Washington, Nov 20 : As NASA selects a landing site for its next Mars mission called the ‘Mars Science Laboratory’, four intriguing places on the Red Planet have made it to the final round.

The sites, alphabetically, are: Eberswalde, where an ancient river deposited a delta in a possible lake; Gale, with a mountain of stacked layers including clays and sulfates; Holden, a crater containing alluvial fans, flood deposits, possible lake beds and clay-rich deposits; and Mawrth, which shows exposed layers containing at least two types of clay.

“All four of these sites would be great places to use our roving laboratory to study the processes and history of early Martian environments and whether any of these environments were capable of supporting microbial life and its preservation as biosignatures,” said John Grotzinger of the California Institute of Technology, Pasadena.

The agency had a wider range of possible landing sites to choose from than for any previous mission, thanks to the Mars Science Laboratory’s advanced technologies, and the highly capable orbiters helping this mission identify scientifically compelling places to explore.

The mission’s capabilities for landing more precisely than ever before and for generating electricity without reliance on sunshine have made landing sites eligible that would not have been acceptable for past Mars missions.

During the past two years, multiple observations of dozens of candidate sites by NASA’s Mars Reconnaissance Orbiter have augmented data from earlier orbiters for evaluating sites’ scientific attractions and engineering risks.

JPL is assembling and testing the Mars Science Laboratory spacecraft for launch in fall 2009.

Paring the landing-site list to four finalists allows the team to focus further on evaluating the sites and planning the navigation.

The mission plan calls for the rover to spend a full Mars year (23 months) examining the environment with a diverse payload of tools.

After evaluating additional Mars orbiter observations of the four sites, NASA will hold a fourth science workshop about the candidates in the spring and plans to choose a final site next summer.

Three previous landing-site science workshops for Mars Science Laboratory, in 2006, 2007 and two months ago, drew participation of more than 100 Mars scientists and presentations about more than 30 sites.

The four sites rated highest by participants in the latest workshop were the same ones chosen by mission leaders after a subsequent round of safety evaluations and analysis of terrain for rover driving. (ANI)