Doesn't water mean the possibility of life, past or present ?
LUNAR PROSPECTOR FINDS EVIDENCE OF ICE AT MOON'S POLES
Nasa RELEASE: 98-38 - March 1998
There is a high probability that water ice exists at both the north and south poles of the Moon, according to initial scientific data returned by NASA's Lunar Prospector.
The Discovery Program mission also has produced the first operational gravity map of the entire lunar surface, which should serve as a fundamental reference for all future lunar exploration missions, project scientists announced today at NASA's Ames Research Center, Moffett Field, CA.
Just two months after the launch of the cylindrical spacecraft, mission scientists have solid evidence of the existence of lunar water ice, including estimates of its volume, location and distribution. "We are elated at the performance of the spacecraft and its scientific payload, as well as the resulting quality and magnitude of information about the Moon that we already have been able to extract," said Dr. Alan Binder, Lunar Prospector Principal Investigator from the Lunar Research Institute, Gilroy, CA.
The presence of water ice at both lunar poles is strongly indicated by data from the spacecraft's neutron spectrometer instrument, according to mission scientists. Graphs of data ratios from the neutron spectrometer "reveal distinctive 3.4 percent and 2.2 percent dips in the relevant curves over the northern and southern polar regions, respectively," Binder said. "This is the kind of data 'signature' one would expect to find if water ice is present."
However, the Moon's water ice is not concentrated in polar ice sheets, mission scientists cautioned. "While the evidence of water ice is quite strong, the water 'signal' itself is relatively weak," said Dr. William Feldman, co-investigator and spectrometer specialist at the Department of Energy's Los Alamos National Laboratory, NM. "Our data are consistent with the presence of water ice in very low concentrations across a significant number of craters." Using models based on other Lunar Prospector data, Binder and Feldman predict that water ice is confined to the polar regions and exists at only a 0.3 percent to 1 percent mixing ratio in combination with the Moon's rocky soil, or regolith.
How much lunar water ice has been detected? Assuming a water ice depth of about a foot and a half (.5 meters) -- the depth to which the neutron spectrometer's signal can penetrate -- Binder and Feldman estimate that the data are equivalent to an overall range of 11 million to 330 million tons (10-300 million metric tons) of lunar water ice, depending upon the assumptions of the model used. This quantity is dispersed over 3,600 to 18,000 square miles (10,000-50,000 square kilometers) of water ice- bearing deposits across the northern pole, and an additional 1,800 to 7,200 square miles (5,000-20,000 square kilometers) across the southern polar region. Furthermore, twice as much of the water ice mixture was detected by Lunar Prospector at the Moon's north pole as at the south.
Dr. Jim Arnold of the University of California at San Diego previously has estimated that the most water ice that could conceivably be present on the Moon as a result of meteoritic and cometary impacts and other processes is 11 billion to 110 billion tons. The amount of lunar regolith that could have been "gardened" by all impacts in the past 2 billion years extends to a depth of about 6.5 feet (2 meters), he found. On that basis, Lunar Prospector's estimate of water ice would have to be increased by a factor of up to four, to the range of 44 million to 1.3 billion tons (40 million to 1.2 billion metric tons). In actuality, Binder and Feldman caution that, due to the inadequacy of existing lunar models, their current estimates "could be off by a factor of ten in either direction."
The earlier joint Defense Department-NASA Clementine mission to the Moon used a radar-based technique that detected ice deposits in permanently shadowed regions of the lunar south pole. It is not possible to directly compare the results from Lunar Prospector to Clementine because of their fundamentally different sensors, measurement
"footprints," and analysis techniques. However, members of the Clementine science team concluded that its radar signal detected from 110 million to 1.1 billion tons (100 million to 1 billion metric tons) of water ice, over an upper area limit of 5,500 square miles (15,500 square kilometers) of south pole terrain.
There are various ways to estimate the economic potential of the detected lunar water ice as a supporting resource for future human exploration of the Moon. One way is to estimate the cost of transporting that same volume of water ice from Earth to orbit. Currently, it costs about $10,000 to put one pound of material into orbit. NASA is conducting technology research with the goal of reducing that figure by a factor of 10, to only $1,000 per pound. Using an estimate of 33 million tons from the lower range detected by Lunar Prospector, it would cost $60 trillion to transport this volume of water to space at that rate, with unknown additional cost of transport to the Moon's surface.
From another perspective, a typical person consumes an estimated 100 gallons of water per day for drinking, food preparation, bathing and washing. At that rate, the same estimate of 33 million tons of water (7.2 billion gallons) could support a community of 1,000 two-person households for well over a century on the lunar surface, without recycling.
