It’s no secret that the Moon has experienced many volcanic eruptions in its 4.5-billion-year history. After all, its landscape is covered with hardened lava flows that make up many of its well-known features.
However, scientists had long believed that the most recent volcanic activity on the Moon occurred around a billion years ago. That all changed in 2014, thanks to high-resolution images captured by NASA’s Lunar Reconnaissance Orbiter (LRO) and a team of researchers from Arizona State University led by planetary scientist Sarah Braden.
The first hint of relatively recent volcanic activity on the Moon came from the Apollo 15 mission in 1971, when astronauts photographed an odd lunar feature known as Ina that resembled the aftermath of a “fresh” volcanic eruption. For decades, Ina was considered a unique lunar oddity until researchers began studying the LRO images. They found over 70 similar landscapes, known as Irregular Mare Patches (IMPs), which appear to be the remnants of lunar lava flows.
Scientists can estimate the age of landscapes on the Moon from the presence of craters caused by a steady stream of meteoroids impacting its surface. The more craters a particular landscape contains, the older it is. The LRO images reveal that some IMPs are very lightly cratered, suggesting they are no more than 100 million years old. Some may be as "young" as 50 million years old.
This may sound like a long time ago, but geologically, it’s barely an instant. For comparison, 100 million years ago was the height of the Cretaceous period, when dinosaurs roamed our planet. Fifty million years ago, primates were already in existence on Earth.
Mapping the Moon:
- The Lunar Reconnaissance Orbiter has been orbiting the Moon since 2009. Since then, it has mapped over 98% of the lunar surface at 100-meter resolution. In addition to its wide-angle camera, it has two narrow-angle cameras for extreme closeups at 1.6 ft (0.5 m) per pixel.
- LRO data is considered essential for planning future NASA missions to the Moon, including those with a human presence. It has helped to map possible landing sites, suggested the location of resources, taken radiation readings, and tested new technologies.
- If there really was lunar volcanic activity as recently as 50–100 million years ago, as the LRO images suggest, it could mean the interior of the Moon is much hotter than previously thought.