The Mars Science Laboratory. Credit: NASA/JPL-Caltech

When I hear about the search for alien life, it's hard not to think about all the science fiction movies with little green men and Earth-destroying spacecraft. But it's an idea that's far from science fiction for scientists at NASA Ames.

NASA is preparing to send their next rover to the surface of Mars, known as the Mars Science Laboratory. It follows the legacy of the twin rovers Spirit and Opportunity, who have survived far longer than NASA scientists expected. After four years, they're still sending data from the Martian surface. (For an update, check out this post from QUEST blogger Ben Burress).

The Mars Science Lab rover will have a few upgrades, though. It's much larger than Spirit and Opportunity and will be nuclear-powered — meaning no solar cells that are vulnerable to dust storms. It will also be carrying the most advanced lab equipment yet, some of which will look for organic matter on the surface. The goal to discover how habitable the surface could have been for life.

When it comes to what kind of life, it's microbial life that many scientists believe is the best case scenario. There have been a number of recent discoveries that are promising evidence that liquid water once existed on the surface. But if even the conditions were right for life then, they're certainly not right today. Thanks to a thin atmosphere, Mars is bombarded by solar radiation and conditions are dry and cold. Still, many scientists think there's a possibility that life could survive in the subsurface, where it's warmer and more sheltered.

The question most of us would ask, though, is: even if we found extraterrestrial life someday, how would we recognize it? NASA scientist Chris McKay explained his take to me. It turns out there are some basic things scientists believe they could look for. You can hear what he has to say in this audio clip:

McKay brought up another interesting point — we've already sent earthlings to Mars. The NASA rovers were built in clean rooms, but they're not completely sterile. Chances are there are microbes from Earth on Mars now, protected inside machinery we built. McKay believes this contamination is reversible, and there's already a policy in place to protect both Earth and Mars known as planetary protection.  You can hear McKay explain why it's so important in this clip.

No matter what the outcome of the Mars Science Lab mission, there's a lot more to discover about what Mars is like today and about its past.

Watch the Looking for Mars Life on Planet Earth report online.

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Artist concept of the Phoenix lander,
sleeping under the darkening polar skies of Martian autumn.

But that was last May, and Phoenix has operated near Mars' northern polar ice cap going on six months now! The mission has continued a couple months longer than originally planned, giving Phoenix more time to dig in the icy soil, bake scooped up samples to detect what chemicals sublimate, track the polar weather day and night, and look to the skies with its various instruments.

Phoenix sent back some very interesting news. Indeed, it had landed on what turned out to be dust-coated water ice; ice that contains chemicals like calcite and perchlorate– the former of which may indicate past liquid water on Mars, the latter of which, however, is generally toxic, and may complicate arguments for life, past or present, on Mars.

One of the more "fanciful" detections by Phoenix was falling snow: two or three miles above, Phoenix detected ice crystals falling from clouds– albeit flakes that never made it to the ground, instead evaporating like Earthly virga back into the atmosphere.

But Phoenix’s mission has a built-in conclusion (unlike the seemingly perpetual Energizer Bunnies exploring the Martian tropics, aka the Mars Exploration Rovers). Phoenix landed at 68 degrees north latitude– that’s equivalent on Earth to the north coast of Alaska, Norway, or south central Greenland– prior to Martian northern summer solstice (which was June 25). As with Earthly summertime, the polar days were unending, the Sun above the horizon 24 hours a day (yes, Mars' day is about 24 hours long, just as on Earth). This provided Phoenix with its electrical power, generated by photovoltaic panels.

But now the Sun is dipping below the horizon several hours a day as the Martian northern hemisphere slides in the direction of autumnal equinox (December 26, 2008), at which time the Sun will spend half the time below the horizon, the other half never rising very high. Already, Phoenix's solar panels are generating considerably less power than in the heyday of its mission. A dust storm, filling the air and blocking some of the already weak sunlight, has also cut available power to the lander for a time in October.

The diminishing conditions also caused Phoenix to put itself into an automatic "sleep" mode in late October, waking up for only a short time each day, when solar energy was at a peak. To give a flavor of the temperatures Phoenix is enduring, on Sol 151 (the 151^st Martian day since landing-October 27^th, Earth time), the daily high reached a balmy 50.8 degrees F-negative 50.8 that is! The night time low hit -128 degrees F… .

With every day possibly being the last we hear from Phoenix, scientists are collecting as much data as possible, mostly focusing on meteorological conditions. Reporting from the Martian polar ice cap, as the icy darkness of winter begins to settle in, this is Phoenix Lander, signing off….

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Forward camera view from Opportunity as the rover attempts to
climb up a slope toward the wall of Victoria Crater.
Photo by NASA/MER/Opportunity.

Four years after their planned three-month tour of duty began, NASA’s Mars Exploration Rovers (MER) Spirit and Opportunity roll doggedly on like a pair of aged, dusty desert prospectors looking for gold. In this case the "gold" is evidence for past water on Mars, and signs of that seem to abound.

What sparked this blog for me was the announcement of the plan to send Opportunity out of the depths of Victoria Crater, the half-mile impact crater that the rover has been exploring for almost a year now. Last September, when it was decided to send Opportunity into Victoria to get a close-up view of the sedimentary rock layers exposed in the crater walls, there was a lot of talk about this expedition possibly being the rover's last–it almost sounded like the robot was being sent into its own grave, its final resting place on Mars. After all, the rover had already operated ten times longer than what it was designed for!

What did Opportunity's year-long sojourn yield? By examining the multitude of exposed sedimentary layers, it is believed that those layers were probably originally laid down by wind (not a surprise on Mars, which even today is a world of wind-blown dust: dust devils, sand dunes, planet-wide dust storms). But there are also clues written in the rocks that the layers of sediment have been modified by the action of water.

One particular thing Opportunity has discovered are rock features dubbed "fins." These fins are raised edges around rock boundaries that are rich in the mineral hematite–a mineral that often forms in the presence of water. Opportunity found hematite on Mars early in its exploration, which supports the speculation that at least that rover’s region on Mars (Meridiani Planum) may have harbored at least shallow and intermittent bodies of water in the past.

The "fins" may have been formed when water dissolved away areas of sediment and then "filled in the holes" with deposited minerals–forming a kind of "fossil" of what was once an empty space.

When I lived in Northern Arizona, I remember driving across the plains east of Flagstaff and finding long, wide ridges of what looked like sandstone, snaking across the dusty desert like enormous gopher trails. I learned that these were the fossil remnants of what were stream beds: the streams formed deposits of sand and mud in their bed, which over time hardened into sandstone and mudstone. Later, the softer surrounding soils and sands eroded away, leaving the hardened stream beds as raised ridges of rock–dry evidence in a dry desert of past liquid water action. Though this is not the same process that formed the fins on Mars, it is analogous.

But now Opportunity's mission in Victoria Crater is done, and NASA is making plans to have the robot crawl back up the slope and exit the crater at the same place it entered last September. It will continue its mission by examining "cobbles"–small, loose stones on the surrounding planes, some of which were probably ejected by meteorite impacts in Mars' distant past.

Spirit, on the other side of the planet in Gusev Crater, is also still alive, and is making ready to do a bit more roving after a Martian winter of relative inactivity. With one of its six wheels no longer functioning, Spirit will limp along and continue prospecting–next stop: some white, silica-rich material that may have formed in hot water.

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