New data from NASA’s Lunar Reconnaissance Orbiter (LRO) suggests recent volcanic activity on the surface of the moon. Some lunar eruptions were as recent as 33 million years ago. Now 33 million years may not sound very “recent” to us but on a geologic time scale it’s like it happened just last week.
That is a clear departure from the widely believed view that the moon’s volcanoes went cold quite a while back — between 1 and 1.5 billion years ago.
The discovery was announced in a paper published online Oct. 12 in Nature Geoscience. Sarah Braden, a recent School of Earth and Space Exploration graduate, is the lead author of the study. Her colleagues include Julie Stopar, Samuel Lawrence and Mark Robinson, all researchers at the school, and Carolyn van der Bogert and Harald Hiesinger of the Westfälische Wilhelms-Universität Münster in Germany.
The team was able to identify 70 small volcanic features scattered across the moon’s dark volcanic plains, or maria, according to an Arizona State University press release. The features show as a combination of smooth, low, rounded mounds near patches of rough, blocky terrain. The scientists refer to these unusual areas as irregular mare patches.
Small areas of what appear to be recent basaltic lava deposits have been identified in images acquired by the Lunar Reconnaissance Orbiter Camera (LROC) on the moon’s near side. These “irregular mare patches,” or IMPs, contain rough and smooth surfaces with few craters larger than 20 meters (65 feet), indicating a young age.
70 IMPs have thus far been identified, the best-known of which (and first discovered) is one named Ina, seen by Apollo 15 from lunar orbit. 2 km (1.25 miles) across, Ina was unlike any other region seen by Apollo astronauts and was originally thought to be an irregularly-collapsed caldera.
Now, after five years of observations by LRO, scientists know that Ina is not just a singular anomaly but rather one of many IMPs that point to a much longer span of lunar volcanism — and possibly a warmer lunar interior — than what had previously been estimated.
“This finding is the kind of science that is literally going to make geologists rewrite the textbooks about the moon,” said John Keller, LRO project scientist at NASA’s Goddard Space Flight Center.
“The existence and young age of the irregular mare patches provides a new constraint for models of the lunar interior’s thermal evolution,” Braden says. “The lunar mantle had to remain hot enough for long enough to provide magma for the small-volume eruptions.”
Robinson added that the discovery is hard to reconcile with what’s currently believed about the temperature of the moon’s interior. “These young volcanic features are now prime targets for future exploration, both robotic and human,” he said, according to the automaker.
The discovery gives the moon’s volcanic history a new chapter.
“Our understanding of the moon is drastically changed by the evidence for volcanic eruptions at ages much younger than previously thought possible, and in multiple locations across the lunar maria,” said Braden.