A new space mission could put some old debates to rest

Dec 6, 2013 16:22 GMT  ·  By
Studying the isotopic composition of Venus may reveal more data on how the Moon formed
   Studying the isotopic composition of Venus may reveal more data on how the Moon formed

Determining the isotopic composition of Venus might provide researchers with the data they need to finally establish whether or not an impact with a Mars-sized object early on in Earth's history led to the formation of the Moon. This theory has been circulating for decades, but new evidences cast some doubts on its validity. 

Currently, planetary scientists believe the Moon appeared about 4.5 billion years ago, shortly after our planet first solidified from the young Sun's debris disk. Around the same time, another planet in the solar system, estimated to have been around the size of Mars, struck our planet.

The impact is believed to have been so devastating that the two objects merged, while a huge chunk of both was ejected into space and captured by Earth's gravity as the Moon. However, not all scientists are convinced that this explanation can stand to rigorous scrutiny.

The main issue with this theory is that the isotopic composition of material harvested from the lunar crust appears to be nearly identical to that of similar rocks from our planet. If the giant-impact theory were true, scientists explain, then the lunar crust should have largely contained the isotopic signatures of the Mars-sized body that struck Earth long ago.

Despite having formed around the same time, it is highly unlikely that both our planet and the impactor that struck it had the same isotopic composition. “The oxygen isotope composition of Mars, for example, differs from that of the Earth by more than a factor of 50,” says expert Robin Canup.

“If the impactor was as different from Earth as Mars is, its signature would still be detectable in the moon, even after a giant collision,” the scientist writes in the December 4 issue of the journal Nature. Canup is based at the Southwest Research Institute, in Boulder, Colorado.

This is precisely why a new mission to analyze the surface of Venus would make so much sense. As the closest planet to Earth – with the exception of Mars, which is already being investigated thoroughly – its surface could hold more data about what really happened 4.5 billion years ago.

“We do not know the isotopic composition of Venus, the planet most similar to Earth in both mass and distance from the Sun,” Canup says, quoted by Space.

“If Venus' composition proves similar to that of Earth and the moon, Mars would then seem to be an outlier, and an impactor composition akin to Earth's would be more probable, removing many objections to the canonical impact,” he concludes.