Astronauts' movement increased subsurface temperatures on the moon, study finds

It may have been one giant leap for man, but those steps may have consequences for mankind.

The presence of astronauts on the moon caused an unexpected warming ofits subsurface temperatures for a period of time in the 1970s, a new study has foundafter delving into"lost" tapes from the Apollo missions.

In 1971 and 1972,NASA deployed sensors on the moon during the Apollo 15 and 17missions in an effort to measure the moon's surface and subsurface temperatures a project dubbed the heat flow experiment.

Data was collected and beamed back down to Earth until 1977, where scientists were baffled by the gradual warming of the moon's surface being read by the sensors.

NASA ultimately abandoned the research due to a lack of funding, and only some of the tapes were archived, with the others assumed lost, leaving scientistsunable to analyze it further.

But thosemissingtapes were found recentlyin the National Archives, said study co-author WalterKiefer, a senior staff scientist at the Lunar and Planetary Institute. He and his team spent years recovering and interpreting the datain order to pinpoint the source of the warming.

Specifically, the decades-old data showed the moon's subsurface temperatures in some areas as deep as three metres increased from 1.6 C to 3.5 C over the roughly six-year period measurements were being taken.

Bright vs. dark

The moon consists primarily of two different types of rock:anorthositeand basalt.Anorthositeis light in colour andmakes the moon bright, whilebasalt, which is common on Earth, is darker andappears as the maria, or "seas," on the moon.

Lighter-coloured surfaces reflect more energy outward, while darker surfaces absorbenergy.

Using photos from the extremely high-resolution camera aboard the Lunar Reconnaissance Orbiter (LRO) orbiting the moon, the scientists determined that as astronauts walked or droveon the moon, it disturbed the anorthositelunar soil also known asregolith left over from billions of years of bombardment from space rocks.

That disruptionexposed the darker soil, which thenabsorbed more of the sun's energyand ultimatelyraised the moon's temperatures.

"You can actually see the astronauts tracks, where they walked,"Kiefersaid. "And we can see where they scuffed dirt upand what it leaves behind is a darker path. In other words, the astronauts walking on the moon changed the structure of the regolith in such a way that made it a little bit darker."

Over years, that energy propagated downward anddeeper into the lunar surface, which is what appeared on the newly acquired data record.

Eventuallythe temperatures would have reached an equilibrium asabsorptionstopped, said Kiefer, notingit may have already happened.

Since Neil Armstrong took those historic first steps on July 20, 1969, 11 others have walked on the moon.

Future visits

The findings are a reminder of how human activity can disrupt a system that has been in isolation for billions of years, Kiefer said, which could provide valuable information forfuture lunarand potentially Marsmissions.

"The overall effect on the moon of having even a few hundred peopleisn't going to be that big of a deal,"Kiefersaid. "The moon will be just fine if it's two degrees hotter than it is right now."

While a slight change to moon's temperature might not pose a problem, the findingsshould affect our scientific understanding of our nearest neighbour and the evolution of the solar system as a whole, says planetary scientist CatherineNeish.

"Even on Earth, it's this balance of making progress with science and technology but respecting the system that we were given as human beings," said Neish, who works atWestern University in London, Ont.

"We're obviously changing Earth in significant ways, and I'm sure we would do that on other planets as well."

And while there's no lifeon the moon, Neish said human disruption isstill alteringa pristine environment that contains history and potential clues to the origin of life on Earth.

"Should we morally be concerned about that?" she said. "We are affecting nature in a very substantial wayand we're making questions that we want to answer about the fundamental properties of the universe more difficult to answer."