Oceans on Mars?
Several lines of evidence suggest that an ocean might once have filled the northern lowlands of Mars, but topographic profiles along the margins of the lowlands do not follow surfaces of equal gravitational potential (i.e., sea level), as the shorelines of an ocean should. In a collaboration with Jerry Mitrovica (Harvard), Michael Manga (Berkeley), Mark Richards (U. Washington), Isamu Matsuyama (U. Arizona), and Amy Daradich (U. Toronto), we showed that these long-wavelength topographic trends can be explained by deformation that occurred in response to true polar wander (TPW), a reorientation of the planet with respect to its rotation axis.
Erik Chan, Jerry Mitrovica, Natalya Gomez (McGill) and Taylor Perron later revisited this question by analyzing a different set of possible sea level markers on Mars: the networks of river valleys that flowed to what would have been the shore of the ancient ocean. Erik found that the elevations of the downstream ends of these valley networks are consistent with the true polar wander path inferred from the shorelines themselves, perhaps with additional deformation due to the growing Tharsis volcanic bulge.
- Chan, N.-H., J.T. Perron, J.X. Mitrovica and N.A. Gomez (2018). New Evidence of an Ancient Martian Ocean from the Global Distribution of Valley Networks. JGR Planets, 123, 2138-2150, http://doi.org/10.1029/2018JE005536.
- Perron, J.T., J.X. Mitrovica, M. Manga, I. Matsuyama and M.A. Richards (2007), Evidence of an ancient martian ocean in the topography of deformed shorelines. Nature, 447, 840–843, http://doi.org/10.1038/nature05873.
- Daradich, A., J.X. Mitrovica, I. Matsuyama, J.T. Perron, M. Manga and M.A. Richards (2008), Equilibrium rotational stability and ﬁgure of Mars. Icarus, 194, 463–475, http://doi.org/10.1016/j.icarus.2007.10.017.
- Matsuyama, I., J.X. Mitrovica, M. Manga, J.T. Perron and M.A. Richards (2006), Rotational stability of dynamic planets with elastic lithospheres. J. Geophys. Res., 111, E02003, http://doi.org/10.1029/2005JE002447.