Mars holds vast stores of water ice right near the surface and away from the permanently frozen south polar ice cap, scientists say. This means it?s possible that life may have once existed on Mars or could still be there.
?There?s a lot of ice on Mars,? says William Boynton, who made the discovery. ?We really have a whopping large signal.? What he?s spotted is hydrogen, which is one of the components of water. Boynton and his colleagues believe there is actual water ice at the surface, as well as a few feet down.
Scientists already knew there was water locked up in the northern ice cap, along with carbon dioxide ice. But life needs liquid water, so finding water ice nearer the equator greatly increases the chances that the ice might melt seasonally, meaning there could be life on Mars.
The new discovery comes from images sent to Earth by NASA?s Mars Odyssey spacecraft. Odyssey?s mission officially began February 19, but some data and images were sent back to Earth when the craft first went into orbit around Mars on October 23.?For the first time we're seeing elementary chemicals on the surface of Mars,? says Stephen Saunders, an Odyssey project scientist. ?Our Odyssey has just begun.?
Boynton believes the northern hemisphere may contain similar amounts of water ice, but can?t tell until the Mars summer, when the large polar cap recedes. The polar cap is mostly made up of carbon dioxide ice, which cover ups what?s underneath.
Scientists have long suspected that water once flowed on Mars, when the planet was warmer. Evidence of this has increased in recent years, thanks mostly to the Mars Global Surveyor, another NASA spacecraft that is orbiting the planet.
As Mars cooled millions or billions of years ago, the surface water froze or evaporated into space through a thinning atmosphere. However, some water may have remained frozen in the soil or trapped in underground reservoirs, and heat from inside the planet may still keep some of it in liquid form. The underground water ice may also melt periodically.
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The most recent floods on Mars took place in the recent geologic past, not billions of years ago as previously estimated. A huge amount of water gushed over the surface of the planet about 10 million years ago, according to planetary geologists investigating images from the Mars Global Surveyor. The liquid water came from fissures near the Martian equator, the same cracks that produced huge amounts of lava.
?This is a completely different water release mechanism than previously studied on Mars,? says Devon Burr of the University of Arizona. Comparable deluges on Earth have left behind landforms that are similar to the ones Burr and his colleague Susan Sakimoto of NASA found on Mars.
In the 1970s, satellite pictures from the Viking spacecraft convinced many scientists that colossal water floods carved great gullies on Mars, but those floods were thought to have taken place more than 2 billion years in the past. ?Athabasca Valles [a valley system just north of the Mars equator] is an almost new component in the Martian hydrological cycle,? Burr says. ?The water here gushed from volcano-tectonic fissures. While the fissures themselves may be older, the latest eruption of the water was probably only about 10 million years ago.? Geothermal sites on Mars could still be active, providing the cold, dry planet with periodic doses of heat and water?and life.
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Richard Greenberg of the University of Arizona says a combination of physical conditions on Europa, one of the moons of Jupiter, might not only make life possible but also encourage it to evolve.
Europa is an icy world that appears to be pocked with strange streaks of color and is continuously contorted by the powerful pull of Jupiter, the largest planet in our solar system. Greenburg believes those tidal forces could warm a subsurface ocean and push liquid pockets to the surface on occasion, encouraging primitive life forms to evolve.
?The implication is that these settings would actually be hospitable to life,? says Greenberg, who works on the NASA Galileo probe, which has orbited Jupiter since 1997. Galileo?s photos and scientific measurements provide strong evidence that Europa has the largest salty ocean in our solar system underneath its frozen exterior.
The Galileo findings ?opened the door to speculation about life,? says Greenberg. As early as 1996, reports were being issued about new data that indicated ?a primitive life form? on Europa.
Besides water, ideal conditions for life include heat. The gravitational tides put into motion on Europa by Jupiter periodically stretch the icy surface as high as 1,600 feet above the normal sea level. ?Everything on and under the surface is driven by the tides,? Greenberg says. ?The ocean is interacting with the surface. There is a possible biosphere that extends from way below the surface to just above the crust.? The friction from this tidal pull could generate enough heat to melt the ice on the surface. Close-up photos of the surface indicate that exterior cracks frequently thaw and refreeze.
Greenburg speculates that organisms on Europa would mimic microbial life forms in oceans on Earth. But Norman Pace, of the University of Colorado, says the prospects of finding life on Europa are slim and believes that the chances of finding life are much better outside than inside our solar system. ?The basic theme here is that if you look at what is required for life, it really is a narrow window,? Pace says. ?Our solar system outside Earth doesn?t seem too promising to sustain life. But we don?t know what kind of extreme conditions conducive to life may be found elsewhere in the universe.?
To see images of what might be life on Mars, read ?Dark Matter, Missing Planets & New Comets? by Dr. Tom van Flandern,click here.
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