After decades counting craters on the Moon, a 30-year mystery, a Chinese probe and a volcanic stone want to revolutionize the way we date things in space
“Can not be”. I imagine that after seeing that, still incredulous, he disassembled the telescope and cleaned the lenses one by one; He put them back inside the tube that, according to some, he had reused from a damaged organ and, after rubbing his eyes, he found that yes, it was not a mirage, nor a visual illusion. It wasn’t even the whimsical effect of an aberration produced by the imperfection of crystals. No, no, it was clear: there were seas on the Moon (or, at least, something very similar). We are in 1610 and a 45-year-old Galileo is about to do something that will continue to this day in the form of cartographic maps.
‘Maria’ (‘seas’ in Latin) would write the Pisan genius joining a tradition that comes from’ The metamorphoses of and would leave us a rosary of oceans, lakes, marshes and bays spread over the surface of the Moon. The problem, of course, is that they are not seas. Are huge basalt plains formed by ancient volcanic eruptions. And it is that, although it may seem strange to see it there, pale and dying, there was a time when our satellite was a hell of sulfur and basalt. The funny thing is that this “time” was less than we might think.
A mystery of more than 30 years
In the year 1971, Apollo 15 crews photographed something very strange on the surface of the Moon. Nobody was very clear what it could be. Above all, because, although they seemed to be the remains of a volcanic eruption, logic told us it could not be. By the 1970s we already knew that there was nothing strange about talking about lunar volcanoes, but the lunar seas were very old basaltic flows with billions of years. The problem is that ‘Ina’, as the rare discovery was called, was not a billion years old.
How can we tell how old things are on the Moon? Incredibly, the traditional method of determining the age of lunar structures is to count craters. That is, counting the number of meteorite impacts that a surface has. The Moon, like the Earth, receives a permanent “drizzle” of meteoroids that impact its surface and leave scars on its topography. What happens is that, unlike our planet, there are no erosion processes that make them disappear. Therefore, the older a landscape is, the more craters it contains.
So, fearing the worst, NASA scientists turned to the Lunar Orbiter 4. In 1967, the North American probe had orbited the satellite taking more than 400 ultra-high resolution photos that covered 99% of the visible side of the Moon. in resolutions ranging from 58 to 134 meters. If ‘Ina’ was something real, it must be in those photographs.
But it was not. And not because the discovery zone appeared with a different aspect. It was not there because due to a technical failure, the exact place where ‘Ina’ was located was part of that 1% of the visible face that had not been photographed. That meant that, for more than 30 years, the strange discovery of Apollo 15 remained a mystery that no one could explain.
‘Ina’ was never alone
In 2014, a team of researchers led by Sarah Braden, a professor at Arizona State University, decided to give the mystery a twist. Using the Lunar Reconnaissance Orbiter, a probe that has been mapping the satellite’s surface since 2009 with a resolution never seen before, the team discovered 70 places very similar to the original ‘Ina’.
I used to say that ‘Ina’ was not a billion years old, but many of those 70 places seemed to be less than 100 million years old. Something that may seem like a long time, but in geological terms it is a breeze. At the time, in 2014, the discovery by Branden and his team excited planetary scientists. That It could mean that the Moon was “more alive” than it seemedNot only could its core be warmer than we expected, but (who knows?) there was a possibility that we would see a lunar eruption at some point.
The age of things in space
Now, China’s Chang’e-5 lunar probe has just taken “a small step” to confirm that recent volcanism. As we told you months ago, thanks to Chang’e-5, China became the third country to bring lunar samples to Earth. But the most interesting thing about the expedition is that, thanks to her, We were going to be able to calibrate the crater counting system that until now we used to know the age of lunar surfaces.
The Chinese team has used lead isotope dating to conclude that those rocks formed from magma that erupted about 2 billion years ago. This data is more intriguing than it seems because would mean that those rocks formed much later than in other known volcanic lunar samples and we don’t have many explanations for it.
However, that is not the most interesting in the medium term. The most interesting thing is that, by calibrating the crater counting system with greater accuracy, we will be able to better understand the geological history of innumerable celestial bodies and we will give a much more accurate measurement of the age of space.
Image | Neven krcmarek