"This finding by Lunar Prospector is primarily of scientific interest at this time, with implications for the rate and importance of cometary impacts in the history and evolution of the Solar System," said Dr. Wesley Huntress, NASA Associate Administrator for Space Science. "A cost-effective method to mine the water crystals from within this large volume of soil would have to be developed if it were to become a real resource for drinking water or as the basic components of rocket fuel to support any future human explorers."
Before the Lunar Prospector mission, historical tracking data from various NASA Lunar Orbiter and Apollo missions had provided evidence that the lunar gravity field is not uniform. Mass concentrations caused by lava which filled the Moon's huge craters are known to be the cause of the anomalies. However, precise maps of lunar mass concentrations covering the moon's equatorial nearside region were the only ones available.
Lunar Prospector has dramatically improved this situation, according to co-investigator Dr. Alex Konopliv of NASA's Jet Propulsion Laboratory, Pasadena, CA. Telemetry data from Lunar Prospector has been analyzed to produce a full gravity map of both the near and far side of the moon. Konopliv also has identified two new mass concentrations on the Moon's nearside that will be used to enhance geophysical modeling of the lunar interior. This work has produced the first-ever complete engineering-quality gravity map of the moon, a key to the operational safety and fuel-efficiency of future lunar missions.
"This spacecraft has performed beyond all reasonable expectations," said NASA's Lunar Prospector mission manager Scott Hubbard of Ames. "The findings announced today are just the tip of the iceberg compared to the wealth of information forthcoming in the months and years ahead."
Lunar Prospector is scheduled to continue its current primary data gathering mission at an altitude of 62 miles (100 kilometers) for a period of ten more months. At that time, the spacecraft will be put into an orbit as low as six miles (10 kilometers) so that its suite of science instruments can collect data at much finer resolution in support of more detailed scientific studies. In addition, surface composition and structure information developed from data returned by the spacecraft's Gamma Ray Spectrometer instrument will be a crucial aspect of additional analysis of the polar water ice finding over the coming months.
The third launch in NASA's Discovery Program of lower cost, highly focused planetary science missions, Lunar Prospector is being implemented for NASA by Lockheed Martin, Sunnyvale, CA, with mission management by NASA Ames. The total cost to NASA of the mission is $63 million.
Additional informaiton about the Lunar Prospector mission can be found on the Internet at URL:
Douglas Isbell Headquarters, Washington, DC March 5, 1998 (Phone: 202/358-1753)
David Morse Ames Research Center, Moffett Field, CA (Phone: 650/604-4724)
John Gustafson Los Alamos National Laboratory, Los Alamos, NM Department of Energy (Phone: 505/665-9197)
John Watson Jet Propulsion Laboratory, Pasadena, CA (Phone: 818/354-6478)
Old press releases and stories
Scientists Report Water May Be Present on Moon
December 4, 1996
By JOHN NOBLE WILFORD
Scientists think they have detected water on the Moon, and suddenly visions of people living in lunar colonies and stopping off there to refuel on the way to Mars seem a little less farfetched.
After two years of careful analysis, scientists said Tuesday that radar signals from an American spacecraft indicated the Moon was not as bone-dry as is usually thought. The peculiar radar signatures suggested the presence of water ice in the permanently cold shadows of a deep basin near the lunar south pole.
The ice deposit is not at all like a frozen lake where astronauts might try skating in one-sixth gravity. Instead, the scientists said, the survey seemed to reveal a vast landscape of some 3,000 square miles in which ice crystals are mixed with dirt, a kind of permafrost that is presumably the residue of moisture from comets striking the Moon over the last three billion years.
"We think we have found ice," said Dr. Paul D. Spudis, a geologist at the Lunar and Planetary Institute in Houston. "We are not positive. But we see signals consistent with ice, and we think it's there."
But Spudis and other scientists reporting the findings by Clementine, a small Defense Department spacecraft, acknowledged that the discovery needed to be confirmed by an independent investigation. That could come a year from now when another spacecraft, Lunar Prospector, is to orbit the Moon with instruments with even greater precision for determining the presence of lunar water.
A detailed report on the findings has been published in the current issue of the journal Science. The principal scientists, Spudis and Dr. Stewart Nozette of the Air Force Phillips Laboratory in Alexandria, Va., described the results at a news conference Tuesday at the Pentagon.
Other scientists reacted to the report with a mixture of caution and enthusiasm. They wanted to believe, because of the important implications for future exploration and colonization of the Moon. But they noted that the radar results were particularly difficult to interpret.
"I'd be delighted if it's true," said Dr. Bruce C. Murray, a planetary scientist at the California Institute of Technology in Pasadena, who in 1961 predicted that water ice would be found in polar shadows. "But we need to look very carefully at the interpretation and wait for confirmation."
