This is Scientific American's 60 Second Science.

I'm Christopher Intagiyata.

On July 20, 1969, humankind finally set foot on the surface of the moon.

50 years later, a big mystery remains.

How the heck the moon got there in the first place.

For decades, the thinking on that has been that four and a half billion years ago,

a Mars-sized protoplanets

smashed into the Earth. When the dust settled, our moon remained, forged from the

debris of Earth and that other object. The problem is as scientists have taken more and more precise isotopic

measurements of the moon, they've found that it's nearly identical in composition to the

earth, not some other object.

A problem that I've been advertising is an isotopic crisis.

Jay Milosh studies planetary impacts at Purdue University. Now he says a new theory

in the journal Nature Geo Science may at least point to a way out of that isotopic crisis

of the Moon's chemical isotopes so closely resembling Earth's.

Here's the idea. The authors, a team of Japanese scientists, write that maybe in those with oceans of the solar system.

The Earth was sloshing with oceans of magma.

Then, when the Mars-sized objects slammed into those molten seas,

their models predict a lot more Earth-derived

material gets ejected into orbit in the form of scorching vapors.

Temperatures of tens of thousands of degrees and so that expands at speeds that exceed the escape

velocity of the Earth and in that way it injects material into orbit around the

...