The lost data tapes recovered by the scientists helped pinpoint the source of the warming during Apollo missions
With the help of missing moon tapes, researchers have uncovered the culprit behind a strange shift in temperatures during Apollo missions.
When astronauts on Apollo 15 and 17 missions arrived at lunar surface, they used instruments to retrieve samples and measured moon’s subsurface temperature. To their surprise, the subsurface temperature of the moon was warmer than expected. The major question was: How did the moon’s subsurface temperature increased during those missions.
Apollo probes measured lunar temperatures from 1971 to 1977 and recorded the data on open-reel magnetic tapes. But when the experiments ended, only tapes NASA received were from 1971 to 1974. The rest of the tapes were never archived and presumably lost somewhere.
Scientists have long debated over the reason for this warming. Some suspected it was due to the astronauts’ activity, while others thought it could have been due to changes in the moon’s orbit. Now researchers say they have figured out the actual cause of this shift. They believe that astronauts disturbed the moon’s surface soil by walking and driving a rover on it. As a result, the moon reflected less amount of sunlight back into the space, which in turn raised the lunar surface temperature by 1-2 degrees Celsius.
“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,” said lead author Seiichi Nagihara, a planetary scientist at Texas Tech University in Lubbock, Texas. “That kind of consideration certainly goes in to the designing of the next generation of instruments that will be someday deployed on the moon.”
Researchers came to this conclusion after recovering the decades-old lost heat flow data. In 2010, they started searching for missing data and found that NASA actually had a separate set of tapes specifically for archiving. Those 440 archival tapes had data from April through June 1975 and it was stored in Washington National Records Center in Suitland, Maryland. Moreover, they recovered hundreds of weekly logs at the Lunar and Planetary Institute in Houston that recorded temperature readings from the heat flow probes from 1973 through 1977.
It took the researchers several years to extract data from these old tapes and to analyze their contents. However, the information on missing tapes and the weekly performance logs was enough to draw a conclusion. Researchers found that temperatures measured close to moon’s surface were higher than the few meters down into its subsurface, suggesting the heat started from the surface and moved downward. The images of the moon’s surface from the Lunar Reconnaissance Orbiter also suggested that astronauts’ activity disturbed the surface environment at their landing sites and led to a darker lunar soil in those areas.
“It doesn’t take much disturbance to get that very subtle warming on the surface,” said Nagihara. “So analysis of the historic data together with the new images of the moon really helped us characterize how the surface warmed.”