1.2 MB full resolution version

MOLA topography. (a) MOLA profile 10190 near the Utopia impact basin. (b) MOLA profile 10929 near the Alba Alba Patera volcano. In (a) and (b) terraces and ridges are marked by horizontal and vertical lines, respectively. Vertical exaggeration is 400:1. (c) Viking photomosaic near the Utopia impact basin, Mercator projection. (d) Shaded relief map generated from MOLA digital terrain model of the same region and using the same projection as in (c). Many ridges are visible in the MOLA image that are not evident in the Viking image. (Image Credit: MOLA Science Team)

MOLA summer intern Paul Withers, a graduate student at the University of Arizona, teamed up with Greg Neumann of the MOLA team to study the northern plains of Mars. Before MOLA, it was thought that the plains were flat and featureless, reflecting a widespread deposition of volcanic and sedimentary material. But high-resolution shaded relief maps from MOLA, such as the one shown in the figure above, showed that the plains display many subtle features, including pervasive wrinkle ridges. Wrinkle ridges are tectonic features formed due to compressional stresses associated with loading of the Martian surface due to the formation of the Tharsis rise, and possibly also due to dynamical effects in the interior of Mars.

Withers and Neumann noticed that certain features that were previously interpreted as shore lines looked just like the wrinkle ridges, and thus were not likely formed in association with an ocean. The result of this study arguably weakens one line of evidence for the existence of an ocean in the northern plains of Mars during the middle part of Martian history (the Hesperian epoch). Scientists are divided over whether an ocean existed during this period of time on Mars, but most believe that an ocean or many seas was/were likely earlier in Martian history (the Noachian epoch).

Withers, P. and G.A. Neumann, Enigmatic ridges on the plains of Mars, Nature, 410, 652, 2001.

Download a PDF version of the paper
Read the press release