Science Seminars

4/24/2013-Special Seminar: Observations and modeling of gas sublimation-driven activity in Mars’ polar regions: CO2 jets and related erosion processes

Speaker: Ganna Portyankina (UCLA)
Date: Wednesday, Apr 24, 2013
Time: 4:00pm
Location: SPSC-W120

Seminar Abstract:

Martian polar areas are currently the most active regions of the planet. This is the place where geological changes are happening in today’s climate. Our recent publications explore the currently ongoing evolution of the landscape observed by spacecraft instruments. In the south polar regions enigmatic polar features commonly called araneiform terrain or, more colloquially, spiders are observed. Spiders are radially converging systems of branching troughs often exhibiting fractal properties. Areas where spiders have been found show substantial activity during local spring: the Mars Observer Camera (MOC) on the Mars Global Surveyor, and the High Resolution Imaging Science Experiment (HiRISE) and Context Imager (CTX) on the Mars Reconnaissance Orbiter have repeatedly observed dark and bright fans, seasonal cracks and non-linear temporal variations of the surface albedo in these areas. All of these features are believed to be related to a peculiar process of the spring sublimation of a seasonal CO2 ice layer called solid-state green house effect. Specific optical properties of CO2 slab ice allow solar energy to penetrate through the complete ice layer and start sublimation of CO2 from underneath the slab. The subliming CO2 increases the pressure below the ice slab and when this pressure reaches a particular critical value the slab ice breaks, releasing pressurized CO2 through the created opening. As the flux of gas moves underneath the ice towards the opening it rips off substrate material and transports it out of the sub-ice cavity creating a jet of CO2 gas with entrained sand and dust.

We conduct complex study campaign devoted to the above-described processes. The study includes observational campaigns by HiRISE and CRISM, computer modeling of the cold jet activity, related laboratory experiments, and crowdsourcing of the scientific activities to the public. I will present the most advanced results of the study.