MPS Seminar: Spring in Martian polar areas (G. Portyankina)

  • Datum: 13.05.2015
  • Uhrzeit: 14:00 - 15:00
  • Vortragende(r): Ganna Portyankina
  • Laboratory of Atmospheric and Space Physics, University of Colorado in Boulder, USA
  • Ort: MPS
  • Raum: Auditorium
  • Gastgeber: Wojciech Markiewicz
MPS Seminar: Spring in Martian polar areas (G. Portyankina)
Spring on Mars is a time of active changes in polar areas, at latitudes covered by seasonal CO2 ice. The High Resolution Imaging Science Experiment (HiRISE) on the Mars Reconnaissance Orbiter (MRO) has imaged five southern and four northern spring seasons. This temporal coverage allows studying seasonal changes in details, comparing phenomena in the south to the north, and one spring to the next. The volatile nature of the CO2 sublimation in spring leads to erosion and local redistribution of loose material on the surface. The best known and one of the most enigmatic examples of resulting terrain are so called araneiforms (shown in Fig. 1). Araneiforms are observed in southern polar areas only. They are believed to be troughs carved in the substrate by gaseous CO2, with the CO2 ice layer subliming from its bottom. In the northern hemisphere seasonal activity is mostly concentrated on the circumpolar dunes. When gaseous CO2 travels between seasonal ice layer and the dune surface, it creates furrows – channels so small, they get erased in summer by sand movement and created again in spring. The dark and bright fans, observed in both north and south polar areas (an example from the north is in Fig. 2) are a representation of the same phenomena. The fans are results of outbursts of CO2 gas coming from below CO2 ice layer dragging dust and sand with it. A hypothesis for creating the observed phenomena was proposed by H. Kieffer. It is based on the solid-state green house effect acting in the seasonal CO2 ice layer. The diversity of observed features in seasonal polar caps of Mars are produced when this process interacts with water ice, dust, and/or sand grains of the surface and the atmosphere. Most recent observations as well as modeling of spring activity on Mars and related experimental investigations will be discussed in the talk.
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