Formation of Moon a 'hit and run' accident?

According to scientists, it is certain that some sort of impact from another body freed material from the young Earth and the resulting debris coalesced into today's Moon.

But the exact details of the impactor's size and speed have remained debatable, the 'BBC News' reported.

In recent years, scientists' best guess for how the Moon formed has been that a relatively slowly moving, Mars-sized body called Theia crashed into the very proto Earth.

The event would have heated both of them up and released a vast cloud of molten material, much of which cooled and clumped together to give rise to the Moon.

It suggests that the Moon is made up of material from both the early Earth and from Theia, which should be somewhat different from one another.

What has complicated matters is a number of observations of "isotopic compositions", the ratios of naturally-occurring variants of some atoms taken from the Earth and from lunar samples.

While the Moon has an iron core like Earth, it does not have the same fraction of iron and computer models supporting the Theia impact idea show just the same thing.

However, the ratio of the Earth's and the Moon's oxygen isotopes is nearly identical, and not all scientists agree on how that may have come about.

Confounding the issue further, scientists reporting in Nature Geoscience have proposed that the Moon was somehow cleaved from the Earth itself.

Andreas Reufer from the Center for Space and Habitability in Bern, Switzerland, and colleagues have run computer simulations that suggest another possibility: that a far larger and faster-moving body made an even more glancing blow with the young Earth.

They said this body would have lost only a small amount of material and most of it would have continued on after the "hit-and-run".

That results in a much hotter disc of debris from the collision, but matches up with what would be needed to make a Moon-sized body.