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Spacecraft spots possible signs of frozen water on the Moon

Evidence could uncover how oceans formed on Earth

Image credit: NASA's Goddard Space Flight Center/Scientific Visualization Studio

NASA’s Lunar Reconnaissance Orbiter has captured evidence that shows that parts of the Moon may be coated in thin bits of frost, and it could help scientists unlock the mystery of how water ended up on Earth.

The LRO has been in orbit since 2009, collecting vital information to aid space agencies in planning future human and robotic exploration of our satellite. But the latest results show that the data might help scientists understand Earth as well.

Measurements taken from the spacecraft’s Lunar Orbiter Laser Altimeter show that some of the craters in the south pole are covered in small bright spots. A reading of the surface temperatures reveals those regions are also the coldest, leading scientists to believe it could be frost reflecting light off the Moon’s surface.

“We found that the coldest places near the Moon’s south pole are also the brightest places – brighter than we would expect from soil alone – and that might indicate the presence of surface frost,” said Elizabeth Fisher, the lead author of the study published in Icarus and researcher at Brown University in Rhode Island.

The spots were found in “cold traps” – areas that do not receive direct sunlight. The temperature there remains below -163°C (-260°F), allowing ice to stay frozen for millions or billions of years.

Some scientists believe water on Earth might have been brought by icy asteroids or comets. If the frost is indeed ancient, it might be the leftover remnants of water brought by foreign rocky bodies, and could help scientists understand how oceans formed on Earth.

But if frost is the result of chemical reactions produced by the solar wind, it’ll be much younger. The researchers say both processes might have led to frost, with the old layers buried at the bottom and the newer layers on top.

The results are consistent with another study that looked at reflected starlight and the UV skyglow of hydrogen to reveal areas of elevated surface brightness. It provides further evidence that frost exists on the Moon, but researchers are still trying to understand why it only appears at the southern end.

“What has always been intriguing about the moon is that we expect to find ice wherever the temperatures are cold enough for ice, but that’s not quite what we see,” said Matt Siegler, co-author of the paper and researcher at the Planetary Science Institute in Arizona.

Frozen ice deposits in cold traps also exist on Mercury. But despite Mercury’s closer proximity to the Sun, it has up to 400 times more ice than the Moon. ®

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