Through recovering the lost tapes of Apollo moon missions, scientists finally have an answer on why the lunar surface became bizarrely warmer during the 1970s.

The Apollo 15 and 17 missions in 1971 and 1972 involved the deployment of probes that measured the heat coming from the moon's interior. Raw temperature data from these probes were subsequently transmitted to NASA Johnson Space Center in Houston until 1977.

Scientists who analyzed this data observed a strange uptick in the temperature from the moon's surface. The uptick was monitored all throughout after the Apollo missions started in 1971 until when the probes stopped generating records in 1977.

For decades, this peculiar temperature from the moon baffled experts. They had few theories: the astronaut's activity in the moon propelled this eerie temperature rise, the moon's changing orbit brought about the change in the heat, or the heat itself was excess radiation coming from Earth.

The Mystery Of Apollo Missions

The probes for the Apollo 15 and 17 missions were designed to measure the heat flow from the moon's core. Scientists wanted to understand whether the moon's interior was as hot as the Earth's. They also wanted to measure how much heat does moon's rocks and mantle could produce.

The experiment ran until 1977, but only tapes from 1971 to 1974 were preserved at NASA's National Space Science Data Center. The tapes from 1975 to 1977 were never preserved and were lost since the project ended.

The lost tapes were finally recovered some eight years ago. The whole time from when the tapes where recovered, a group of scientists analyzed the lost moon tapes until they have the answer.

The source of the bizarre moon warming in the 1970s was no other than the Apollo astronauts themselves.

40-Year-Old Moon Mystery Solved

According to the analysis published in the Journal of Geophysical Research: Planets, the astronauts of the Apollo missions disturbed the moon's surface when they walked and drove a rover on it. The astronauts' activity resulted to the moon reflecting less of the sun's light back out to space. This raised the moon temperature by 1 to 2 degrees Celsius or 1.8 to 3.6 degrees Fahrenheit.

"In the process of installing the instruments you may actually end up disturbing the surface thermal environment of the place where you want to make some measurements," explained Seiichi Nagihara, the lead author of the study and a planetary scientist at Texas Tech University in Lubbock, Texas.

Most importantly, however, the analysis highlighted that human missions to the moon will always, at all times, disturb its natural environment. Any deployment of instruments or astronauts will always impact and change the natural surroundings of the moon.

The scientists highlighted that this insight is valuable in carefully planning future lunar missions, particularly the technology that people will be bringing to the moon.

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