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

2. 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

3. 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

4. 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

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

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

7. 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

8. Where do the Craters Form?

9. Black – Rampart Craters Confirmed | White – Insufficient Data

10. Single Layer Ejecta

11. Double Layer Ejecta

12. Multiple Layer Ejecta

13. 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

14. 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

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

16. 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