Life On Mars
When imagining locations where extraterrestrial life could potentially dwell, few places inspire the imagination like one of Earth's closest neighbors. For centuries, man has looked to Mars and imagined it as a home for other beings. Over the last fifty years, various missions to the red planet have sought to determine the probability of such an evolution. But how likely is life on Mars?
A habitable environment
When searching for life, most astrobiologists agree that water is key. All forms of terrestrial life require water, and while it is possible that life could evolve without the precious liquid, it is easier to search for conditions that are known to be optimal, rather than conditions we suppose could be." This raises a problem on Mars. The planet today is dry and barren, with most of its water locked up in the polar ice caps. The planet's thin atmosphere allows radiation from the sun to irradiate the surface of the planet, adding to the environment's challenges. Evidence for water first showed up in 2000, when images from NASA's Mars Global Surveyor found gullies that appeared to have formed from flowing water.
But Mars wasn't always a desolate wasteland. Scientists think that, in the past, water may have flowed across the surface in rivers and streams, and that vast oceans covered the planet. Over time, the water was lost into space, but early conditions on the wetter planet could have been right for life to evolve. One estimate suggests that an ancient ocean could have covered as much as 19 percent of the planet's surface, compared to the 17 percent covered by Earth's Atlantic Ocean. "With Mars losing that much water, the planet was very likely wet for a longer period of time than was previously thought, suggesting it might have been habitable for longer," said Michael Mumma, a senior scientist at Goddard, said in a statement. It's also possible that liquid water flows on a modern Mars, either on the surface or beneath. The debate continues today on whether features known as recurring slope lineae (RSLs) form from ongoing water flows or running sand. "We've thought of RSL as possible liquid water flows, but the slopes are more like what we expect for dry sand," Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona, said in a statement. "This new understanding of RSL supports other evidence that shows that Mars today is very dry. Water beneath the surface may be even better for life. Underground water could shield potential life from harsh radiation. There's evidence for an ice deposit the size of Lake Superior. "This deposit is probably more accessible than most water ice on Mars, because it is at a relatively low latitude and it lies in a flat, smooth area where landing a spacecraft would be easier than at some of the other areas with buried ice," researcher Jack Holt of the University of Texas said in a statement.
