March 25, 2009
Scientists Discuss Evidence Of Liquid Water on Mars
Researchers at the 40th Lunar and Planetary Science Conference in the Woodlands, Texas have been discussing the possibility that water may actually exist on Mars.
It was previously assumed that water existed on the Red Planet only in the form of ice or vapor due to the low temperatures and atmospheric pressure.
However, the recent discovery by NASA's Phoenix probe showing that perchlorate salts exist within the soil of Mars adds credence to the idea of liquid water on the planet.
Some researchers believe that perchlorate salts, which can keep liquid at temperatures of minus 70C, may be mixed with ice to form pools of liquid water on the planet.
"I do think those pools might exist. But there's still more to know about the properties of these perchlorate solutions, such as what their vapor pressure is," Dr Mike Hecht, from Nasa's Jet Propulsion Laboratory (JPL) in Pasadena, California, told BBC News.
"Here are all these perchlorate salts right under them, by a few centimeters, is a slab of [water ice]. It doesn't take much of a stretch of the imagination to say that those two materials will interact."
"And once you get dampness, the perchlorate is very soluble and it will become mobile," he added.
In order for these pools to form on the surface of Mars, it would require a specific balance of perchlorate salts within the soil, Hecht said.
"In this case we have very little perchlorate and vast slabs of ice, so I can imagine we have an excess of water. This means you would form a pool of low temperature brine if the two ever interacted."
Some researchers say the concentrations of perchlorate salts discovered by the Phoenix lander were one small piece of the entire soil composition.
Professor Peter Smith, of the University of Arizona, told the conference that several things point to the existence of water on the Red Planet, including the presence of aqueous minerals, cloddy, cemented soil and the discovery that some of the ice was "segregated", showing signs of melting.
"It's probable that in a warmer, wetter climate, as when the obliquity (the extent to which Mars is tilted on its axis) changes, this could be a place where liquid water is found. That doesn't mean it's a lake. It just means that the soil is wet," said Smith.
Calcium carbonate, the main component in limescale on Earth, was also found within the Martian soil at levels of 3-5 percent at the probe's landing site.
Smith told BBC the calcium carbonate likely formed as carbon dioxide dissolved into liquid water, forming a week acid that leached calcium from the soil.
In yet another piece of evidence, Dr Nilton Renno, from the University of Michigan, presented images that show droplets of liquid water on the leg of the Phoenix probe.
In a new paper released at this month's meeting, 22 mission members say those tiny droplets give credence to the existence of water on the Red Planet.
"The (spheroids) move, drip and merge," said Renno.
"It's highly unlikely that that's the explanation," Mike Hecht told the AP earlier this month.
"It's just water vapor moving around. It's an ordinary, unexciting explanation."
"The photographs are clipped from the corners of relatively low resolution images, so the number of pixels across those droplets is very small. Trying to ascribe shapes to them, to say they are spheres - which are characteristic of liquid - is going beyond the quality of the images," he said.
Phoenix launched from Cape Canaveral Air Force Station in August with the purpose of seeking out environments that could be habitable for life forms.
Phoenix Mission Control reported loss of contact with the lander on November 10, 2008.
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