Carbon dioxide snowfalls, polar caps, and the climate of Mars

Paul Hayne; Jet Propulsion Laboratory

 Like the Earth, Mars experiences seasonal cycles due to its ~25-degree
axial tilt. Unlike the Earth, polar winter on Mars brings temperatures
cold enough to freeze out the atmosphere, in the form of carbon dioxide
surface frosts and snowfalls. The ice caps of Mars grow and shrink in
response to seasonal changes in the polar heat balance. Since 2006, we
have been monitoring the martian polar regions with multi-spectral thermal
infrared measurements acquired by the Mars Climate Sounder (MCS). From
these data, we retrieve vertical profiles of temperature and aerosol
opacity, as well as surface properties such as ice granularity and dust
content. This dataset provides an unprecedented view of the rich and
complex ice caps and polar atmosphere. In this talk, I will highlight the
dynamic polar processes at the heart of the martian CO2 cycle, as revealed
by MCS. We will see evidence for striking inter-annual repeatability,
diverse thermal and precipitation regimes, and intense localized
snowstorms. In light of these new observations, we will explore the
implications for the present and past climate of Mars.