In the 1971 NASA photo above, Apollo 15 lunar module pilot Jim Irwin loads the lunar rover with tools and equipment in preparation for the first lunar spacewalk at the Hadley-Apennine landing site. The Apollo 15 launched on July 26, 1971, from Launch Pad 39A at the Kennedy Space Center.

(NASA)

At a Glance

After nearly 40 years, researchers have found missing tapes from NASA's Apollo 15 mission. Data from the tapes suggest astronauts caused the moon's surface to heat up after they kicked around the planet's dust.

NASA tapes that were missing for almost 40 years may have revealed what caused the surface of the moon to heat up right after flags were planted by the first astronauts.

A team of researchers managed to t (HFE) that were “lost” due to an archiving error. They used the recovered data collected between January 1975 and September 1977 to piece together clues in the mystery behind the lunar heatwave.

According to their findings, the uptick in the moon’s surface temperature was likely caused by the astronauts kicking up too much dust.

The astronauts that traveled to the moon between 1969 and 1972 kicked up so much moon dust that , LiveScience reports. In just six years, this soil took in enough radiation from the sun to heat the moon’s surface by up to 3.6 degrees.

(MORE: )

", where they walked,"study co-author and Lunar and Planetary Institute senior staff scientist WalterKiefer told CBC.com. "And we can see where they scuffed dirt up—and what it leaves behind is a darker path."

"In other words, the astronauts walking on the moon changed the structure of the regolith,” Keifer explained, referring to the loose layer of debris found on the surface of the moon.

Additionally, the probes placed closer to the surface picked up higher temperatures than those stuck further down, which suggests the rise in heat began at the surface and not within the planet, according to the scientists.

Photos captured by the Lunar Reconnaissance Orbiter Camera showed spots near the landing sites of the Apollo thathad become covered with streaks where astronauts either walked or drove across the moon’s surface, causing dust to move around, LiveScience reports. The researchers believe the moonwalkers’ activity threw off the measurements of the probes by changing the environment surrounding them.

“In the process of installing the instruments, you may actually end up ," study co-author and Texas Tech University planetary scientist Seiichi Nagihara told the American Geophysical Union. "That kind of consideration certainly goes into the designing of the next generation of instruments that will be someday deployed on the moon."

The researchers discovered the tapes at the Washington National Records Center located in Suitland, Maryland. However, the data only accounts for roughly three months of the temperature records from 1975, LiveScience reports. In order to fill in the gaps of the missing information, the scientists used information from hundreds of the Lunar Planetary Institute’s weekly performance logs.