LUNAR PROSPECTOR FINDS EVIDENCE OF ICE AT MOON'S POLES



March 5, 1998



Douglas Isbell
Headquarters, Washington, DC
(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)

<h4>Release: H98-38</h4> <h3>Lunar Prospector Finds Evidence of Ice at 
Moon's Poles</h3> 

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.



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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 near-side 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 near-side 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.



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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:



http://lunar.arc.nasa.gov

	
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