NASA has discovered signs of frost on the lunar surface using Lunar Reconnaissance Orbiter. The scientists have said that bright areas in the craters near the south pole of the Moon have been identified that are cold enough to have frost present on the lunar 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 the journal Icarus.
Appearing to be patchy and thin, the icy deposits are possibly mixed in with the surface layer of soil, dust and small rocks known as regolith.
However, the scientists said that expanses of ice similar to frozen pond or skating rink are not seen but they have seen what appear to be signs of surface frost.
The cold traps are the permanently dark areas that are located either on the floor of a deep creater or along a section of crater wall which does not receive direct sunlight, where temperatures remain below minus 163 degrees Celsius.
Water ice can persist for millions or billions of years under such conditions. One of the driving goals of Lunar Reconnaissance Orbiter, or LRO, which has been orbiting the Moon since 2009, has been to understand the nature of these deposits.
Fisher from the University of Hawai’i at Manoa, and her colleagues found evidence of lunar frost by comparing temperature readings from LRO’s Diviner instrument with brightness measurements from the spacecraft’s Lunar Orbiter Laser Altimeter, or LOLA.
It was observed in these comparisons that the coldest areas near the south pole were also very bright. This indicated that there was a presence of ice or other highly reflective materials.
The researchers looked at the peak surface temperatures, because water ice won’t last if the temperature creeps above the crucial threshold.
The study strengthens the case that there is frost in cold traps near the Moon’s south pole. So far, however, researchers have not seen the same signs near the Moon’s north pole.
“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, a researcher with the Planetary Science Institute in Dallas, and a co-author on the study.