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frojack writes:

Science Alert has a story about a long running Lunar temperature measurement that apparently was lost and forgotten for decades.

Between 1971 and 1977, Apollo scientists conducting experiments on the Moon discovered that the surface of our li'l satellite buddy got mysteriously warmer. But the data from 1974 onwards went missing, and the strange warming phenomenon remained an enigma. The experiment was called the heat flow experiment, and it was designed to determine the rate at which the interior of the Moon loses heat.

Astronauts with Apollo 15 and 17 drilled holes into the lunar surface, up to depths of 2.3 metres, and probes measured the temperature at several depths in the holes.

These were long-term experiments, left in place after the astronauts departed, and transmitting data back to Earth.

The measurements revealed that the temperature of the moon at all measured depths got warmer from the date the experiment started in 1971 all the way till measurements ended in 1977.
That's a relatively short period of time on a planetary time frame. A rate of warming that rapid would have the moon surface incandescent well before we were began squabbling over who got to live in the best caves.

Various theories were put forth, but in the end people pretty much agreed it must be our fault.

In typical NASA fashion, the data was archived on tape, filed in the tape vault, and promptly forgotten, lost, moved, etc. Decades later, someone went looking for it. Some 440 tapes were found, (less than 10%) badly degraded over time. Some were recovered, Logs (written ones on that old unreliable medium: Paper) were found and when combined these sources recovered significant portions of the long lost data.

After 8 years of analysis, the data showed that the warming continued, all the way through until the end of observations in 1977. It also showed that, closer to the surface, the warming was more pronounced; and the warmth reached the shallower depths sooner, suggesting that the warming was occurring from the surface down, rather than radiating out from the Moon's interior.

So were the astronauts doing that? The researchers believe that their movements were disturbing the dirt on the lunar surface.

"Recently acquired images of the Lunar Reconnaissance Orbiter Camera over the two landing sites show that the regolith on the paths of the astronauts turned darker, lowering the albedo," they wrote in their paper.

"We suggest that, as a result of the astronauts' activities, solar heat intake by the regolith increased slightly on average, and that resulted in the observed warming."

In other words, when they stomped about and drove lunar rovers all over the landing sites, the Apollo astronauts overturned the topsoil, exposing darker regolith underneath. Darker surfaces don't reflect as much light; instead, they absorb it.

So this darker lunar surface at the Apollo sites absorbed more of the Sun's heat, raising the Moon's surface temperature by a few degrees.

Original Submission