Alive and Kicking

Beneath its cold, dormant exterior, the Moon is much more active than previously thought.

Studies have shown that the Moon’s lunar maria – those dark and flat areas filled with solidified lava – underwent significant compression in processes that ended billions of years ago.

These contractions created large, arching ridges on the near side of the Moon between 2.5 and 3 billion years ago, and scientists had believed the surface was dormant ever since.

However, a new study published in the Planetary Science Journal found that the ridges of the Moon’s far side are much younger than those on the near side, suggesting that the Moon’s surface has been active within the last 200 million years and might still be active today.

Through advanced mapping and modeling techniques, the researchers found 266 ridges on the Moon’s far side that had previously gone unnoticed.

The Moon’s ridges generally appeared in groups of 10 to 40 in certain volcanic regions estimated to be as old as 3.6 billion years. These areas are where the Moon’s surface tends to be weak, the researchers explained in a statement.

To estimate how old the ridges are, the team used a technique called crater counting.

“Essentially, the more craters a surface has, the older it is,” assistant researcher Jaclyn Clark explained.

By counting the craters around the ridges and observing that some of the ridges cut through existing craters, the researchers concluded that the Moon was tectonically active in the past 160 million years – that’s relatively recent considering the Moon is about 4.5 billion years old.

The far-side and near-side ridges are similar in structure, suggesting that they were likely created by the same forces, namely shifts in the lunar orbit and the Moon’s gradual shrinking due to its core cooling down, caused the Moon’s crust to crack in a way that resembles the seismic activity detected by the Apollo missions to Earth’s biggest satellite decades ago.

This discovery could impact the logistics of future missions because knowing that the Moon is still geologically active will influence where to place astronauts, equipment, and infrastructure on its surface.