Evrim Yazgin
Cosmos science journalist
A new study suggests that, beneath its cold and dormant exterior, the moon is more dynamic than previously thought.
“Knowing that the moon is still geologically dynamic has very real implications for where we’re planning to put our astronauts, equipment and infrastructure on the moon,” says Jaclyn Clark, an assistant research scientist at the University of Maryland in the US.
Scientists have been examining the moon’s surface in detail for decades. Evidence from dark, flat areas filled with solidified lava called lunar maria has previously revealed that the moon’s surface experienced significant compression in its distant past. Large, arching ridges on the surface were caused by contractions billions of years ago.
The moon has been geologically dormant, or “dead”, ever since. Or so we thought.
A study led by senior author Clark and published in the Planetary Science Journal challenges this and suggests that, beneath the surface, the moon might still be quite active.
The ridges on the far side of the moon are notably younger than those on its near side, the researchers found. This suggests subsurface dynamics much more recently than expected.
“Many scientists believe that most of the moon’s geological movements happened 2.5, maybe 3 billion years ago,” says Clark.
“But we’re seeing that these tectonic landforms have been recently active in the last billion years and may still be active today.
“These small ridges seem to have formed within the last 200 million years or so, which is relatively recent considering the moon’s timescale.”
Advanced mapping techniques revealed 266 previously unknown small ridges on the moon’s far side. The ridges were spotted using data from NASA’s Lunar Reconnaissance Orbiter.
The ridges appeared in groups of 10–40 in volcanic regions that likely formed 3.2–3.6 billion years ago.
To estimate the age of these small ridges, the researchers used a technique called crater counting. Newer areas on a planetary body’s surface tend to have fewer craters than old ones.
“After counting the craters around these small ridges and seeing that some of the ridges cut through existing impact craters, we believe these landforms were tectonically active in the last 160 million years,” Clark explains.
Though much younger, Clark’s team found that the ridges on the far side were similar in structure to the ones on the near side, suggesting that they were formed by the same forces.
“We hope that future missions to the moon will include tools like ground penetrating radar so researchers can better understand the structures beneath the lunar surface,” Clark adds.
