The professor asked us to think about the topic
The professor asked us to contemplate the topic. 70s we got a bunch of samples from the moon but it’s been almost 50 years since then and we haven’t been back since so scientists are stuck with what they’ve got and that’s why some of the moon’s geological activity remains a mystery
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So you may have heard lots of hullabaloo lately about humans going back to the Moon, and there are a bunch of reasons to head up there again, from scratching humanity’s itch to explore the unknown, to more practical things like mining. But from the surface of our dynamic and ever-changing planet, it might seem like those journeys will be a little bit boring. It’s easy to dismiss the Moon as a lifeless, frozen rock, because we can’t currently go inside the Moon to check on how geologically active it is. We have to rely on clues from its surface to tell us what’s going on, and some of those clues tell us that the Moon could very much be alive.
Before we talk about the Moon’s reputation for being geologically dead, we need to talk about how it was born. We think the Moon formed about four and a half billion years ago, back when the young Earth hadn’t quite grown to its full size. Our proto-Earth and a Mars-sized planet called Thea had a bit of an altercation; they smashed right into one another and most of their guts ended up merging together. But this galactic car crash also threw tons of material into space, which eventually coalesced to form our Moon.
The baby Moon would have loomed large in Earth’s sky; their mutual gravitational tugging may have caused massive tides of lava to spill over the surface. The Moon would have glowed red hot from the surface down into the core, and it’s been slowly cooling down ever since. But cooling isn’t the same as frozen, and if there are still some liquidy bits churning around beneath the surface, we might see signs on the surface as recently solidified lava.
When we look at the Moon, we see a bunch of gray splotches called Maria, which is Latin for seas. They’re darker in color from the rest of the surface because they’re made of a different kind of rock called basalt; that’s a type of frozen lava, so planetary scientists are pretty sure Maria are evidence that the Moon was once geologically active. But is it still, and if not, how long ago did that end?
Well, it turns out dating the Moon can be tricky, and scientists have two main strategies. The first is simply looking at craters; if a smaller crater is on top of another, we know that that crater has to be younger, otherwise it would have been destroyed when the larger meteorite hit. We can also look at the number of craters in an area; generally, the greater the crater count, the older a patch of rock is, because space rocks have had more time to smash themselves into it. These are both forms of relative dating; craters can’t tell us the absolute age of a particular part of the Moon, but we can use them to tell how old a feature is compared to another one, and most of the Moon’s surface appears to be billions of years old.
But by counting craters, scientists have identified lava that may be a mere 18 million years old. If the Moon were my age, that’s like less than two months ago. But to confirm it’s actually that young, we need to get our hands on actual rock samples to get a precise age, and that’s where the second dating method comes in. We can cross-reference crater counts with radiometric dating to get a baseline for age estimates. Radiometric dating looks at the composition of the rocks themselves; some isotopes, or versions of atoms, are radioactive and break down over time, and they do that breaking down at a very predictable rate. So to estimate how old a given Moon rock is, scientists will compare two measurements; how much of the original isotope is left versus how much there is of the stuff it decayed into.
Unfortunately, real lunar samples are a little bit hard to come by; you can’t exactly just pop up there whenever you like to date whatever part of the Moon you want. With the Apollo missions of the 1960s and 70s, we got a bunch of samples from the Moon, but it’s been almost 50 years since then, and we haven’t been back since. So scientists are stuck with what they’ve got, and that’s why some of the Moon’s geological activity remains