Scientists have long speculated about the source of significant quantities of hydrogen that have been observed at the lunar poles, and just a few months ago NASA announced that water molecules were indeed present, but in relatively small amounts. Now the Lunar CRater Observing and Sensing Satellite (LCROSS) that was employed to shed some more light on the presence of water on the moon, looks like it has done just that with preliminary data indicating the mission successfully uncovered water in a permanently-shadowed crater.
As reported previously, the LCROSS spacecraft and a companion rocket stage made twin impacts in the Cabeus crater on October 9 creating a plume of material from the bottom of a crater that had not seen sunlight in billions of years. Moving at a speed of more than 1.5 miles per second, the spent upper stage of its launch vehicle hit the lunar surface creating an impact that instruments aboard LCROSS observed for approximately four minutes before LCROSS followed the upper stage into the surface just five minutes later.
The plume traveled at a high angle beyond the rim of Cabeus and into sunlight, while an additional curtain of debris was ejected more laterally. Since the impacts, the LCROSS science team has been analyzing the huge amount of data the spacecraft collected. The team concentrated on data from the satellite's spectrometers, which provide the most definitive information about the presence of water. A spectrometer helps identify the composition of materials by examining light they emit or absorb.
Additional confirmation came from an emission in the ultraviolet spectrum that was attributed to hydroxyl, a product from the break-up of water by sunlight. When atoms and molecules are excited, they release energy at specific wavelengths that can be detected by the spectrometers. A similar process is used in neon signs. When electrified, a specific gas will produce a distinct color. Just after impact, the LCROSS ultraviolet visible spectrometer detected hydroxyl signatures that are consistent with a water vapor cloud in sunlight.
"We are ecstatic," said Anthony Colaprete, LCROSS project scientist and principal investigator at NASA's Ames Research Center in Moffett Field, California. "Multiple lines of evidence show water was present in both the high angle vapor plume and the ejecta curtain created by the LCROSS Centaur impact. The concentration and distribution of water and other substances requires further analysis, but it is safe to say Cabeus holds water."
The LCROSS findings suggest that water could be more widespread and in greater quantities than previously suspected. If the water that was formed or deposited is billions of years old, these polar cold traps could hold a key to the history and evolution of the solar system, much as an ice core sample taken on Earth reveals ancient data. In addition, water and other compounds represent potential resources that could sustain future lunar exploration.
Data from the other LCROSS instruments are being analyzed for additional clues about the state and distribution of the material at the impact site. The LCROSS science team and colleagues are poring over the data to understand the entire impact event, from flash to crater. The goal is to understand the distribution of all materials within the soil at the impact site.
"The full understanding of the LCROSS data may take some time. The data is that rich," Colaprete said. "Along with the water in Cabeus, there are hints of other intriguing substances. The permanently-shadowed regions of the moon are truly cold traps, collecting and preserving material over billions of years."
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