Fresh evidence of 'late-stage' volcanic activities may rewrite history of moon

NASA's Lunar Reconnaissance Orbiter (LRO) has provided researchers evidence of late-stage volcanic activities in Moon's geologic history. Scores of distinctive rock deposits observed by LRO were estimated to be less than 100 million years old. Some areas could be less than 50 million years old. The steep slopes leading down from the smooth rock layers to the rough terrain are consistent with the young age estimates.

The deposits are scattered across the Moon's dark volcanic plains 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.

One of the largest, well-studied areas was called Ina, imaged from lunar orbit by Apollo 15 astronauts. John Keller, LRO project scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland said that the large number of these features and their wide distribution strongly suggested that late-stage volcanic activity was not an anomaly but an important part of the Moon's geologic history.

In contrast, the volcanic plains surrounding these distinctive regions are attributed to volcanic activity that started about 3 1/2 billion years ago and ended roughly 1 billion years ago. At that point, all volcanic activity on the Moon was thought to cease.

Several earlier studies suggested that Ina was quite young and might have formed due to localized volcanic activity. However, in the absence of other similar features, Ina was not considered an indication of widespread volcanism.

The paper was published in Nature Geoscience.