In the journal article, the discovery team also was extremely cautious. "There are several possible explanations for these observations," the scientists wrote, "including the possibility" that the signals do not result from ice deposits.
But no one was ignoring the implications, if the ice proved to be real.
In a statement issued by the National Aeronautics and Space Administration, Dr. Wesley T. Huntress Jr., the agency's associate administrator for science, said the likely existence of water ice on the Moon "could be a key ingredient in the support of future human lunar exploration, due to its potential value as a source of the components of rocket fuel."
The discovery has "changed a desert to an oasis," said John E. Pike, a space policy analyst at the Federation of American Scientists in Washington. "The Moon used to be dry, now it's wet. Now it could become a gas station."
Ever since Murray's prediction in 1961, the possibility of ice on the Moon has inspired speculation about using the resource for people living in permanent outposts and as rocket fuel for interplanetary travel. Using solar or nuclear power, the water ice could be converted into its components, hydrogen and oxygen, which are valuable rocket fuels.
But Dr. John M. Logsdon, director of the Space Policy Institute at George Washington University, said it was still not clear how practical a resource the polar ice would be. He questioned the economic feasibility of using the water for colonies or rocket fuel in the foreseeable future.
As the Clementine spacecraft discovered, the dominant topographic feature in the south polar region of the Moon is a huge depression called the South Pole-Aitken basin. Gouged out by a massive asteroid nearly four billion years ago, the basin stretches 1,500 miles and in places is as deep as eight miles, deeper than Mount Everest is high.
It is in the shadow of these deep walls that the cometary ice has apparently accumulated as a mixture of dirt and rock. Temperatures in the shadows are estimated to be as low as minus 387 degrees Fahrenheit. Any ice in parts of the basin exposed to sunlight would have evaporated and escaped into space. As it is, Spudis said, the ice in shadows is not a solid sheet like a skating rink, but constitutes probably no more than 10 percent of the material in the region, mostly dirt.
The ice's being near the south pole is another reason some scientists gave for expressing reservations about its utility any time soon.
In a book "Mining the Sky," published last month by Addison Wesley, Dr. John S. Lewis, a geologist at the Space Engineering Research Center of the University of Arizona, wrote that in many respects "the lunar poles are not an attractive site for the lunar base." They are harder to reach by spacecraft from Earth and require more rocket energy. And it would be a difficult engineering feat to transport the ice to a base closer to the equator.
Spudis noted that there was a high point in the basin, near the actual pole, that is almost permanently in sunlight. This would be an excellent site, he said, for a lunar installation with solar power panels to run equipment to melt the ice for water or convert it to breathing oxygen or rocket fuel.
But he conceded: "We have a long way to go before we have people living on the Moon. What this is, is an indication that living on the Moon might be possible."
From an astronaut on the space shuttle Columbia came an even more optimistic response. Told of the new findings by Mission Control, Dr. Story Musgrave said, "Clearly if there is ice and there is water out there, that is a natural resource which is extraordinarily important to establishing a permanent thing such as an observatory on the Moon, or some kind of colony."
Nozette said the scientists were almost certain the radar was detecting water ice, though there could be small amounts of other substances like methane or carbon dioxide mixed in. Some 90 percent of a comet is composed of ice and most of that is water ice.
About one-third of the south polar region appeared to be in permanent shadow, the Clementine scientists said, but very little of the north pole is in shadow.
The $80 million Clementine spacecraft was developed and launched by the Defense Department's Ballistic Missile Defense Organization to test sensing instruments for anti-missile defenses. Since the craft would be heading near the Moon, where some of the tests could be made, scientists got permission to put Clementine into a lunar orbit and re-map in greater detail much of the surface.
Clementine was launched in January 1994 and operated in lunar orbit for four months. It was the first American craft to explore the Moon since the final Apollo landing in December 1972 and the last visit by any craft since the unmanned Russian Luna 24 landed there in 1976, picked up rock samples and returned them to Earth.
The next mission to the Moon is Lunar Prospector, a small unmanned craft being developed for NASA by the Ames Research Center in Mountain View, Calif., and built by Lockheed-Martin Corp. in Denver. Scheduled for launching next September, the spacecraft is to go into an orbit of the Moon that repeatedly crosses both poles. Its five remote-sensing instruments are designed to map the composition of the lunar surface and observe its magnetic and gravity fields.
Huntress of NASA said that Lunar Prospector's two neutron spectrometers should be able to measure the amount of hydrogen on the lunar surface to an accuracy of 50 parts per million. "This will permit scientists to infer the presence or absence of ice with greater precision than possible via the innovative but indirect method used by the Clementine team," he said.
Copyright 1996 The New York Times