12-07-2006, 01:20 AM
by Fanny Carrier
NASA experts said they have detected evidence that liquid water existed on the surface of Mars in recent years, giving weight to hopes that signs of life on the Red Planet could still be found.
An orbiter going around Mars has photographed gullies which indicated that water had flowed there in the past decade.
"These observations give the strongest evidence to date that water still flows occasionally on the surface of Mars," said Michael Mayer, head of NASA's Washington-based Mars Exploration Program.
"We had evidence of ancient water. But today we're talking about liquid water that is present right now on Mars," said Kenneth Edgett, a scientist at Malin Space Science Systems in California who took part in the research.
The finger-shaped gullies are each several hundred meters (yards) long. They are "what you would expect to see if the material were carried by flowing water," according to Michael Malin, the lead researcher in the study of pictures taken by the US National Aeronautics and Space Administration's Mars Global Surveyor in 2004 and 2005.
Stargazers have long wondered whether there has been life on Mars, and the presence of liquid water is considered essential for it.
The surface of Mars is too cold for liquid water to exist, but scientists believe underground water filtered to the surface carrying debris downslope long enough to form the gullies before it froze.
The light-colored deposits in the gullies, they said, could be from surface frost replenished by ice from inside the deposit.
A study of the evidence of water on Mars is to be published in the December 8 edition of Science magazine.
The Mars Global Surveyor orbiter has taken 240,000 pictures of the surface of Mars since 1997. The space agency has not been able to contact the orbiter since November, however.
The pictures included thousands of small gullies. But in 2005 the orbiter detected two new gullies that had not existed when the region had previously been photographed.
Previous research has shown that Mars was once warm and humid and that there is still some ice underground at the polar extremes.
Scientists said the new images did not directly show water but that they indicated there had been a flow of enough material down the new gullies, carried by running water, to fill between five and 10 swimming pools.
They said in the Science article that their research had concluded "it is possible for liquid water to exist beneath the ground and come to the surface under modern Martian conditions."
Some scientists have said the gullies could have been created by liquid carbon dioxide (CO2) coming to the surface. But the NASA experts said this was unlikely because of the difficulty in burying "volatile" CO2.
NASA experts and others want to carry out new experiments to advance the hunt for water and life on the planet, but they warned Wednesday that the number of asteroids that have collided with Mars would be a major obstacle to a manned mission to the planet.
The MGS orbiter had detected many new craters formed from the impact with asteroids in recent years.
NASA said there had been about a dozen collisions a year, including some which had caused huge explosions and left craters the size of a football stadium.
http://news.yahoo.com/s/afp/usspacenasamars
NASA experts said they have detected evidence that liquid water existed on the surface of Mars in recent years, giving weight to hopes that signs of life on the Red Planet could still be found.
An orbiter going around Mars has photographed gullies which indicated that water had flowed there in the past decade.
"These observations give the strongest evidence to date that water still flows occasionally on the surface of Mars," said Michael Mayer, head of NASA's Washington-based Mars Exploration Program.
"We had evidence of ancient water. But today we're talking about liquid water that is present right now on Mars," said Kenneth Edgett, a scientist at Malin Space Science Systems in California who took part in the research.
The finger-shaped gullies are each several hundred meters (yards) long. They are "what you would expect to see if the material were carried by flowing water," according to Michael Malin, the lead researcher in the study of pictures taken by the US National Aeronautics and Space Administration's Mars Global Surveyor in 2004 and 2005.
Stargazers have long wondered whether there has been life on Mars, and the presence of liquid water is considered essential for it.
The surface of Mars is too cold for liquid water to exist, but scientists believe underground water filtered to the surface carrying debris downslope long enough to form the gullies before it froze.
The light-colored deposits in the gullies, they said, could be from surface frost replenished by ice from inside the deposit.
A study of the evidence of water on Mars is to be published in the December 8 edition of Science magazine.
The Mars Global Surveyor orbiter has taken 240,000 pictures of the surface of Mars since 1997. The space agency has not been able to contact the orbiter since November, however.
The pictures included thousands of small gullies. But in 2005 the orbiter detected two new gullies that had not existed when the region had previously been photographed.
Previous research has shown that Mars was once warm and humid and that there is still some ice underground at the polar extremes.
Scientists said the new images did not directly show water but that they indicated there had been a flow of enough material down the new gullies, carried by running water, to fill between five and 10 swimming pools.
They said in the Science article that their research had concluded "it is possible for liquid water to exist beneath the ground and come to the surface under modern Martian conditions."
Some scientists have said the gullies could have been created by liquid carbon dioxide (CO2) coming to the surface. But the NASA experts said this was unlikely because of the difficulty in burying "volatile" CO2.
NASA experts and others want to carry out new experiments to advance the hunt for water and life on the planet, but they warned Wednesday that the number of asteroids that have collided with Mars would be a major obstacle to a manned mission to the planet.
The MGS orbiter had detected many new craters formed from the impact with asteroids in recent years.
NASA said there had been about a dozen collisions a year, including some which had caused huge explosions and left craters the size of a football stadium.
http://news.yahoo.com/s/afp/usspacenasamars