Discovery of Lunar Water Making Scientific Splash

By Roy Mark  |  Posted 2009-09-26

Space, it turns out, is a wetter place than scientists originally imagined or theorized. NASA this week revealed water molecules in the polar regions of the moon have been discovered and that Mars has much more water than scientists previously thought. While the amount of ice spotted on Mars is surprising, it was the discovery of ice on the moon that scientists found most interesting.

"Water ice on the moon has been something of a holy grail for lunar scientists for a very long time," Jim Green, director of the Planetary Science Division at NASA Headquarters in Washington, D.C., said in a statement. The discovery opens the possibility of visiting astronauts perhaps squeezing water out of the lunar soil.

NASA's Moon Mineralogy Mapper, or M3, instrument first detected the lunar ice. Launched into space in 2008 aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft, M3's spectrometer measured light reflecting off the moon's surface at infrared wavelengths, splitting the spectral colors of the lunar surface into small enough bits to reveal a new level of detail in surface composition.

When the M3 science team analyzed data from the instrument, they found the wavelengths of light being absorbed were consistent with the absorption patterns for water molecules and hydroxyl, a molecule consisting of one oxygen atom and one hydrogen atom. Data from the Visual and Infrared Mapping Spectrometer on NASA's Cassini spacecraft and the High-Resolution Infrared Imaging Spectrometer on NASA's Epoxi spacecraft contributed to confirmation of the finding.

The M3 team found water molecules and hydroxyl at diverse areas of the sunlit region of the moon's surface, but the water signature appeared stronger at the moon's higher latitudes. Water molecules and hydroxyl previously were suspected in data from a Cassini flyby of the moon in 1999, but the findings were not published until now.

"With our extended spectral range and views over the north pole, we were able to explore the distribution of both water and hydroxyl as a function of temperature, latitude, composition and time of day," Jessica Sunshine, Epoxi's deputy principal investigator and a scientist on the M3 team, said. "Our analysis unequivocally confirms the presence of these molecules on the moon's surface and reveals that the entire surface appears to be hydrated during at least some portion of the lunar day."

While the confirmation of ice on the moon was a sensation among scientists, many were equally surprised to find frozen water hiding just below the surface of mid-latitude Mars. NASA's Mars Reconnaissance Orbiter observed the Martian ice after meteorites excavated fresh craters on the Red Planet.

The finds indicate water-ice occurs beneath Mars' surface halfway between the north pole and the equator, a lower latitude than expected in the Martian climate. Some of the craters show a thin layer of bright ice atop darker underlying material. The bright patches darkened in the weeks following initial observations, as the freshly exposed ice vaporized into the thin Martian atmosphere. One of the new craters had a bright patch of material large enough for one of the orbiter's instruments to confirm it is water-ice.

"We now know we can use new impact sites as probes to look for ice in the shallow subsurface," said Megan Kennedy of Malin Space Science Systems in San Diego, Calif., a  member of the team operating the orbiter's Context Camera.

According to NASA, the Context Camera sends more than 200 images of Mars per week, covering a total area greater than California. The NASA team pours over each image, sometimes finding dark spots that fresh, small craters make in terrain covered with dust. Checking earlier photos of the same areas can confirm a feature is new. The team has found more than 100 fresh impact sites, mostly closer to the equator than the ones that revealed ice.

Mars Reconnaissance Orbiter Project Scientist Rich Zurek said, "This mission is designed to facilitate coordination and quick response by the science teams. That makes it possible to detect and understand rapidly changing features."

The ice exposed by fresh impacts suggests that NASA's Viking Lander 2, digging into mid-latitude Mars in 1976, might have struck ice if it had dug just four inches deeper. The Viking 2 mission, which consisted of an orbiter and a lander, launched in September 1975 and became one of the first two space probes to land successfully on the Martian surface. 

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