NASA is looking at extending its Mars rover excursions after finding what it believes is evidence of past liquid water activity on the planet. The space agency says the appearance and composition of a rock outcrop examined by the Opportunity rover provides "strong evidence" that the Meridiani Planum was once "drenched" with water.

In a bid to confirm the past presence of water, and to measure its extent, NASA wants to examine other rocks in the shallow "Laguina Hollow" crater where Opportunity is located, then send the rover on a 740m (2,400ft) trek across the plain to a 160m-wide, 30m-deep crater dubbed "Endurance" - an operation that is expected to take "several weeks". This crater is ringed in bright rock that NASA hopes will provide corroborating evidence of water activity.

Evidence that the bedrock examined by Opportunity was once wet includes its high concentration of sulphate salts, which usually form in water; the presence of voids, possibly left by the dissolving of crystals; and round particles, or sperules, possibly formed by the accumulation of minerals inside a water-soaked rock. What is not clear is whether the rocks were soaked or immersed in water.

While convinced it has found evidence that liquid water existed on the surface of Mars, NASA cannot say whether water once flowed freely across the surface of Meridiani Planum. "Were the layered rocks laid down in liquid water? We don't have the answer. Were the rocks acted on or altered by liquid water? The answer we believe is definitely yes," says principal investigator Steve Squyres.

NASA plans to direct Opportunity towards a nearby rock that appears to show signs of crossbedding, a distinctive pattern that can result from the action of flowing water, but also from the flow of air or volcanic ash. To confirm the presence of liquid water on Mars, and determine how long ago it existed, the agency believes a sample return mission will be necessary.


Source: Flight International