Variability of spider spatial configuration at the Martian south pole

Abstract

Araneiform terrain, or “spider” (spider-like surface modifications) is suggested to form through basal sublimation of seasonal translucent CO2 slab ice and subsequent gas jetting, and so far only known to occur at the Martian south pole. Their spatial configuration characteristics remain incompletely understood. We observed non-random spatial distributions in seven study regions with significant regional variation of average spacings. This non-randomness results from the pressure release by jetting from one spider, inhibiting ice rupture in the vicinity to initiate a new spider. Rose diagrams constructed from our trough orientation mapping show that spider troughs do not have preferred orientations and appear randomly distributed. We suggest that substrate properties such as permeability, porosity and cohesion regulate and modify the spatial configuration of a spider population on a regional scale, and insolation and obliquity determine whether general conditions are favorable for spider formation. The limited areal distribution of spiders may be due to the strict formation constraints on the thickness of the seasonal translucent CO2 slab ice. This work provides insight into the regional variability of gas jetting and spider formation.