Mars facts revealed by Nasa's Rovers

[steaner]

This artist's concept shows NASA's Spirit rover. For two years Nasa's Rovers have been exploring the surface of Mars, potentially paving the way for a human voyage to the Red Planet Photo: AFP

Image taken from the Mars Rover. For two years Nasa's Rovers have been exploring the surface of Mars, potentially paving the way for a human voyage to the Red Planet. Photo: AP

A promontory nicknamed "Cape Verde" can be seen jutting out from the walls of Victoria Crater in this approximate false-color picture taken by the panoramic camera on NASA's Mars Exploration Rover. Photo: AP

This false-color rendering shows the scene acquired by NASA's Spirit rover on martian day, or sol, 454 (April 13, 2005), using its panoramic camera. In the background is Clark Hill. Photo: AP

Taken by the Mars Exploration Rover Spirit's panoramic camera, this photograph shows a flaky rock called Mimi. Photo: AP

• Scraping soil revealed patches of ice that quickly evaporated.

• Soil in the planet's arctic circle contains calcium carbonate, which usually forms in the presence of water.

• A substance called perchlorate was found in soil. Some microbes on Earth use perchlorate as a source of energy

• It snows in the upper atmosphere but vaporises before reaching the ground.

• Life could exist in the frozen permafrost.

• Spirit and Opportunity, two rovers sent by NASA five years ago, have sent back 250,000 pictures from Mars and 36 gigabytes of scientific data.

• Sedimentary deposits may have formed from ancient lakes.

• Spirit landed in an old volcano with soil rich in sulphate and opal deposits.

• In 2006 the Mars Global Surveyor identified stains that appeared to be caused by gushing water on a gully wall.

• Five million years ago the Martian atmosphere could have been thick with ice clouds.