4.5 billion years ago, a planet the size of Mars whizzed through the solar system. In the way stood our pure young globe.
The collision was astronomical. Literally.
Again, our future home stood hazy, surrounded by a cloud of smashed rock and dust. Over time, the cloud slowly clumped together into a huge sphere.
The moon was born.
But even though our nearest neighbor is important to us, there is still much we do not know about the creation of the moon.
Now, scientists at NASA have discovered that far more metal is hiding under the moon’s surface than previously thought. This can give us new insight into how the moon ended up in the sky.
Scouted for ice cream
First, a bunch of acronyms:
The NASA scientists who made the discovery are responsible for the MINI-RF instrument mounted on the LRO vessel.
LRO stands for Lunar Reconnaissance Orbiter, which is one of NASA’s most important satellites around the moon. It is tasked with mapping the moon’s surface for future missions.
MINI-RF is an abbreviation for Miniature Radio Frequency, which is a radar tool on board the satellite. This radar is used, among other things, to scout for ice in the shady slopes of the lunar craters.
It was this radar that during the ice hunt suddenly gave unexpected findings.
Where does the moon actually come from?
The Earth is 4.55 billion years old. The moon must have begun in its orbit 60 million years after our planet formed.
When so many millions of years have passed, it is not easy for scientists to reconstruct the course of events.
Among the now disregarded theories about the origin of the moon, we find the theory that a fast-spinning globe must have thrown the lunar material out of its own body, through forces such as in a centrifuge.
Another theory has been that the earth caught a neat finished moon in orbit around it.
Although the theory of one giant collision is now the leading theory, some researchers believe that there may have been a series of collisions. 20 minor collisions would be enough to create the moon, believes the research group behind this theory.
The chemistry is missing
The theory that the moon is a collection of dust from a solid collision between our newborn planet and another planet has a natural consequence.
If much of the material came from Earth, the moon’s chemical composition should resemble our planet. But a look at the moon’s surface creates headaches.
An astronaut strolling on the moon’s highlands – the light gray plains that encircle the craters – will find rocks that have significantly less metal-bearing minerals than on Earth.
This can be explained by the fact that the soil before the collision had sorted into three layers – core, mantle and crust. In that case, many of the earth’s metallic substances would have sunk deep into the core, before the alien planet could tear them apart.
But if the same astronaut went for a walk in the lunar oceans, the dark fields created by lava from the lunar interior, he would encounter more metal-rich stones than are common on earth.
This disparity has made researchers scratch their heads. How much of the moon actually comes from the planet orbiting our planet?
Metal with dust
This is where the MINI-RF team comes into the picture.
The scientists used the radar to analyze the dust on the moon. They were particularly concerned about the craters, which are created by meteors that have collided with the moon.
They found that the dust at the bottom of the craters had more metal in them than on the surface. And the larger and deeper the crater was, the more metal there was in the dust.
This finding kicked open the doors to a new opportunity:
The largest craters have been excavated by large meteors that may have torn up iron and titanium from deep below the surface.
If the hypothesis is correct, it means that only the top layer of the moon is poor in metals. If we peel off a couple of hundred meters, we may encounter a proper metal mine.
This may also explain why the highlands are so metal-poor, while the low-lying areas have more metal.
To check the findings, the researchers compared their own radar images with other maps of lunar metals from NASA and from Japan.
Everything was fine.
Signs of close relationship
– This exciting discovery shows that even after the satellite has been around for eleven years, we are still making new discoveries about our nearest neighbor’s history, says NASA scientist Noah Petro in a press release.
The research team emphasizes that the study does not directly provide answers to how the moon came to be, but they believe it provides important information that can be assessed against previous hypotheses.
Scientists have now thrown themselves over the craters in the moon’s southern hemisphere to see if the same trend can be found there.
Reference:
Heggy, E. m.fl: Bulk composition of regolith fines on lunar crater floors: Initial investigation by LRO/Mini-R. Earth and Planetary Science Letters, 2020. Summary.
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