First moon samples in more than 40 years could change lunar history

At the end of 2020, a Chinese space capsule delivered fresh moon samples to Earth for the first time in about four decades, and these precious moon rocks have just revealed a new detail about our planet’s luminous companion: its volcanoes were alive and active. much longer than scientists thought. .

“All of our experience tells us that the moon should be cold and dead 2 billion years ago. But it isn’t, and the question is, ‘Why? “” said Alexander Nemchin, professor of geology at Curtin University of Australia and author of the analysis published Thursday in the journal Science.

Along with a large international team of researchers, Nemchin discovered that some of the newly transported moon rocks contain lunar fragments from the last days of the white orb’s timeline. Dated about two eons ago, these fragments are relatively young. But here’s the kicker: those same pieces are also remnants of a volcanic eruption.

As they connected the dots, the team members realized they were looking for some solid confirmation that the lunar surface was alive quite late in the game.

“We have to dig deeper with this,” Nemchin remarked. “We stress that our current views need a readjustment – further research will tell how dramatic this readjustment should be.”

Welcome back, lunar research

The saga began last year in December, when China’s Chang’e 5 mission sent a spacecraft to scrape the moon’s surface and collect a variety of rock and dust samples for Earth-based analysis. . He returned with about 4 pounds (2 kilograms) of alien material.

The year 1976 marks the last time lunar samples were brought back to our home planet, an accomplishment of the Soviet Union’s Luna 24 mission. But before that, NASA’s Apollo missions traveled the route from Earth to the Moon several times – the Crusades rendered photographs, moon stones and personal anecdotes from astronauts.

“There was a need and a will to do it 50 years ago,” Nemchin explained. “Then, priorities have changed and everyone moved on. But now, he said, “we again have the moon at the center of our concerns. “

He notes that lunar research is important not only from an astronomical standpoint, but also because any effort to get to the moon – or really, all space exploration – tends to accelerate technologies that ultimately benefit us on Earth. .

An example of such a fortuitous technology comes from the research of Australian physicists in the 90s. They developed a very complex mathematical tool in the hope of detecting spread signals from black holes that have disappeared in the cosmos. Unfortunately, they never found one, but their invention paved the way for modern Wi-Fi.

Moon rock science

“Each new sample gives us a big boost in understanding what’s going on, just because we still have so few,” Nemchin noted. “The Apollo samples have been worked on for the past 50 years and are still being actively studied.”

By analyzing the rocks reported by Chang’e 5, Nemchin and his fellow researchers first verified which types were present. In particular, they were after fragments of basalt, which correlate with volcanic activity.

“We had to get an idea of ​​the chemical composition of the fragments in order to be able to compare [them] to the large basalt field visible from orbit, ”he said.“ And, make sure [those] the fragments represent this basalt field and do not come from elsewhere. “

Then the scientists confirmed the specific age of the coins of interest. Validating that these fragments are young was one of the main objectives of the mission. This is how the team members expected to prove their hypothesis that the moon has active volcanoes more recently than the textbooks suggest.

“All the basalts we had before are over 3 billion years old,” Nemchin said. “We also had a few very young points determined from material ejected by very young impacts – impact melts – but nothing in between. Now we have a point right in the middle of the gap.”

Such age determinations are called crater counts, something the team hopes to continue to do in the future in order to reach the full range of rocks to map each generation of the moon. Nemchin also notes that some interesting chemical characteristics were found in the basalt samples, most notably a high iron content, which is not present in any other piece recovered from the lunar surface.

Further chemical research on the rocks, he says, will help answer new questions introduced by the team’s new findings, such as the search for The source of heat that led to lunar volcanic activity a few billion years ago.

And in the end, the Australian geologist stresses that “what is important for me in all of this is that we managed to bring in a large international group of people to work on the sample”.

“One way or another,” he added, “In the current situation where international travel is still rather restricted, I have had more interactions with different people than in previous years where we could move around however we wanted. “