Latest findings shed light on the history and origins of water on the lunar surface
A year after NASA scientists confirmed evidence of water ice on the moon's surface, they have now found proof of water being released from the surface of the moon due to impact from micro or very small meteorites.
Data from NASA’s Lunar Atmosphere and Dust Environment Explorer or LADEE probe of 2013-14 revealed how streams of meteoroids striking the moon’s thin atmosphere make it release water vapor.
“We traced most of these events to known meteoroid streams, but the really surprising part is that we also found evidence of four meteoroid streams that were previously undiscovered,” Mehdi Benna of NASA’s Goddard Space Flight Center and the lead author of the study, said.
Till now, scientists had the evidence of presence of water (H2O) and hydroxyl (OH) on the moon. However, the origins of the water, whether it is widely distributed and how much is actually present still remains a mystery.
“The moon doesn’t have significant amounts of H2O or OH in its atmosphere most of the time. But when the moon passed through one of these meteoroid streams, enough vapor was ejected for us to detect it. And then, when the event was over, the H2O or OH went away,” said Richard Elphic, LADEE project scientist at NASA’s Ames Research Centre.
NASA explains that the lunar surface composition can be divided into three layers — a bone-dry top layer, a thin transition layer and a hydrated layer, where water molecules stick to bits of soil and rock called regolith.
The researchers estimate that the “hydrated layer has a water concentration of about 200 to 500 parts per million, or about 0.02 to 0.05 per cent by weight.” This means that it is still extremely dry even compared to the driest places on earth.
When a meteorite penetrates the lunar surface by at least 3 inches (8 centimeters), it causes the water vapor release. Since the surface is “fluffy”, even a meteoroid that’s a fraction of an inch across can penetrate far enough to release a puff of vapor.
Two-third of the vapor escapes into space, while one-third lands back on the surface of the moon. The study, as per media reports, estimates that over the course of a year meteorites set free about 300 metric tonnes of water from the moon’s soil.
Further, the analysis indicates that meteoroid impacts release water faster than it can be produced from reactions. “The water being lost is likely ancient, either dating back to the formation of the Moon or deposited early in its history,” said Benna.
Scientists aim to use the results, published in Nature Geosciences, to further explore the history of water and its origins on the moon.
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