Leonard David's INSIDE OUTER SPACE

One of many newly-discovered young volcanic deposits on the Moon (4.330°N, 33.750°E), this example is near the crater Maskelyne. The direction of sunlight is from the right and north is up.
Credit: NASA/GSFC/Arizona State University

The Earth’s own Moon never fails to disappoint.

New data made possible by the NASA Lunar Reconnaissance Orbiter (LRO) spacecraft has identified many young volcanic deposits.

A new paper, published in Nature Geoscience, presents 70 topographic anomalies, informally called Irregular Mare Patches, or IMPs. Furthermore, most of these occurrences were previously undocumented.

The new discovery has been made by a group of geologists at Arizona State University’s School of Earth and Space Exploration (SESE) and shows that the Moon has seen small, but widespread eruptions of basaltic lava during the last 50 million years. That’s a geologically recent period.

According to co-author Mark Robinson, the principal investigator for the LRO Camera (LROC) on NASA’s Lunar Reconnaissance Orbiter spacecraft:

“Their sharp nature and general lack of impact craters greater than 20 meters in diameter indicate these deposits probably formed in the last 100 million years, perhaps even more recently than 50 million years ago. An amazing result!”

Changing the way we think

Robinson also noted that the images are changing the way we think about the Moon.

“Not only are the IMPs striking landscapes, they also tell us something very important about the thermal evolution of the Moon,” Robinson said on the LROC website.

“The nearside has extensive mare basalt flows covering much of its surface, however we know from analysis of Apollo samples and crater counts that the bulk of lunar volcanism occurred from 3.9 to 3.1 billion years ago, and shut-off sometime around 1billion years ago,” Robinson said. “However the IMPs seemed to have formed significantly after the canonical cessation of lunar mare basalt volcanism indicating the interior of the Moon is perhaps hotter than previously thought.”

Apollo 15 astronaut Dave Scott deploying heat flow probe.
Credit: NASA

Future lunar exploration

Lastly, the IMPs are a fascinating part of the story of lunar volcanism over time, and now they must be considered high priority targets for future exploration, Robinson added.

“A sample return mission from one of these enigmatic deposits would tell us so much about the Moon as a whole. When did these lavas erupt? Is their chemistry different than the basalts returned by the Apollo astronauts? Is it likely that volcanic eruptions may occur at some point in the future? A highly accurate age date for the IMPs would also serve as a much needed calibration point for the lunar cratering chronology,” Robinson said.

Understanding the IMPs is a “crucial improvement” not only for studying and understanding the Moon, but also for Mars and Mercury investigations, Robinson added.

Sarah Braden, a recent SESE graduate, is the lead author; the others are Julie Stopar, Samuel Lawrence, and Mark Robinson (all of SESE) and Carolyn van der Bogert and Harald Hiesinger of the Westfälische Wilhelms-Universität Münster in Germany.

For a sweeping review of the new evidence for young lunar volcanism, go to:

http://lroc.sese.asu.edu/posts/818

The full paper in Nature Geoscience is available here:

http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2252.html

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