Moon Maker: Scientists Sift Apollo Rocks To Figure Formation

The moon may be a mainstay of the night sky, but scientists believe they're one step closer to understanding where it came from with the help of new research into rock samples brought back by Apollo astronauts. Existing theories that a huge impact of an unknown planet with Earth billions of years ago spawned the debris that would later cluster to create the moon was believable, but discrepancies in the science had always left scientists scratching their heads.

The problem was oxygen, and other chemicals in the composition of the moon, the Earth, and other planetary bodies. Slight differences in the isotopes of those chemicals present – perhaps the balance of Oxygen-16 (O-16) to Oxygen-17 (O-17) – act as a "fingerprint" of the origin of asteroids and other rocks, allowing astronomers to figure out where they came from.

Unfortunately, the moon's fingerprints didn't quite match up to expectations. Going by the original theory, its composition should be markedly different from that of Earth, because scientists predicted it to be mostly foreign body and with a little external rock from our own planet.

Instead of the 70- to 90-percent of foreign material, however, samples from the early Apollo moon missions have shown little in the way of differences from Earth rocks' chemical fingerprints.

Thankfully for the frustrated scientists, new results from a team led by Daniel Herwartz of the University of Cologne in Germany have cast fresh light on the samples.

Using an upgraded mass spectrometer – "an order of magnitude better" than what other labs have access to, team member Andreas Pack boasts – and samples from Apollo missions 11, 12, and 16, the study found that in fact there really is a difference between Earth and the moon.

That amounts to 12 parts-per-million in the OS-17 to OS-16 ratio, and had been hidden from less accurate scans in the past by the fact that the composition of Earth to foreign object mass is now believed to be 50:50.

Of course, questions still remain, like whether there are other potential causes for that ratio difference. A subsequent asteroid strike introducing more foreign material to Earth's crust could be one explanation, it's suggested.

SOURCE Science