NASA scientists announced Wednesday that they have found evidence that water still flows on the surface of Mars in the form of sporadic gushers that increase the possibility that the Red Planet harbors some form of life.
Using images obtained by the Mars Global Surveyor spacecraft, the researchers concluded that changes in the shapes and sizes of gullies cut into the walls of two Martian craters were probably made by flowing water.
The team looked at two sets of images taken several years apart. In both cases, the second set of images revealed a light-colored substance several hundred yards long that had not been visible before, indicating that something had erupted from the ground and apparently sloshed toward the bottom of the basin.
“Today, we’re talking about liquid water being present on Mars right now,” said Ken Edgett, a staff scientist at Malin Space Science Systems in San Diego, which built the camera that took the pictures released Wednesday.
“You have all heard of a smoking gun,” he said. “This a squirting gun.”
The findings, to be published in the journal Science, bring scientists a step closer to answering the question, “Are we alone?” said David W. Beaty, acting chief scientist for the Mars program at the Jet Propulsion Laboratory in La Canada Flintridge, which operates the spacecraft.
But they also pose more issues for scientists. “The big questions are: How does this happen? And does it point to a habitat for life?” said Michael Meyer, lead scientist for NASA’s Mars Exploration Program.
The answers will not come soon. NASA’s two Mars rovers, Spirit and Opportunity, are on the surface but can’t investigate further because they are hundreds of miles from the gullies described Wednesday.
Still, the discovery, if further confirmed, would give the search for extraterrestrial life a new focus.
“Liquid water is one of only three things required by all life on Earth,” the Planetary Society, a Pasadena-based organization of space exploration advocates, said in a statement. “If there is liquid water on Mars, that makes it even more compelling to search for life on Mars.”
In another major finding, the science team said they found 20 new impact craters, ranging from 7 feet to 486 feet across, in other images from Global Surveyor. The scientists said that indicated that impacts from meteors could be a hazard for any human explorers on the planet.
The discoveries are something of a surprise, because Mars Global Surveyor, which was launched in 1996, is considered old technology.
For the last two years, NASA’s twin rovers have painstakingly examined the mineral content of rocks to try to uncover evidence of Mars’ watery past. The rovers found evidence that water covered large areas of Mars billions of years ago. NASA only recently announced that it had lost contact with the Global Surveyor because of a malfunction, making Wednesday’s announcement even sweeter. The craft’s original mission life was supposed to be two years.
Over its extended lifetime, it produced some 240,000 images. Finding the evidence of water required scrutinizing pictures of tens of thousands of gullies at hundreds of sites on the Martian surface.
According to Edgett, the discovery wasn’t so much a Eureka moment as a “Hey, what’s this?” moment.
Even after confirming their discovery in still more pictures, the science team was “kind of scared,” he said. “We thought, ‘Nah, this can’t be what it looks like.’ ”
This is not the San Diego team’s first Martian discovery. In 2000, they released results of their analysis of hundreds of gullies that they believed showed water had flowed “in the not-too-distant past.”
The latest findings came from images taken in 2004 and 2005. The team saw a white crust or patch on the surface in gullies in the Terra Sirenum and Centauri Montes regions of southern Mars that they hadn’t noticed before. Looking back to images taken in 1999 and 2001, they confirmed the deposits were new.
“The shapes of these deposits are what you would expect to see if the material were carried by flowing water,” said Michael C. Malin, president of Malin Space Science Systems. “They have finger-like branches at the downhill end and are easily diverted around small obstacles.”
Edgett said the amount of water appeared to be equivalent to five to 10 swimming pools in each case. The material flowed down a slope estimated at 20 to 30 degrees.
“It didn’t run out a great distance,” said Malin. He compared it to a “mud flow.”
Scientists are not sure what caused the substance to retain its whitish color on a planet where everything is coated with a layer of dust. “This is extremely unusual for Mars,” Malin said.
Malin said he believed it was some form of frost. The surface temperature on Mars ranges from minus 257 degrees Fahrenheit to minus 62 degrees. So water could not remain liquid for long.
If the water was contaminated with an acid, that would allow it to stay liquid at the surface, Malin said.
The alternative to frost is a salty crust. Both would be evidence of water flows. If it is a salty crust, the scientists said, it would have been produced by water concentrating salts in the Martian soil.
Malin believes the water is erupting from the “deep interior. When it reaches the surface, it creates a frozen dam. Eventually, the dam breaks and the water comes bursting out. It picks up debris and flows down the channel.”
The scientists speculated that a person observing the flows would see something like a flash flood -- a sudden eruption that washes down an arroyo, carrying soil with it. The surface of the flow would evaporate into a fog or mist of ice crystals.
In the past, some scientists have speculated that Martian ice could be frozen carbon dioxide. Edgett said it was difficult to see how CO2 could be sequestered underground in liquid form. “Most people lean toward [this being] water in some form,” he said.
To continue the search for water and life on Mars, Malin said he would direct a camera on the Mars Reconnaissance Orbiter, which began circling Mars this year to take over from Global Surveyor, to look at these sites and other gullies.