Astronomers are moonstruck! The man in the moon, we learned just last week, formed from dark flowing lava over three billion years ago, instead of a long supposed giant asteroid impact. Now, we learn that same volcanism may have kept on erupting until surprisingly recent times.
A new discovery by a group of geologists at Arizona State University’s School of Earth and Space Exploration shows that the moon has seen small but widespread eruptions of basaltic lava during the last 50 million years, a geologically recent period.
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; the others are Julie Stopar, Samuel Lawrence and Mark Robinson, all researchers in the school, and Carolyn van der Bogert and Harald Hiesinger of the Westfälische Wilhelms-Universität Münster in Germany.
If confirmed, the finding could suggest the presence of radioactive elements keeping the moon’s insides warm.
Using high-resolution images from Nasa’s Lunar Reconnaissance Orbiter spacecraft, they identified 70 small volcanic features scattered across the moon’s dark volcanic plains, or maria.
A combination of smooth, low, rounded mounds near patches of rough, blocky terrain, the features are referred to by scientists as irregular mare patches.
The ages of the irregular mare patch features come from studies of crater sizes and numbers within a given area. The results show that lunar volcanism ended gradually, continuing until less than 50 million years ago.
“The existence and young age of the irregular mare patches provides a new constraint for models of the lunar interior’s thermal evolution,” Sarah Braden, the lead author said.
“The lunar mantle had to remain hot enough for long enough to provide magma for the small-volume eruptions.”
The features are too small to be seen from Earth, averaging less than a third of a mile (500 meters) across their largest dimension. One feature named Ina has been known for a long time, having been imaged from lunar orbit by Apollo 15 astronauts in the 1970s. Several early studies indicated that Ina could be very young (10 million years or less), but only a few irregular mare patches were known then, and their significance was unclear.
The large number of these features and their wide distribution strongly suggest that late-stage volcanic activity was not an anomaly but an important part of the moon’s geologic history. The numbers and sizes of the craters within these areas indicate the deposits are relatively recent.
‘These young volcanic features are prime targets for future exploration, both robotic and human,’ said Mark Robinson, LROC principal investigator at Arizona State University. The discovery gives the moon’s volcanic history a new chapter. As Braden says, “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.”
“This finding is the kind of science that is literally going to make geologists rewrite the textbooks about the moon,” said John Keller, a project scientist at NASA.