Eddie BrooksMarch 11, 2014Earth 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 depositionof ejecta

Confirmed mechanics in laboratory setting

Theory supported by absence of craters on atmosphere-less Moon and Mercury

Where do the Craters Form?

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