Mars Images Have Experts Gushing
Violent, geyser-like eruptions of liquid water appear to have broken through the Martian surface in hundreds of places in the coldest parts of the planet, boosting hopes of finding life on Mars, according to ebullient scientists who presented details of their still controversial findings Thursday.
“I think it’s the smoking gun that says there’s liquid water and Mars meets all the requirements for life,” said Bruce Jakosky, who heads the Astrobiology Institute at the University of Colorado.
New images from the Mars Global Surveyor show hundreds of sites where steep gullies and channels are carved into the planet’s surface. The perplexing gullies appear in pits, valleys and craters clustered in five main locations on the planet and are more common in the southern hemisphere.
The features appear to have been recently carved by flowing water. While they could be millions of years old, they also “could have formed yesterday,” said Michael C. Malin, who heads San Diego-based Malin Space Science Systems, a subcontractor for NASA in charge of the camera mounted on the Jet Propulsion Laboratory spacecraft.
The finding rendered normally conservative scientists giddy with excitement about prospects for additional discoveries on Mars and left NASA administrators pleased to have some good news to report after the loss of two Mars spacecraft last year.
“This is a fun press conference,” Edward J. Weiler, NASA’s associate administrator for space science, said in Washington on Thursday. “Unlike some I’ve been having lately.”
Scientists are still struggling to understand how water in liquid form could reach the surface and persist long enough to gouge out the features captured in the images.
It was thought that the frigid planet would support only ice--not liquid water--near its surface. In the thin Martian atmosphere, water is believed to immediately evaporate. Scientists believe that vast oceans once covered parts of the planet but evaporated or froze billions of years ago.
“We have a problem,” said Michael Carr, a planetary scientist with the U.S. Geological Survey who has studied Mars for 30 years and was not involved in the research. “We have conditions which seem to forbid there being liquid water close to the surface.”
The new findings would suggest otherwise. Though he called for caution in making too much of photographic evidence, Carr did remark that the channels look “just like features you see flying over the West” that were carved by water.
Also perplexing is the fact that the gullies appear in places where scientists would least expect to find water--the coldest spots in the planet’s coldest regions. The gullies and trenches are sprinkled near polar latitudes, where temperatures are routinely more than 100 degrees below zero Fahrenheit. Further, they are found within craters on the slopes that receive the least amount of warming sunlight.
“We were quite surprised and confused,” Malin said of the images.
He and fellow planetary scientist Kenneth S. Edgett theorize that liquid water, possibly warmed by some source of geothermal energy within the planet, could travel to the surface in channels made of permeable rock.
At the surface most water would evaporate, but some could freeze and form an ice dam. Pressure building behind the ice dam could lead to a massive release of water--enough to fill several swimming pools--that would send a flash flood down a gully and carve out channels.
Malin and Edgett described such a process as a violent, geyser-like eruption.
Any water involved would probably be very salty, because salty water can remain liquid at colder temperatures.
Edgett, who had not believed he would find signs of water on the planet, said, “I was dragged kicking and screaming to this conclusion” by the evidence in the photographs.
The gullies are recent, he said, because they are not pockmarked by craters, as older parts of the planet are. In some places the deep trenches cut through youthful geological features such as sand dunes. And the gullies are not covered by the ubiquitous Martian dust that quickly coats rocky features and spacecraft on the planet’s surface.
Alternative Theory Posed
Although the water theory is “very compelling,” Carr said it is possible that the features were not caused by liquid water but by dry avalanches or rock flows lubricated by carbon dioxide emissions from the planet.
Other scientists were excited by the finding but perplexed.
“It’s kind of like we have a crime scene and a really strong suspect, but the suspect has a good alibi. The alibi is that physics doesn’t allow liquid water on Mars,” said John Callas, a research scientist on the Mars exploration team at JPL.
Mars scientists are obsessed with finding liquid water because it is a major prerequisite for life on Earth and is thought to be a requirement for extraterrestrial life.
Although the new finding does not suggest vast pools of water at the surface, it does seem to indicate that there is enough water near the surface to support some forms of life, Jakosky said.
On Earth, some life forms can survive repeated freezing and thawing and can exist within ice, he said. The discovery of so-called “extremophiles” has scientists moving away from the “Goldilocks theory of biology,” in which conditions must be “just right” for life to exist, said NASA’s Weiler.
Any life found on Mars is likely to be microbial, said Weiler, who also cautioned that early reports of the finding were exaggerated. “They have not found lakes and rivers flowing on Mars. They have not found hot springs on Mars. They have certainly not found a hot tub with Martians swimming in it,” he said.
Still, excitement at the finding led to immediate speculation over whether NASA would redirect or speed up plans to explore Mars and whether the discovery would justify a manned mission to the Red Planet. Water on Mars, if it is potable or can be purified, would cut down on the supplies people would need to carry with them to the planet. It could also theoretically be broken down into breathable oxygen, though such ideas remain speculative.
Weiler immediately ruled out any manned missions in the near future, saying decades of robotic exploration would be required first. A new orbiter is scheduled to be launched to Mars next April.
NASA--stung by the failure of the recent Mars missions--is deciding whether to send an orbiter or a lander to the planet in 2003. The agency will continue, Weiler said, with its “follow the water” approach.
An orbiter mission with a higher-resolution camera could provide more conclusive photos of the gullies and ravines and could search for mineral traces left by water flows, said Richard W. Zurek, a scientist at JPL now working on plans for that orbiter.
Scientists are also interested in sending a lander with a robotic rover that could drill for Martian water at one of the sites. The prospect had not been seriously considered until now because it was thought that water would be more than a mile below the surface.
The new finding was originally scheduled for publication June 30 in the journal Science. The announcement was made a week early because preliminary reports about the finding were posted on Web sites and then widely reported by newspapers and other media outlets.
(BEGIN TEXT OF INFOBOX / INFOGRAPHIC)
New Theory
A camera on board the Mars Global Surveyor has photographed numerous gullies and trenches running down the slopes of craters. The channels appear to have been carved by water.
*
Sources: Mike Malin and Ken Edgett, Malin Space Science Systems/JPL/NASA
