Scientists find 'strong evidence' for ancient ocean on Mars
Sea would have existed billions of years ago, but probably did not harbour life
A EUROPEAN space probe has found strong evidence for an ocean that once existed on Mars. The Mars Express spacecraft used radar to detect material associated with a sea floor within the boundaries of previously identified shorelines. The European Space Agency has released a picture (above) of how the sea might have looked.
Scientists have theorised that two oceans existed in Mars's distant past: one four billion years ago, when the planet was warmer, and another three billion years ago, when ice under the planet's surface was melted by a large impact from space.
While tentative evidence for ancient shorelines has been proposed, the subject of ancient Martian oceans is still highly controversial.
The new evidence from the European Space Agency's Mars Express probe suggests the northern plains of the planet are covered in low-density material. Dr Jeremie Mouginot of the University of California, Irvine, said these are sedimentary deposits which may contain large quantities of ice.
"It is a strong new indication that there was once an ocean here," he added.
Wlodek Kofman, the leader of the radar team at the Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), said that there is evidence for sedimentary material and ice throughout the first 60-80m under the Martian surface.
This is consistent with the three-billion-year-old ocean, but Dr Mouginot believes the water could only have existed for less than a million years before freezing once more underground or evaporating into the atmosphere.
"I don't think it could have stayed as an ocean long enough for life to form," he said.
If life existed on Mars, it is far more likely to have done so when liquid water existed for longer periods, perhaps in the four-billion-year-old ocean.
However, the evidence for ancient Martian oceans is now piling up. "Previous Mars Express results about water on Mars came from the study of images and mineralogical data, as well as atmospheric measurements," says the ESA's Olivier Witasse. "Now we have the view from the subsurface radar.
"This adds new pieces of information to the puzzle, but the question remains: where did all the water go?" ·
