A Lunar Rock’s Astonishing Secrets

In a surprising turn of events, a simple rock collected from the moon’s surface over 50 years ago could change what we know about the early days of the moon and the entire solar system. This rock, gathered during the Apollo 17 mission, may hold astonishing secrets about the moon’s origins and the history of cosmic impacts.

Rock 76535 and Its History

The rock, cataloged as 76535, features a chemical composition and texture indicating it formed deep within the moon’s crust, about 50 kilometers below the surface. Radiometric dating suggests this rock has been on the moon’s surface for 4.25 billion years.

The prevailing assumption was that this rock was ejected from the moon’s depths due to a massive impact, with some believing the South Pole-Aitken Basin, the largest impact site on the moon, was responsible, especially given their similar ages.

New Simulations and Different Interpretations

However, new simulations suggest that rock 76535 may have formed underground where it was found at the Apollo 17 landing site in the Taurus-Littrow Valley on the eastern edge of the Sea of Serenity.

There have long been doubts about the South Pole-Aitken Basin being the source of rock 76535, particularly since the rock shows no signs of having been subjected to violent events. Detailed computer simulations conducted by Evan Bions from the Lawrence Livermore National Laboratory in California offer a simpler local explanation for how the rock appeared in the Sea of Serenity.

How Did the Rock Reach the Surface?

The simulations showed that large impacts could raise deep rocks to the surface without subjecting them to excessive shock. During the final stages of the impact that formed the Sea of Serenity, the floor of the new crater could collapse, allowing materials to flow more freely. In the simulation, as the floor collapsed, up to 140,000 cubic kilometers of material could be gently pushed to the surface.

This explains the lack of signs on rock 76535 indicating it was exposed to shock or excessive heat, as it simply rose to the surface through the liquefied crust following the impact that formed the Sea of Serenity.

Implications for Our Understanding of Cosmic History

If rock 76535 was ejected 4.25 billion years ago, this means the Sea of Serenity must have formed at the same time, which predates previous scientific estimates by 300 million years. If the Sea of Serenity basin is older, other lunar impact basins might also be older.

Since the moon’s airless surface is often used to calibrate impact rates in the early solar system, any change in the timeline of events on the moon will affect the timeline throughout the rest of the solar system.

Conclusion

With astronauts set to return to the moon, there is a perfect opportunity to confirm these findings, as the same processes may have occurred in other lunar seas. Future missions might find rocks similar to rock 76535 on the surface that can be brought back to Earth for further investigation. These discoveries not only expand our understanding of the moon’s history but also reshape our perception of historical events in the solar system.