2009 Annual Science Report
University of California, Berkeley Reporting | JUL 2008 – AUG 2009
Coupled Evolution of Mars' Surface Water and Interior
The delivery and availability of water on the Martian surface depends on the coupled evolution of the Martian interior and atmosphere. We developed models for the history of volcanism on Mars. We also determined the conditions under which the location of the Martian spin axis remains stable. We find that some true polar wander — motion of the spin axis — may have occurred, but not enough to explain the observed deformation of hypothesized shorelines that circumscribed a large paleo-ocean.
True polar wander on Mars can shift climate belts, complicating the interpretation of ancient (pre-polar wander) water-altered terrains. We calculated that recent (Hesperian through Amazonian) volcanism may have caused several degrees of polar wander—sufficient to account for offsets of paleopolar deposits from the present-day spin axis (Kite et al., EPSL 2009). To follow-up on this work, we have initiated a collaboration with the GCM group at NASA Ames/SETI (Bob Haberle, Lori Fenton, and Melinda Kahre) which has led to GCM simulations at Ames on our predicted pre-TPW topography.
We have initiated a new project on chaos storms – changes in winds, and precipitation, during formation of chaos terrain and outburst channels. If chaos storms and other short-lived events explain young dendritic channel networks on Mars, this would break the link between dendritic valley networks and surface climate conditions that could sustain life. Kite traveled to Southwest Research Institute, Boulder, to collaborate with Scot Rafkin and Tim Michaels (SwRI) on modifying Mars Regional Atmospheric Modelling System (MRAMS) to simulate chaos storms. Preliminary results with modified boundary conditions appropriate for a chaos-forming event produce high rates of snowfall on the margins of the chaos chasm, and indicated a need to treat water species (vapor, ice) as major atmospheric constituents, rather than as trace species as in the current version of MRAMS. Our preliminary results have been submitted for presentation at the AGU Fall Meeting in December 2009.
Graduate student Kite’s work on debris disks in young extrasolar planetary systems has led to an interest in how a massive asteroid belt could have shaped the orbit of Early Mars. A highly eccentric early Mars orbit would lead to strong insolation at perihelion, perhaps enough to bring the surface temperature above the triple point without a multi-bar CO2 atmosphere. We have initiated a side project on early Mars orbital dynamics, using n-body simulations to determine which high-eccentricity orbits are stable, and whether a route exists from a highly eccentric early Mars orbit to the moderate present-day eccentricity.
Finally, we used observations of the magnetic field above Mars, combined with models of magmatic intrusion and mantle convection to quantify the amount and timing of magma intrusion into the crust (Lillis et al., 2009) and proposed that large impacts were responsible for the death of the Martian dynamo (Lillis et al., 2008; Roberts et al., 2009). In turn, the loss of protection from the solar wind providing by the ancient Martian dynamo may have precipitated rapid loss of the Martian atmosphere.