  Atmosphere allows for generation of vortex ring  Staggers deposition of ejecta  Confirmed mechanics in laboratory setting  Theory supported by absence of craters on atmosphere-less Moon and Mercury

Where do the Craters Form?

Black – Rampart Craters Confirmed | White – Insufficient Data

Single Layer Ejecta

Double Layer Ejecta

Multiple Layer Ejecta

Implications of Locations  Rampart craters are not location dependent  Widespread across Mars Exception: Tharsis Region – geologically young  Crater type is location dependent  Subsurface volatile theory suggests correlation between frozen/liquid volatile and crater type  Atmospheric hypothesis alone lacks mechanism to explain location dependence

Reconciling Multiple Theories  Recent variations on atmospheric hypothesis incorporate volatiles to explain different crater types  Volatiles, when thrown into the air, may control descent into lobes  Raises the question: To what extent does the atmosphere play a role?  Enter: Ganymede and Europa

Ganymede and Europa  Planets without atmospheres  Water and other volatiles present  Rampart craters still form  Eliminates necessity of atmosphere for formation, emphasizes volatiles Ganymede

Conclusions and Further Work  Rampart craters are most likely the product of subsurface volatiles  Water is the most likely candidate, based on where craters are found  Further work can be performed to find out the exact influence an atmosphere may have on formation  Personal Project: Crater Catalogue