Moon’s far side hides ancient asteroid that hit it 4 billion years ago

The Moon is a mysterious place, one battered by asteroid and meteor impacts over millions of years. These impacts have given it a bruised appearance, full of thousands of craters and an uneven surface.

But, there is more to it than meets the eyes and once such a discovery happened four years ago. A mysterious material lurking beneath the largest crater not just on the Moon, but solar system.

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Scientists detected a colossal mass of material beneath the Moon’s South Pole-Aitken basin, the largest crater in our solar system. This anomaly, which may consist of metal from an asteroid, was identified by researchers at Baylor University.

The study, led by Dr. Peter B. James, assistant professor of planetary geophysics at Baylor’s College of Arts & Sciences, suggested that the mass is so substantial it could be compared to a pile of metal five times the size of Hawaii.

The findings, published in the journal Geophysical Research Letters, indicated that this unexpected mass lies deep under the lunar surface, hundreds of miles beneath the basin.

LARGEST CRATER IN SOLAR SYSTEM

The South Pole-Aitken basin itself is an impressive geological feature, stretching over 2,000 kilometers wide — an expanse comparable to the distance from Kolkata to Mumbai — and plunging several kilometers deep. Its location on the far side of the Moon renders it invisible from Earth, adding to its mysterious nature.

To detect subtle gravitational changes around the Moon, the research team analysed data from Nasa’s Gravity Recovery and Interior Laboratory (GRAIL) mission, coupled with topographical data from the Lunar Reconnaissance Orbiter.

Their analysis revealed the presence of the mass anomaly, which is so dense that it is pulling the basin floor downward by more than half a mile.

One theory posited by the researchers is that the mass consists of metal from the asteroid responsible for creating the crater, which remains embedded in the Moon’s mantle. Simulations of large asteroid impacts support the idea that an iron-nickel core could be dispersed into the Moon’s upper mantle during a collision and remain there instead of sinking to the core.

Alternatively, the mass might be a concentration of dense oxides from the final stages of solidification of the lunar magma ocean.

The South Pole-Aitken basin, estimated to be about 4 billion years old, serves as a unique natural laboratory for studying the catastrophic impact events that have shaped rocky planets and moons across the solar system.

This discovery not only provides insights into the Moon’s geological history but also raises intriguing questions about the processes that have sculpted our celestial neighbours.