A Martian mineral deposit 300 miles wide has led to speculation that there was water on Mars long enough for life to form.

Crater found in volcanic region of Mars

The findings, from the National Aeronautics and Space Administration's Mars global surveyor spacecraft, were presented in Boston before the American Geophysical Union.

Professor Phil Christensen of Arizona State University said that the deposit "is really the first evidence we have that hot water was around long enough for a geological period of time so that potentially life could have had an opportunity to form."

The deposit, hematite, is an iron oxide mineral that forms by a variety of ways that often involve water.

The coarse-grained hematite spotted on Mars occurs on this planet around volcanic regions on this planet.

Scientists working on the Mars Global Surveyor Mission said the find is evidence that a large scale hydrothermal system operated beneath the Martian surface.

Professor Christensen said: "If you want to find out about possible life on Mars, the deposit is a good place to start.

"You've got water, you've got heat, got energy. It's a good place if you want to have life."

Mineral deposit 300 miles wide

Dr David Smith of Nasa's Goddard Space Flight Centre said a laser altimeter aboard the satellite orbiting above Mars had mapped the topography and in April discovered new information about the planet's north polar cap and its surrounding features, including dune fields that share similar properties to North Africa.

The instrument also revealed the presence of high altitude clouds above the polar cap.

A composite photograph of a crater 25 miles wide and one mile deep about 3,600 miles south of the Martian equator was also displayed.

The deep, dark area near the middle of the crater appeared to be a frozen pond and there was evidence of seepage as well, Smith said.

"It's like a dry lake," he said.