Scientists have long known that Mars' polar regions contain huge reservoirs of frozen water, but today's findings on the depth and purity of that ice have raised the regions' profile as a place to search for evidence of life - as well as a destination for future human missions.
The splashiest fact coming out from today's research, published online by the journal Science, is that there's enough water in the south polar region's layered deposits to cover the entire Red Planet in a liquid layer about 36 feet (11 meters) deep.
That may sound like a lot - but the lead researcher behind the study, Jeffrey Plaut of NASA's Jet Propulsion Laboratory, told me today that Mars must have had lots more when it was a warmer, wetter planet, perhaps billions of years ago. That conclusion is based on the erosional patterns seen on Mars today.
"You probably need 10 times as much water as we've identified in order to do all that erosion," Plaut said.
What's more surprising about today's result, at least for the experts, is the purity of the ice. Radar readings from the MARSIS instrument on Europe's Mars Express showed that the ice was at least 90 percent pure water. Those ice layers go down as far as 2.3 miles (3.7 kilometers) beneath the surface - and are topped by a mixture of ice and dust that may be only a yard (meter) or so thick.
All this makes the little-explored polar deposits more tantalizing for Mars mission planners, Plaut said. NASA's Mars Polar Lander would have touched down amid such deposits if it hadn't crashed back in 1999. The Mars Phoenix lander, due for launch in August, will study the planet's high northern latitudes.
|An artist's conception shows a "Cryobot" melting
its way through the Martian ice beneath a lander.
Plaut said more ambitious missions to the layered deposits are already in the works. "There have been some proposals to use some clever ways to drill into these deposits from a lander or a rover," he said. "There are some devices that would melt through the material, and they would have to manage the liquid they produce. That's one way some of the new information we're getting could be fed through."
Some schemes call for sending "Cryobots" capable of melting their way through a few hundred yards (meters) of ice - then analyzing the water for signs of life using miniaturized lab equipment.
All this is music to the ears of Richard Hoover, who heads the astrobiology group at NASA's Marshall Space Flight Center. He and his colleagues have reported not only that the layered deposits contain abundant water ice, but also that the ice is subject to thawing and refreezing.
"The existence of water ice, and from time to time liquid water on Mars, is profoundly important to the existence of life on Mars," he told me today.
"What that means about the layered deposits of ice in the polar regions of Mars is that any microorganisms that were living when the ice melted would have been frozen into the polar cap, and would have been preserved intact, and may be even still alive," Hoover said. "You've got there a frozen record not only of life that may have inhabited the cap itself, but also may have been contained in cometary debris from elsewhere. All of this would have been put into deep-freeze cryopreservation, and could still be alive."
Even if microbes couldn't be reanimated, the ice could conceivably preserve the genes, the DNA or the biochemistry of Martian life. "Even a dead microorganism from Mars would be a great treasure," Hoover said. Assuming that the signs of life are preserved in the ice, scientists could learn whether or not life on Mars followed the same patterns seen on Earth.
"I have to say it could well be that life on Mars is exactly the same as life on Earth," Hoover said. Cosmic impacts could have blasted debris containing microbes into space - transferring the stuff of life from Earth to Mars, or vice versa, he said.
"We could easily have transferred Earth biology into space, where it could have been picked up by comets and transferred then to other regions of the solar system," he said.
Martian water ice could serve as an important resource for future life on the Red Planet as well, said Robert Zubrin, president of the Mars Society. For years, Zubrin has pressed for humans to settle on Mars sooner rather than later - and he said today's findings serve as just one more sign that Mars is a far better destination than the moon.
"All this defines Mars as the appropriate goal for human settlement as well as the search for life," Zubrin said.
Zubrin said the layered deposits might not be the best place to plunk down a settlement: At 70 degrees south latitude, the edges of the region are still not quite close enough to the equator for Zubrin's tastes. Nevertheless, he's heartened by the latest findings about frozen water.
"If it's everywhere at 70 degrees, then you may have it at isolated locations at 60. ... Looking at the data more closely, you may find places that not only have the water but also have interesting geological features," he said.
Zubrin isn't so heartened, however, by NASA's current focus on going back to the moon, and only then maybe moving on to Mars. He pointed to a 50-year outlook that NASA Administrator Michael Griffin wrote for Aviation Week, speculating that the space agency just might be able to send humans to Mars by the year 2037.
"When you say you're going to do something 30 years from now, you're basically saying you're not going to do it," Zubrin complained. "If you wanted to go to Mars in 2037, you could shut NASA down now, reopen it in 2020 and start from scratch. ... We really shouldn't be seeking to delay for a generation taking on the challenge of Mars."
NASA's take on the moon-vs.-Mars debate is that the moon has to serve as a close-at-hand test bed for eventual Mars missions - but Zubrin argued that many of those activities could take place on Earth, in the Arctic or Antarctic. "The goal should be Mars, and maybe for one of the early test flights we send people to the moon with some of the test hardware for Mars," he said.
In any case, Earth's polar regions are already being used as test beds in the scientific search for life in the deep freeze - whether on Mars, Europa or Enceladus. For example, Hoover is working on a U.S.-Russian expedition to Antarctica's subsurface lakes. A research group led by Stone Aerospace is also planning an Antarctic warmup for a mission to Europa.
Taken in this context, today's findings may seem to represent just one small step in the grand search for extraterrestrial life - but Plaut said that's the way giant leaps are done.
"This is more like science as it actually works, rather than science as people think it works," he said. "It's not one major discovery after another, but you build upon what people did before."
Update for 2:38 p.m. March 16: The Mars Express findings were a big topic of discussion at this week's Lunar and Planetary Science Conference, said the University of Arizona's William Boynton.
"People are excited about this. ... Five years ago, we didn't know there was any ice there, other than what was in the residual ice cap," he told me.
Then NASA's Mars Odyssey orbiter came along and detected the wide-ranging deposits of frozen water in the south polar region. Boynton is the principal investigator for the instrument that made the detection, Odyssey's gamma-ray spectrometer. He said the latest results move the ball forward by determining just how deep the deposits go.
Now Boynton is finishing up work on an instrument for the Mars Phoenix lander that could take the scientific ball even closer to the goal. The Thermal and Evolved-Gas Analyzer, or TEGA, could analyze the composition of dirt and ice samples from the Martian far north.
Phoenix's robotic arm should be able to dig through the first few inches of the Martian surface to the ice beneath, he said. Then it could either scrape up or grind off some of that ice to feed into the TEGA.
"One of the instrument's objectives is to look for organic chemistry. ... There's at least the chance we're going to find organic chemistry there," Boynton said. If Phoenix finds organics at work, that would become a bigger focus for future Mars missions, he said.
Other researchers already have designed a nuclear-powered probe system, called Multi-MICE, that could melt its way through Martian ice and analyze the water during its descent. "You can go many kilometers through the ice," James Powell of Plus Ultra Technologies told me.
The ice channels could lay bare millions of years of climate history on Mars - and perhaps the record of ancient life as well. Last year, Plus Ultra completed a Phase 1 study of the proposed mission for the NASA Institute for Advanced Concepts - here's a PDF file of its presentation on Multi-MICE.
Powell told me that the melt probes could represent just a first step toward turning the ice deposits into a base for human operations on Mars. "Basically, we feel it's an ideal place for the first landings," he said.
Plus Ultra's grand plan would be to melt tunnels into the ice, creating cavities where the water and other Martian materials could be robotically processed into fuel, oxygen and other necessities. "You can stockpile hundreds of tons of supplies under the ice," Powell said.