Deep blue marks hydrogen-enriched soil that is as much as 50% ice in this Mars Odyssey neutron map of the planet.
Posted on 06/05/2002 4:28:25 PM PDT by Paul Ross
FRANK MORRING, JR./WASHINGTON
Scientists already are modifying Mars exploration plans to accommodate the discovery of vast quantities of water ice just beneath the planet's surface, with new kinds of data on the long-suspected finding possible as early as next year.
Deep blue marks hydrogen-enriched soil that is as much as 50% ice in this Mars Odyssey neutron map of the planet. |
NASA, which has built its Mars-exploration program on a "follow-the-water" strategy aimed at finding life or evidence of it, will shape its missions in the remainder of this decade and beyond against the knowledge that polar soils are as much as half water ice down to a depth of at least a meter. The Canada-sized layer of water mapped by the new Mars Odyssey orbiter could both support life and shield it from the deadly cosmic radiation that blasts the planet's surface.
A Mars Exploration Rover--two are set for launch next May and July--may be targeted on one of the hydrogen-rich zones Mars Odyssey has detected closer to the planet's equator. Researchers' best guess is that the hydrogen is chemically bound to minerals in the soil rather than in water ice, but a first-hand examination by a rover could clear that up.
Meanwhile, Europe's Mars Express, due for launch in June 2003, would use sounding radar from orbit to study the planet's makeup--including ice or liquid water--as deep as 5 km. (3.1 mi.) beneath the surface. Its Beagle 2 lander is targeted for a low-latitude site in the sedimentary Isidis Planitia, away from the ice zone identified by Odyssey, but the chances its instruments will find the evidence of life they were designed to seek can only be improved by the discovery.
NASA's Mars Reconnaissance Orbiter, launching in 2005, may be able to spot "blooms" of water vapor in the atmosphere, while proposals for "Scout" missions in 2007 are likely to be directly influenced by Odyssey's discovery. NASA's nuclear-powered long-duration "smart" rover would be able to roam the frozen polar plains at length after its launch in 2009, looking for water ice and related terrain to study.
 NASA/JPL/MALIN SPACE SCIENCE SYSTEMS |
| Mars Global Surveyor has found these polygonal landforms in the southern ice zone that resemble freeze/thaw terrain in Earth's Arctic. |
Ultimately, NASA's new space nuclear power initiative could develop power sources that will help the agency exploit the water it has found for robotic sample returns and human exploration. And past efforts to develop technology that can extract fuel and oxygen from the carbon dioxide atmosphere at Mars are likely to be superseded by the need for gear to break water into hydrogen and oxygen for propellant and life support.
"There's a lot of natural follow-up," said Jim Garvin, lead scientist for Mars exploration at NASA. "Some are built in; some would be focused directions on the program, and, of course, having samples back here on Earth from these kinds of regions . . . would be the ultimate."
Odyssey researchers said last week they have been able to quantify the amount of water ice below the surface around the south pole of Mars based on hydrogen detected by the spacecraft's Gamma Ray Spectrometer, Neutron Spectrometer and High-Energy Neutron Detector (AW&ST Apr. 1, p. 56). Below the surface south of about 60 deg. Lat. there is a shallow layer of relatively ice-free soil over a layer of "dirty ice" that gradually thickens toward the pole.
"We were hopeful that we could find evidence of ice, but what we have found is much more ice than we ever expected," said the University of Arizona's William Boynton, principal investigator on the instruments, who estimated there is enough water beneath the southern polar surface to fill Lake Michigan twice.
Preliminary data from the north polar regions, where the hydrogen is shielded by carbon dioxide frost during the Martian winter, also show hydrogen-rich soil there as frost recedes with the approach of spring.
 Dry surface soil covers an ice-rich layer that thickens toward the south pole of Mars, as shown in this schematic based on Mars Odyssey hydrogen-distribution data. |
"In a few months, as we get into Martian summer in the northern hemisphere, it will be exciting to see what lies beneath the cover of carbon dioxide dry ice as it disappears," said R. Stephen Saunders, Mars Odyssey project scientist at the Jet Propulsion Laboratory.
Since it arrived at the planet on Oct. 24, 2001, Odyssey's camera--known as the Thermal Emission Imaging System (Themis)--has also delivered data that may bear on the water history of Mars. In a presentation at the American Geophysical Union last week, Themis principal investigator Philip Christensen of Arizona State University said layering in the rock exposed in craters probably was caused by changes in the subsurface water table, although other causes are possible.
THE EXISTENCE OF WATER ICE in the polar regions of Mars had been suggested by the presence of terrain called patterned ground, which is also found in the Arctic, that has been imaged repeatedly by the Mars Global Surveyor (MGS) since September 1997. On Earth, a cycle of freezing and thawing produces characteristic polygons bounded by troughs or ridges, and the Mars Odyssey findings suggest the same phenomenon is at work on Mars. Like the water-ice deposits, the patterned ground is found between 60-80 deg. Lat. on Mars.
Just as MGS data suggest a water cycle on Mars when combined with the new findings from Mars Odyssey, Garvin said future science will be shaped by a desire to learn more about that cycle, both through the planet's seasons and across its history. The Mars Reconnaissance Orbiter is likely to be focusing its high-resolution imager in the high latitudes to look for seasonal changes caused by water, he said, and many proposals for in situ Mars instruments already deal with studying ground ice. One possible instrument for the 2009 lander is a gas chromatograph mass spectrometer like the ones that flew on the Viking landers, miniaturized with contemporary technology.
"Today a miniaturized version could measure things, such as aspects of the hydrogen in the soil, at 1,000 times better resolution than we did for Viking, and that would be fine enough to actually tell where the water came from," Garvin said. "Is it water that's fractionated from volcanoes erupting, or from a big reservoir of water on Mars, or from oceans?"
NASA's human-spaceflight operation has been studying in situ resource utilization for years as a way to reduce the launch mass for Mars exploration. Past efforts have focused on a Sabatier reactor that would combine hydrogen brought from Earth with Mars' carbon dioxide atmosphere to generate methane fuel and oxygen (AW&ST Mar. 18, 1996, p. 43). The discovery of water ice close to the surface could change that equation, according to Doug Cooke, manager of the Advanced Development Office at Johnson Space Center.
"Water, of course, is useful in its own right in terms of consumables if you send people there," Cooke said. "Then you can break it down, of course, and make hydrogen and oxygen . . . for atmosphere makeup [and] fuel."
Living off the land at Mars requires electric power to drive the necessary chemical reactions, and NASA is pushing for new nuclear technology to produce power in space (AW&ST May 20, p. 64). Cooke said past in situ resource utilization plans have focused on solar powers.
"If you have nuclear energy available, that really simplifies that problem," he said.
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Some of the old timers even claimed to see green stuff "growing" alongside the waterways, or whatever they were.
A week or so ago, there was an article to the effect that some scientists with a connection to NASA have data which they suspect might indicate the presence of some amount of some substance which may be water under the surface of the Red Planet. Now, suddenly, we have a massive discovery of H2O on Mars.
Someone refresh my memory, please. Just how many bajillion squadrillion bucks did we spend to get that remote-control rover on Mars to inform us that some of the rocks were reddish-brown while others were brownish-red, that some were larger than others, and that their shapes varied?
Tell ya what, Congress. I'm a reasonable guy. For every dollar you cut from foreign aid (n.b., "cut" means a reduction from current spending, not a reduction in budgets for future years), you may spend a dollar on a Mars mission. Inasmuch as those are, in part, my dollars we're talking about, I think that's a square deal.
EXNASA
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