The rovers are identical to each other The soil on Mars could be identical almost everywhere showing that, like on the Moon, its composition is unrelated to the immediately underlying rocks. Study by the US rovers which touched down in January would suggest the soil has been mixed up by wind and impacts. Its make-up is roughly the same as that found at the landing sites of the two Viking landers in 1976 and the Mars Pathfinder mission in 1997. Nasa revealed the soil data at the 2004 Lunar and Planetary Science Conference. The first results from the Spirit...