Universe Today’s Bob King reports on suggestions that the Moon might have been volcanically active to geologically very recent times, perhaps even only 50 million years ago.
The deposits are scattered across the Moon’s dark volcanic plains (lunar “seas”) and are characterized by a mixture of smooth, rounded, shallow mounds next to patches of rough, blocky terrain. Because of this combination of textures, the researchers refer to these unusual areas as “irregular mare patches.”
Measuring less than one-third mile (1/2 km) across, almost all are too small to see from Earth with the exception of Ina Caldera, a 2-mile-long D-shaped patch where blobs of older, crater-pitted lunar crust (darker blobs) rise some 250 feet above the younger, rubbly surface like melted cheese on pizza.
Ina was thought to be a one-of-a-kind until researchers from Arizona State University in Tempe and Westfälische Wilhelms-Universität Münster in Germany spotted 70 more patches in close-up photos taken by the LRO. The large number and the fact that the patches are scattered all over the nearside of the Moon means that volcanic activity was not only recent but widespread.
Astronomers estimate ages for features on the moon by counting crater numbers and sizes (the fewer seen, the younger the surface) and the steepness of the slopes running from the tops of the smoother domes to the rough terrain below (the steeper, the younger).
“Based on a technique that links such crater measurements to the ages of Apollo and Luna samples, three of the irregular mare patches are thought to be less than 100 million years old, and perhaps less than 50 million years old in the case of Ina,” according to the NASA press release.