Astronauts caused global warming on the Moon

Walking and driving rovers kicked up dust, exposing dark, heat-absorbing lunar regions.
By Laurel Kornfeld | Oct 01, 2018
The 12 NASA astronauts who walked on the lunar surface between 1969 and 1972 caused the Moon to warm by four degrees Fahrenheit (two degrees Celsius), according to more than 400 reels of NASA tape that were found after having been lost for nearly 40 years.

A research team unearthed 440 reels of Apollo mission tapes housed at the Washington National Records Center in Suitland, Maryland.

Temperature probes placed on the lunar surface by astronauts on the 1971 Apollo 15 and 1972 Apollo 17 mission recorded and transmitted data back to NASA's Johnson Space Center (JSC) in Houston, Texas, until 1977. Yet for unknown reasons, only the first three years of that data was archived at the National Space Science Data Center.

Texas Tech University (TTU) planetary scientist Seiichi Nagihara, who led the eight-year search for the missing data, believed it contained answers to the mysterious lunar warming.

After restoring and analyzing the tapes, Nagihara's team concluded that the astronauts' walks on the lunar surface kicked up a high level of dust, exposing huge regions of dark material that then absorbed solar radiation, causing the warming.

"You can actually see the astronauts' tracks, where they walked. And we can see...where they scuffed dirt up--and what it leaves behind is a darker path," said Lunar and Planetary Institute senior staff scientist Walter Kiefer.

The newly exposed dark regions on the Moon's surface, which had not been exposed to sunlight for several billion years, absorbed enough heat to raise the global lunar temperature by as much as 3.6 degrees Fahrenheit (two degrees Celsius) in just six years.

"In other words, the astronauts walking on the Moon changed the structure of the regolith," Kiefer explained.

To supplement data from the tapes, the researchers also reviewed weekly logs of the Lunar and Planetary Institute, which filled in gaps where data was missing, especially for Apollo data collected between 1973 and 1977.

They also looked at photos taken by the camera on the Lunar Reconnaissance Orbiter (LRO), which revealed dark streaks at the Apollo sites where astronauts walked and drove rovers.

Among their discoveries is the fact that probes put down near the lunar surface recorded a steeper and faster temperature increase than those placed deeper below the surface. This indicates the lunar warming originated at the Moon's surface and not from its interior.

Ironically, the act of installing the probes itself could have changed the surface environment around them, inadvertently throwing off their measurements.

Knowing this can occur will impact the design of future lunar surface probes, Nagihara told the American Geophysical Union (AGU).

A paper on the study has been published in the Journal of Geophysical Research: Planets.



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