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Evidence for an ancient martian ocean in the topography of deformed shorelines


A suite of observations suggests that the northern plains of Mars, which cover nearly one third of the planet's surface, may once have contained an ocean1,2,3,4,5,6,7. Perhaps the most provocative evidence for an ancient ocean is a set of surface features that ring the plains for thousands of kilometres and that have been interpreted as a series of palaeoshorelines of different age1,7. It has been shown, however, that topographic profiles along the putative shorelines contain long-wavelength trends with amplitudes of up to several kilometres4,5,8, and these trends have been taken as an argument against the martian shoreline (and ocean) hypothesis8. Here we show that the long-wavelength topography of the shorelines is consistent with deformation caused by true polar wander—a change in the orientation of a planet with respect to its rotation pole—and that the inferred pole path has the geometry expected for a true polar wander event that postdates the formation of the massive Tharsis volcanic rise.

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Figure 1: Possible palaeoshorelines on Mars.
Figure 2: Changes in topography due to TPW.
Figure 3: TPW path that reconciles shoreline deformation.

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This work was supported by the NASA Astrobiology Institute (J.T.P. and M.M.), a Reginald A. Daly Postdoctoral Fellowship (J.T.P.), the Miller Institute for Basic Research in Science (J.X.M.), and NSERC (J.X.M.).

Author Contributions All authors contributed equally to this work.

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Correspondence to J. Taylor Perron.

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Supplementary information

Supplementary Information 1

This file contains Supplementary Discussion of the mechanics of post-Tharsis TPW on Mars, with reference to possible driving loads; Supplementary Figures S1-S2 with Legends and additional references. (PDF 275 kb)

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Perron, J., Mitrovica, J., Manga, M. et al. Evidence for an ancient martian ocean in the topography of deformed shorelines. Nature 447, 840–843 (2007).

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