Terrawatch: Rare gas points to deep nebula origins for Earth

A vital clue to our planet's origins is a rare isotope of helium bubbling up along mid-ocean ridges.

Each year, the Earth leaks out of the 2 kilogram of Hem 3 that is enough to fill a balloon the size of your desk. It is rare on the Earth's surface today and most of it is from the big bang, where it would have been incorporated into planets as they grew out of the dust and debris.

The University of New Mexico's Peter Olsen and Zachary Sharp used the modern leak rate to estimate how much of it is still in the Earth's core. Their results show that the core still has a huge amount of helium-3 up to a petagram.

The most likely way for our planet to acquire such high quantities of gas within its interior is for it to have formed deep within an active solar nebula.

The evidence will be strengthened by finding other nebula-created gases, such as hydrogen, leaking at similar rates and from similar locations.