"Up to half of the water on Earth is likely older than the solar system itself, University of Michigan astronomers theorize."
The age of the water is counted from the time that oxygen and hydrogen atoms combined to form a water molecule. You might naively think that this combination occurred after formation of our solar system. But Ilse Cleeves (doctoral student in astronomy) and Ted Bergin (professor of astronomy) estimate that between 30 and 50% of the water formed a million years before the solar system formed, when there was only a molecular cloud of gas, but no sun or planets.
This estimate was obtained by looking at the ratio of hydrogen isotopes within water. The hydrogen atoms in water come in three forms, hydrogen-1, hydrogen-2 (known as deuterium) and hydrogen-3 (known as tritium). Tritium is radioactive and decays into helium-3; it is virtually non-existent in the solar system except on the surface of the earth. But hydrogen-1 and hydrogen-2 are common. Comparing the ratio of hydrogen-1 and hydrogen-2 within samples of water, hydrogen gas or other compounds tells scientists about how these materials were formed. For example we find the ratio within comets and water in the Earth's ocean is higher than the ratio found in hydrogen atoms in the sun.
For more details see....
- ▼ November (5)
- ► 2013 (24)