The moon may enter a new geological period thanks to human activity

Humanity’s influence on the moon is so great that we should define a new geological epoch, just as we are doing so on Earth with the creation of the Anthropocene, researchers argue. We should also create lunar “national parks” to preserve areas for scientific study, they say.

The Anthropocene is the name given to the epoch in which humans began having a significant impact on Earth’s geology and ecosystems. The definition is still being agreed upon, but most researchers suggest Earth entered this period in 1950, marked by the presence of plutonium isotopes from nuclear weapons tests in sediment at the bottom of a relatively untouched lake in Canada.

Now Justin Allen Holcomb at the University of Kansas and his colleagues say the moon has also entered its own Anthropocene, as the effect of spacecraft landings, lunar rovers and human activity displace more surface regolith than natural processes such as meteoroid impacts. 

Humans began having an effect on the moon in September 1959 when the Soviet Union crash-landed its Luna 2 probe on the surface, leaving a crater. India became the fourth country to make a soft landing on the moon this year, and a range of national and private missions are planned in the next few years. To date, we have caused surface disturbances in at least 59 locations on the moon’s surface, and discarded objects including spacecraft components, bags of human excrement, flags and golf balls.

Holcomb says that there is a lot of variation in estimates of the weight of human-made objects left on the moon, and the amount of regolith displaced by human activity, but that both are likely to drastically increase in coming years as colonisation and mining begins – and that this demands a discussion on the repercussions.

“It’s just so focused on the amount of money or minerals we can get, but we really do need to slow down and talk about what the consequences are,” he says. “And I think other fields of science like anthropology, ecology, archaeology, should be involved in these discussions too.”

Ingo Waldmann at University College London says the moon has certainly entered the Anthropocene as lunar geology is not very dramatic; weak lunar quakes happen sporadically, and water is deposited in the surface regolith by solar winds only over aeons.

“It’s extremely slow,” he says. “There might be an [asteroid] impact once once every couple of million years or so. But apart from that, not much happens. Just us walking on it has a bigger environmental impact than anything that would happen to the moon in hundreds of thousands of years.” The current lunar geological division, the Copernican period, dates back to more than a billion years ago. By contrast, Earth has passed through around 15 geological periods in this time.

Waldmann is concerned that missions such as as NASA’s Artemis III, which aims to put astronauts on moon for the first time since Apollo 17 in 1972, will contaminate the lunar surface and make understanding its geology more difficult. He says there should be an international agreement for the creation of the equivalent of a “national park” on the moon.

“The lunar surface is the most pristine environment that we have access to, because the regolith builds up so slowly and erosion happens so slowly, that you do have the whole imprint of the solar system on the moon as geological records, which we don’t have on the Earth. I think it is important for science.”

Mark Sephton at Imperial College London supports the proposal, but says a balance is needed. “You want to at least have the equivalents of national parks that can be used in the future for deep interrogation and exploration, to understand the history of the moon,” he says. “But at the same time, human beings need to explore and move out into the solar system.”