Laboratory simulations of Martian Southern Spring : the outcome of CO2 cold jets

Orbital data from the Colour and Stereo Surface Imaging System (CaSSIS) onboard the ExoMars Trace Gas Orbiter showed interesting images of the circumpolar areas during spring. The winter-formed dusty CO2 ice cap goes under self-cleaning processes producing a translucent slab. With grazing spring sunlight, it starts to sublimate at the base and from overpressure, cold jets erupt leaving erosion marks in the underlying substrate and dust/sand deposits at the surface. This model, proposed by Kieffer, is commonly accepted to explain dark spots and fans deposits as well as spiders.

To test different aspects of this model, we combine observational data from CaSSIS with experimental work for which Martian temperature and pressure at high latitudes could be reached in a simulation chamber. Preliminary results on sinking analogous dust material (MGS-1) on a CO2 ice slab have been promising. We aim to quantify in better details the sinking ratio, colour variations and frost (H2O and/or CO2) depositions on CO2/MGS-1 samples under various setup conditions (illumination, material distribution). Using a hyperspectral device, we can measure the reflectance and simulate the CaSSIS signal in the different filters (PAN, NIR, RED, BLU) to compare to actual images that have been acquired during southern spring.