Pictures from Nasa’s roving Mars buggy have astonished scientists by indicating that it may have landed in mud.
Strange marks near the Spirit rover’s landing site suggest that against all the odds there be might liquid water on or just beneath the surface of Mars.
The water would have to be very salty to avoid freezing or evaporating in the harsh Martian conditions.
If the scientists’ suspicions are confirmed it would be the clearest sign yet that lakes and oceans once existed on Mars, and greatly increase the chances of life.
The presence of water in the Martian soil could even mean that the Viking Mars landers really did detect life on the planet in 1976.
Positive results from the Viking experiments were dismissed when it was realised they could have been produced by an inorganic chemical process. But mud on Mars would rule out this explanation for the strange findings.
The mystery stems from a small disturbed patch of ground very close to the lander, New Scientist reported today.
Dubbed the “magic carpet”, it was made by the lander’s airbags scraping across the soil.
But its appearance has taken scientists completely by surprise. Instead of breaking or cracking, as dry soil would be expected to do, the surface seems to have flowed and folded as if wet.
Science team leader Steven Squyres said: “It looks like mud, but it can’t be mud.”
Pure water cannot exist at the low temperatures and pressures found on Mars – it would either freeze or evaporate away.
But scientists say that is not true of brine. If the water contained enough salt, it could be stable.