The Formation of Araneiforms by Carbon Dioxide Venting and Vigorous
Sublimation Dynamics Under Martian Conditions
Abstract
The local redistribution of granular material by sublimation of the
southern seasonal CO2 ice deposit is one of the most active surface
shaping processes on Mars today. This unique geomorphic mechanism has
been linked to the dendritic, branching, ‘spider’-like araneiform
terrain and associated fans and spots - features which are native to
Mars and have no Earth analogues. However, there is a paucity of
empirical data to test the validity of this genetic hypothesis.
Additionally, it is unclear whether the organised radial patterns of
araneiforms require a singular or multiple seasonal events to form. Here
we present the results of a suite of laboratory experiments undertaken
to investigate if the interaction between a sublimating CO2 ice
overburden with central vents and a porous, mobile regolith will
mobilise grains from beneath the ice in the form of a plume to generate
araneiform patterns. We investigate the physical constraints on the
level of branching of these features and the area that they cover. We
provide the first observations of plume activity via CO2 sublimation and
consequent erosion of araneiform features. Based on calculations of the
mass flux sublimation rate of CO2 ice blocks buried under sediment and
consequent volume transport, we show that CO2 sublimation can be a
highly efficient agent of sediment transport under Martian pressure.