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Project Progress

As first proposed by Murray and Malin (1973), shifts in the distribution of polar deposits on Mars may be the result of relatively recent true polar wander. Radar imaging of the Martian polar regions has confirmed that paleopolar deposits are offset from the present-day spin axis. To test the hypothesis that true polar wander is responsible for this offset, we have calculated the magnitude and direction of polar wander that would have been generated by relatively recent volcanic loads, such as Olympus Mons. Our findings, which have been submitted for publication, have implications for the internal evolution, past atmospheric pressure, and (through changes in wind regime) the geomorphology of Mars.

We have also established the age and time interval over which the Martian magnetic field disappeared. We used the MAG ER magnetic field map at an altitude of 185 km along with large impact basins mapped by Frey (2008) to determine which of the largest and oldest 21 impact basins are magnetized. We find that all are magnetized except the 5 youngest. This places tight constraints on the period over which the crust lost its ability to be magnetized. In Lillis et al. (2008) we suggest that the most straightforward explanation is that the core generated dynamo ceased. The crater-based model age is 4.16 Ga and the interval is 0.02 Ga.

We have also explored the development of oceans within the interior of icy satellites. We showed that erupting liquid water from such oceans is mechanically so difficult that it cannot occur on Europa and is unlikely to occur on Enceladus (Rudolph and Manga, 2008).