The hope that signs of past ancient life may be found on the planet Mars took another small but significant step forward, following the release of new evidence that the Red Planet likely had a warm and very wet past, writes Dick Ahlstrom Science Editor
NASA's Opportunity rover, currently traversing a small crater on an area of Mars called the Meridiani Planum, has uncovered telltale signs of water in a rock outcrop that NASA officials have named "El Capitan". It lies close to the Martian equator where radiation from the sun would strike with its greatest impact.
"Opportunity has landed in an area of Mars where liquid water once drenched the surface," NASA's associate administrator, Mr Ed Weiler, told a news conference yesterday in Washington. "Moreover this area would have been good habitable environment," he added.
No signs of past or present life have been found on Mars - yet. Where there is water and warmth, however, there is usually life, a precept which certainly is true for Earth.
The rover, one of two NASA robots operating on the Martian surface, landed on January 24th. Since then it has been scrutinising finely layered bedrock in the crater's wall.
Scientists studying the pictures sent back by the rover suggested the layers could have been formed by wind, lava flows or water, but their current preferred option is water.
"We have concluded the rocks here were once soaked with liquid water," stated Dr Steve Squyres of Cornell University in New York state.
"We cannot tell you with certainty that these rocks were laid down in a lake, in a pool, in a sea," he said. The area "would have been suitable for life", he added.
"That doesn't mean life was there, but this was a habitable place on Mars at one period".
While the Spirit and Opportunity rovers can identify areas of interest on the surface, Earth-bound scientists will need rock and mineral samples to confirm the past existence of water.