Did Mars once have oceans? New evidence says yes.

Sedimentary deposits suggest that Mars was once covered with seas and lakes of liquid water some 4.5 billion and 3.5 billion years ago.

This 2008 photo shows the Phoenix Mars Lander's solar panel and the lander's Robotic Arm with a soil sample in the scoop on Mars. A new study suggests that the red planet was once covered with lakes and seas of liquid water.

Planet-mappers have uncovered powerful new evidence that Mars was once covered with seas and lakes of water. Researchers combined measurements from instruments on orbiting NASA spaceprobes to plot the Red Planet’s terrain in detail.

Their results point to the existence of a series of layers of sediment left by large areas of liquid water in a region called Hellas Planitia in Mars’s southern hemisphere.

The investigators interpreted fine-layered outcrops around Hellas’s eastern rim as sedimentary deposits. They say they were produced by the erosion of rock in the highland regions which were then carried into a basin-wide body of water.

IN PICTURES: Mars Spirit rover

Announcing the findings, Dr Leslie Bleamaster, of the Planetary Science Institute in Tucson, Arizona, said the lakes or seas existed between 4.5 and 3.5 billion years ago. Conditions then may have been more favourable for the existence of life, many scientists believe.

The Hellas basin, more than 2,000 km wide and 8 km deep, was produced by a massive impact early in Mars’s history. It is the largest impact site on the planet.

Dr Bleamaster said: “Our mapping and evaluation of landforms and materials of the Hellas region from the basin rim to floor provides further insight into Martian climate regimes and into the abundance, distribution, and flux of volatiles through history.”

In planetary science, volatiles is the name given to water and chemical elements with a low boiling point that are found at a planet’s surface or in its atmosphere and crust. Evidence has previously been found for an ocean near the martian north pole.

The NASA rovers Spirit and Opportunity have also found deposits at the surface that must have been left by water. Spirit’s tracks churned up bright silica. More recently, the Phoenix lander photographed water ice beneath the craft and in a trench it dug.

Data for the geologic mapping project was obtained from scanning instruments aboard the Viking Orbiter, Mars Odyssey and Mars Orbiter spacecraft. The new map and accompanying map pamphlet may be found here.

• Discover space for yourself and do fun science with a telescope. Here is Skymania’s advice on how to choose a telescope. We also have a guide to the different types of telescope available. Check out our monthly sky guide too!

Paul Sutherland blogs at Skymania News

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IN PICTURES: Mars Spirit rover

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