Today at Brown

In a discovery that promises to reinvigorate studies of the moon and potentially upend thinking of how it originated, scientists at Brown and other research institutions have found evidence of water molecules on the surface of the moon. Scientists involved in the discovery believe as much as 1,000 water molecule parts per million could be in the lunar soil; harvesting one ton of the top layer of the moon’s surface would yield as much as 32 ounces of water.

Carle Pieters, professor of geological sciences, is the lead author of a Science paper that reports evidence of water in the moon’s high latitudes — greatly expanding current thinking about where water in any form was presumed to be located. “We’ve made a very important step with this discovery, and now there are some very important steps to follow up on,” Pieters says.

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Carle Pieters, professor of Geological sciences, speaks at a NASA press conference. [Courtesy: NASA]

Pieters is the lead investigator on the Moon Mineralogy Mapper (M3), a NASA instrument that was carried into space on Oct. 22, 2008, aboard the Indian Space Research Organization’s Chandrayaan-1 spacecraft. She said the findings from M3 reveal interesting new questions about where the water molecules come from and where they may be going. Scientists have speculated that water molecules may migrate from non-polar regions of the moon to the poles, where they are stored as ice in ultra-frigid pockets of craters that never receive sunlight.

“If the water molecules— even a fraction of them — are as mobile as we think they are,” Pieters says, “they provide a mechanism for getting water to those permanently shadowed craters. This opens a whole new avenue [of lunar research]. But we have to understand the physics of it to ultilize it.”

The M3 team found water molecules and hydroxyl in diverse areas of the sunlit region of the moon’s surface, but the water signature appeared stronger at the moon’s higher latitudes. The M3 discovery was confirmed by data from two NASA spacecraft — the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft and the High-Resolution Infrared Imaging Spectrometer on the EPOXI spacecraft. Data from those missions also are being published in separate papers in Science.

Other Brown faculty listed as contributing authors to the M3 paper include Brown Professor James Head III and John “Jack” Mustard; postdoctoral research associates Rachel Klima and Jeffrey Nettles; and graduate student Peter Isaacson.

Lunar water This lunar crater image from the M3 mapper shows water-rich minerals in blue. (NASA/Brown) Isaacson says the M3 results were a huge surprise: “This discovery turns a lot of the conventional thinking about the lunar surface on its head.” Mustard, who has had major findings of water-bearing minerals on Mars, says the moon discovery is “intriguing, because it shows water on a planet that we weren’t anticipating, and it’s in a form that’s mysterious.”

M3’s state-of-the-art 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.

“For silicate bodies, such features are typically attributed to water and hydroxyl-bearing materials,” Pieters says. “When we say ‘water on the moon,’ we are not talking about lakes, oceans, or even puddles. Water on the moon means molecules of water and hydroxyl that interact with molecules of rock and dust specifically in the top millimeters of the moon’s surface.”

The research was funded by NASA.