Parts of the Moon are older than we think

The “man in the moon” might be 200 million years older than we thought: that’s owing to a fresh analysis of the impact craters and samples recovered from the lunar surface by the Apollo missions. Richard Hollingham is a science journalist, author, and presenter of the Space Boffins podcast.

Richard - You have to think in geological time here, which I really struggle to get my head around. So the solar system formed around 4.6 billion years ago and the Moon formed very shortly after. And this period of the solar system formation was really chaotic. It was terrifying. If you imagine there's that scene in Star Wars, in fact, there's several scenes in Star Wars, where the Millennium Falcon bombs through an asteroid field. That's what the solar system was like, at least in the plane of all the material around the Sun. And so the Moon was formed by this Mars sized object hitting the Earth and pinging out to form the Moon and ending up in orbit. And we know that from the Apollo missions, we know that from these rocks, astronauts brought back 382 kilograms of rock from the Moon. So we know that, and this latest research really is just putting some refinement on the dates of sort of what happened afterwards, of when things hit the Moon, when events happened on the Moon. I guess painting a bit more of a picture of the early solar system.

Chris - Why does that matter? I don't mean that in a sniffy way, as in how does that inform, in terms of understanding the timing, what was going on when?

Richard - The Moon is almost like a perfectly preserved relic of the early solar system. On the other hand, we've had all sorts of tectonic movements. We've got the tectonic plates moving around volcanoes, earthquakes. It's really difficult to piece together what the early Earth was like. But we can see now what the early Moon was like. And just putting dates on this gives us a much better understanding of what the early solar system was like. We can use that to apply to other solar systems as we start to discover other solar systems, but also use it perhaps to figure out, well when did it all calm down and what sort of conditions would there need to be for life, whether that's on Earth or whether that's on Mars. So it's another little bit of the jigsaw of information on this.

Chris - So if we get a timeline on when things were and weren't hitting the planet because the Moon doesn't have tectonics, so it preserves the sort of timeline with all those crater impacts, we can tell when they were happening on the Moon and getting the dates right kind of matters. We know the Earth was probably subject to the same sort of thing. Then it tells us a bit more about the conditions at that point in Earth's history, which is pretty important for when we think life was beginning to get started.

Richard - Absolutely, yeah. Gives us a really good sense of what the early solar system was like and we've just learned so much from these missions to the Moon and still I find it remarkable. We're still learning from the Apollo missions. I mean the last one of those was in 1972. I mean, it is just amazing.

Chris - It is amazing. I'm quite glad we've got you here because I was going to ask you, because India is about to launch another mission to the moon and this will be the fourth country to land on the moon and they're heading where NASA wants to head, aren't they? Down to the south pole of the moon. What can you tell us about that?

Richard - Yeah, so they launched last week. It's on its way to the Moon, due to touchdown in August. So yeah, as you say, the fourth country to land on the Moon. But this is going to the lunar South Pole. If it works, if it lands softly, they've got a rover. This will be the first mission soft landing and exploring the lunar South Pole. That matters because an earlier Indian mission found evidence of water ice in that area and astronauts are heading to the lunar South Pole. So the next astronauts to walk on the Moon will probably be going there. If there's water there, well, that's great news because that means they can, in future, if we have a lunar base or whatever, use that water to live on.