Volcanoes Erupted On The Moon Within The Past 100 Million Years

On the cosmic timeline, that’s basically yesterday.

Ina

The smooth and rough terrain of InaNASA/GSFC/Arizona State University

Our cold, lifeless Moon just turned the corner into pretty hot and tempting. It turns out Earth’s satellite was once rife with volcanic activity, and some of its eruptions occurred within the past 100 million years – perhaps even within the past 50 million years. That’s about a billion years earlier than what researchers had originally assumed.

The discovery reveals that the Moon is still somewhat warm, containing more heat than previously believed. This news may alter the perceived timeline of the Moon’s thermal evolution, changing what we know about its origins and how it formed over time.

In a new study published in the journal Nature Geoscience, researchers from Arizona State University analyzed landforms on the Moon's surface using images from NASA's Lunar Reconnaissance Orbiter (LRO), a satellite that has been orbiting the Moon since 2009. Through their analysis, the researchers discovered up to 70 topographic anomalies called Irregular Mare Patches, or IMPs. IMPs are weird formations in the lunar maria, or basaltic plains on the Moon's surface. They're thought to be leftover remnants of small volcanic eruptions.

An Array Of IMPs

Red circles indicate either a single IMP or a cluster of smaller IMPs.NASA/GSFC/Arizona State University

Originally, the researchers had wanted to learn more about one IMP in particular called Ina. The landform was first spotted by Apollo 15 in 1971 and has been somewhat of an enigma for decades. Ina exhibited two distinct textures: smooth deposits mixed with more rough-looking deposits. Researchers believed that the smooth areas are likely old lava flows covering portions of the rougher terrain.

Ina was unlike anything ever before seen on the Moon’s surface. Early investigations revealed that the landform was once a collapsed volcanic vent, and that it was much younger than the surrounding region.

But after looking at the LRO images, the researchers found that Ina isn't one-of-a-kind after all. The high-resolution satellite images revealed 70 additional IMPs on the nearside of the Moon, indicating multiple regions that had once been home to volcanic activity. The IMPs range in size from 100 meters to 5,000 meters across, and they have the same dual-texture terrain observed in Ina. Sarah Braden, a lead author on the study, tells Science that these landforms are signatures of low-lying shield volcanoes that oozed "soupy lava."

To determine the age of these IMPs, the researchers measured the number of impact craters on the smooth regions of the landforms. The idea is that the greater number of craters, the older the surface, becauase young surfaces wouldn’t have as much time to be pelted by outside space objects. The crater distribution on three of the largest IMPs indicated an age younger than 100 million years. Ina turned out to be very young, possibly only 33 million years old.

Many researchers believed that lunar volcanism occurred about 3.9 to 3.1 billion years ago and ended abruptly about 1 billion years ago. This latest research throws a huge wrench into that timeline. The IMPs also pose a great target for future space exploration. Just a few samples from these landforms could tell us a lot about our Moon’s origins and overall life.

Ina Closeup

A closeup portion of Ina. Don't be confused: The smooth portions actually set on top of the rough terrain. The direction of the Sun makes an illusion of inverted topography.NASA/GSFC/Arizona State University