“Imagine a pile of metal five times the size of the island of Hawaii (which is 10,432 km² in size) and bury it. That is what we have detected ”. This is said on the phys.org website by Peter B. James, lead author of the research at Baylor University (Texas) who has found a mysterious mass of material under the Aitken basin of the south pole of the Moon, one of the largest craters Of the solar system.
James and his colleagues suspect that the buried material contains metal from the asteroid that collided with our satellite some 4,000 million years ago created this crater, oval in shape and 2,000 kilometers wide, equivalent to the distance between Madrid and Copenhagen. Despite its size – it has a mass of at least 2.18 × 1018 kg – the discovered anomaly is not visible from Earth because it is on the far side of the Moon.
Fit the puzzle
The study, published in the journal Geophysical Research Letters, has been based on the analysis of data collected by two NASA missions: those of the Inner Laboratory and Gravity Recovery, which mapped the gravitational field of the Moon to determine its structure. inside. And the topographies obtained by the Lunar Reconnaissance Orbiter probe, launched in 2009 and which continues to send very valuable information from our satellite.
By combining that data, the scientists, looking for subtle variations in lunar gravity, discovered that there was a large mass of material buried down to a depth of about 300 kilometers below the Aitken Basin. One of the explanations for its origin is that it is metal from the asteroid that formed this crater and that continues to be embedded in the lunar mantle.
Computer simulations of large asteroid impacts indicate that under the right conditions, the iron-nickel core from which it fell on the Moon could have been dispersed in the collision across the upper part of the mantle, the layer between the crust and the nucleus, which on the far side of the Moon begins 150 kilometers from the surface.
Another explanation for the presence of the metallic mass is that it could be a concentration of dense oxides, associated with the last stage of the solidification of the magma ocean that covered the lunar surface 4,400 million years ago.
This hypothesis is based on the most accepted theory about the origin of the Moon, which would be the product of the impact with the Earth of an object the size of Mars, which occurred about 4,500 million years ago. The debris from the collision would have formed our satellite, which spent 100 million years covered in a molten lava-like layer. This crystallized in a process that would have pushed up the lighter rocks, which formed the lunar crust.
A natural laboratory
The Atkin Basin is extraordinary because it is the largest preserved impact crater in the Solar System. It is thought that there have been collisions of greater magnitude in our little galactic neighborhood, but of most there is no trace.
According to James, this enclave of the lunar south pole is “one of the best natural laboratories for the study of catastrophic space impacts, a set of very ancient phenomena that formed all the rocky planets and moons that we see today in our system.”
Image (NASA / Goddard Space Flight Center / University of Arizona): This colored graph shows the topography of the far side of the Moon. Warmer tones indicate elevation, blue tones the opposite. The Aitken Basin appears in a stronger blue. The dashed circle indicates the location of the anomalous mass that we have described.
