Images taken from an orbiting spacecraft have revealed two fresh features in the Martian landscape that scientists think were been formed by brief torrents of water as recently as 2001.

The remarkable observations show for the first time that modern Mars may not be as dry and barren as is usually assumed, and thus have important implications for its potential as a hospitable place for life.

Wherever liquid water is found on Earth, there is also life, and most scientists consider its presence a prerequisite for the existence of primitive extraterrestrial organisms.

If it sometimes exists on Mars today, it raises the very real prospect that life may not only have evolved there in the past, but could still survive there in modern times.

Water ice has previously been detected at the Martian poles, and many of the planet’s features are known to have been formed by water in the distant past, but there have been few firm indications that it is present today in liquid form.

That has changed with the new images from Nasa’s Mars Global Surveyor spacecraft. Between 1999 and last year, it took pictures of thousands of gullies, which have now been examined for evidence of significant change.

Professor Philip Christensen of Arizona State University, a senior scientist with the Mars Global Surveyor team, said: "Five years ago, we were talking about water on Mars five million years ago. Today we can honestly talk about water on Mars today. That revolution in our thinking has really changed how we think about Mars and how we should think about exploring Mars."

At two sites — the Terra Sirenum crater and an unnamed second crater in the Centauri Montes region — channels were seen in later images containing fresh, pale-coloured deposits that appear to have been left by flowing water.

At Terra Sirenum, the image changed dramatically between passes made in December 2001 and April 2005, and at Centauri Montes the changes happened between August 1999 and February 2004.

The character of the deposits left by whatever cascaded briefly down these slopes, particularly the way it has flowed around solid obstacles, points firmly towards water rather than dust as the source of the new features.

“The new gully deposits, formed since August 1999, are light toned and exhibit attributes expected from emplacement aided by a fluid with the properties of liquid water,” said Mike Malin, chief scientist for the camera which took the images.

“The observations suggest that liquid water flowed on Mars during the past decade.”

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