Mars Express Orbiter Finds Possible Sediments of Ancient Martian Ocean Floor

Posted on February 9, 2012

The MARSIS radar instrument on board ESA's Mars Express orbiter has discovered a subsurface blanket of low density material around the north polar cap. The discovery supports theories that Mars once had a massive ocean covering its northern lowlands.

Mars has enormous outflow channels (now dry) that astronomers believe were carved out by raging torrents of sediment-laden water. The flash floods appear to have occurred between 2 billion and 4 billion years ago. Astronomers think the outflow channels fed a shallow Martian ocean that once covered over 30% of the planet's surface.

Analysis of new MARSIS radar data revealed new evidence of an ancient northern ocean on Mars. The radar probed the subsurface of Mars, which revealed contrasts in dielectric constant caused by the density of the materials and the amount of ice in the ground. A high dielectric value indicates the presence of dense material, whereas a low value shows a fairly low density or high content of ice. A paper published in Geophysical Research Letters argues that the data points toward an ancient ocean. There is a huge region of low dielectric values in the northern plains of Mars, which extends toward lower latitudes in the regions of Amazonis Planitia, Chryse Planitia and Utopia Planitia.

Wlodek Kofman, co-author of the paper and a co-investigator on the MARSIS instrument team, says, "The presence of low density material, potentially mixed with ice, suggests that we are observing sedimentary material, tens of metres thick, that was eroded by fast-flowing water and carried downstream before being deposited in an ocean."

Jeremie Mouginot, Antoine Pommerol, Pierre Beck, Wlodek Kofman, and Stephen M. Clifford, Geophysical Research Letters, Vol. 39, L02202, 2012. DOI: 10.1029/2011GL050286

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