"What's important now is that we don't have use terms like 'gobs' and 'whopping huge' amounts of subsurface water ice," said William Boynton, principal investigator for Odyssey's gamma ray spectrometer suite at the University of Arizona, Tucson.
"I'd have to give the instrument an A-plus. It's doing everything we expected, and more so," Boynton told SPACE.com.
Researchers have concluded the hydrogen detected is not distributed uniformly over the upper 3 feet (one-meter). Rather, it is much more concentrated in a lower layer beneath the top-most surface.
Boynton said that the amount of hydrogen detected indicates 20 to 50 percent ice by mass in the lower layer. Because rock has a greater density than ice, this amount is more than 50 percent water ice by volume.
Heating a full bucket of this ice-rich polar soil would yield more than half a bucket of water, Boynton said.
"There's really an awful lot of water that's in there when you melt it," he said.
Priming the pump
Boynton said there's much more work needed before dispatching astronauts to the red planet. But knowing an ample supply of underground water ice exists on Mars ahead of time clearly primes the pump, so to speak, he said.
"There's enough water there that astronauts don't have to worry about bringing water along with them," Boynton said.
"All you have to do is heat it up and the water is going to run out. You just put it through a filternothing any more elaborate than the kind of filter you'd use on your coffee pot," Boynton said. "My guess is that it would be clean enough to drink right like that," he said.
Boynton added, however, that astronauts would have to be on their guard not to drink contaminated water. "If you melted the ice and you found too much bacteria.well, actually that would be great news. It means you've got life on Mars," he said.
"They could always boil the water and not have to worry about bacteria. My guess is, based on everything we know at Mars is that water would be pretty pure, with no organic matter in it at all," Boynton said.
Designing a future Mars lander to dig down and sample the ice layer, heat it up, and measure its organic content would be a straightforward experiment, Boynton said. "Obviously, it would be very useful to bring some of this ice back to Earth labs and study it in detail," he said.
Climate story
Bruce Jakosky, an astrobiologist at the University of Colorado in Boulder, said the Odyssey data points to a climate story, rather than a biology tale. "The big thing is that the water ice detected in the regolith [the top layer of Mars] appears to be most consistent with it being deposited via vapor exchange with the atmosphere," he said.
Odyssey is "telling us more about climate and climate history than about biology, Jakosky said. "At present, there is no way to warm this water ice enough to get even trace amounts of liquid. The ice is in equilibrium with atmospheric vapor," he said.
Given Mars temperature, this is way below the melting point under any reasonable or realistic conditions, Jakosky said. The new Mars data is spelling out an important climate story, he said.
"It tells us about the atmospheric water cycle and, by implication, the polar water cycle and the history of climate over the last few hundred thousand or million years. It's one more very important piece of the puzzle that we are putting together on how water behaves on all time-scales and what the nature of the climate is," he said.
Unseen planet
"Mars never fails to surprise," said Jim Garvin, Mars Program Scientist at NASA Headquarters in Washington, D.C.
Odyssey's observations show the strength of NASA's Mars strategy of "follow the water," Garvin said. "Our 'science catch phrase' has proven amazingly resilient and has maintained its relevance. Finding gobs of hydrogen-bearing stuff, which Boynton and team are interpreting as water ice, in new places and at new concentrationsbolsters our approach," he said.
Garvin said that Odyssey also shows that as measurement perspectives on Mars change -- from imaging to the infrared and now neutrons and the like -- "we see yet more of the 'previously unseen' planet," he said.
Finding water ice in abundance today on Mars means that follow-up spacecraft are going to be busy.
For instance, a U.S.-Italian-built radar onboard the European Space Agency's Mars Express will look deep below Mars' surface. Mars Express is now being readied for a June 2003 liftoff.
In addition, NASA's Mars Reconnaissance Orbiter, to be rocketed toward the red planet in 2005, totes along a subsurface sounding radar to probe at shallow depths and a high-tech hyperspectral imager too.
Something amazing
"It's my own view that the Odyssey findings that Boynton and team have given us further strengthens the possibilities that Mars is hiding something amazing," Garvin said.
"I'll bet that we have not seen anything yet.... and just wait till those Mars Exploration Rovers start ambling around in early 2004," Garvin said.
Odyssey's revelations, Garvin said, will not alter NASA's step-by-step plan to explore Mars.
Garvin said that NASA's Mars Exploration Program strategy is both vindicated and re-affirmed with Odyssey's results. Moreover, the probe has much more to offer in months to come.
"Mars will not let us down," Garvin concluded.
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