Apollo Moon sample opened after 50 years contains evidence of extraterrestrial landslide

More than 50 years after the last manned Moon mission, the Apollo programme is still making groundbreaking discoveries.

Lunar rock collected by Apollo 17 is revealing more about the Light Mantle, a distinctive bright streak across the Moon’s surface. It’s believed to be the remains of an ancient landslide that happened in the distant past, but the exact cause is unknown.

Asteroid strikes, debris from a nearby mountain and seismic activity are all possibilities, but orbital photographs can only reveal so much. Scientists are now studying a rock core from Apollo 17 that was recently unsealed for the first time in 50 years, allowing new insights into the geology of the area.

The new research was led by our scientist Dr Giulia Magnarini, who studies the geology of the Moon and other extraterrestrial bodies. She says that ongoing research into Apollo samples is helping to prepare for humans returning to the Moon in the near future.

“This research is a way of continuing the legacy of the Apollo missions more than 50 years later, providing a bridge to the planned Artemis programme,” explains Giulia.

“We’ve learned so many lessons from these samples about how to preserve, store and open lunar material without damaging the contents. This is already feeding into plans for Artemis’ science and helping to develop new instruments.”

The findings of the study were published in the Journal of Geophysical Research: Planets.

Science on Apollo 17

After launching in 1972, Apollo 17 was the last of the Apollo programme missions. But it was also a mission of firsts. It set records for the amount of time orbiting the Moon, while a group of five mice became the first rodents to enter lunar orbit as part of an investigation into the impacts of cosmic rays.

More notably, however, was that Apollo 17 took the first scientist to the Moon. Previous astronauts had been trained to carry out research, but lunar module pilot Harrison Schmitt had a doctorate in geology which helped him and fellow astronaut Eugene Cernan to study the Moon’s rocks.

The Light Mantle was one of the key targets of the mission. The five-kilometre-long deposit, which lies at the base of the two-kilometre-high South Massif mountain, has fascinated scientists ever since it was first found.

“I have been studying long runout landslides on Earth and Mars, but the Light Mantle is currently the only one we know of on the Moon,” Giulia says. “We don’t know how these long runout landslides formed or what allowed them to run for several kilometres.”

Cores were drilled down into the Light Mantle and sealed, becoming part of the 110.5 kilogrammes of Moon rock that Apollo 17 brought back to Earth. This was more than any other Apollo mission, and while some was studied at the time, a significant amount was stored for the future.

“NASA were really forward-thinking during the Apollo mission to put some samples aside,” adds Giulia. “They were stored so that they could be studied using more advanced technology and new scientific approaches that hadn’t even been thought of at the time.”

“When the samples were originally brought back, scanning technology wasn’t that detailed. Now, with micro-CT scanning, we have medical-level scans that allow us to investigate these samples in fine detail.”

Lunar landslides

Using scans taken of the NASA sample, Giulia and the team analysed its contents at our Imaging and Analysis centre. They were particularly interested in examining its clasts, which are fragments that broke off from the slope of the South Massif during the landslide.

The team’s previous research had simulated how landslides on the Moon might work using rock of a similar composition. Now, they got to compare their computer results to the contents of the core sample to see if their simulations reflected reality.

“The clasts tell us a lot about the process of the landslide itself and how the material within it has been transported,” Giulia explains. “We saw that the finer material coating the clasts in the core comes from the clast and not the surrounding debris, suggesting that the clasts broke up and helped the landslide to flow more like a fluid.”

While it’s still uncertain what triggered the landslide in the first place, one possibility is that it was caused by the asteroid strike that formed the Moon’s large Tycho crater. During the impact, countless tonnes of Moon rock would have been thrown upwards and scattered over thousands of kilometres.

As this debris hit the ground, it would have formed small craters of its own. These secondary craters can be seen radiating out of Tycho, including some which run in the direction of the South Massif and the Light Mantle.

“It’s been suggested that some of the material thrown up by the creation of Tycho might have struck the South Massif,” Giulia explains. “This could have triggered the landslide which ultimately formed the Light Mantle.”

“We’re currently investigating this possibility as part of ongoing research into the Moon’s geological history.”