New research reveals that as much as one half of all of Earth’s current water supply is older than the Sun.
An international team of scientists led by Ilse Cleeves at the University of Michigan looked back into creation of Earth and our solar system to find out where all of the water came from.
Some scientists think Earth’s supply of life-sustaining H2O was the result of chemical reactions that took place as the Sun and solar system began forming some 4.6 billion years ago.
Others theorize that today’s water originated about a million years earlier in the cold recesses of interstellar space from a molecular cloud that later provided material to form the sun and planets.
To reach their findings, Cleeves and her colleagues simulated the chemistry of our solar system as it was forming and then compared the ratio of two slightly different types of water, one that was plain H2O and the other, ‘heavier type’, that had been enriched with deuterium – an isotope of the hydrogen molecule.
The researchers found that the water in Earth’s oceans as ice found in comets have a higher ratio of the ‘heavy water’ to the deuterium free water than the Sun contains.
“That’s obviously a clue for what’s going on and it suggests that that very cold chemistry is required to produce these very large enrichments in the heavy isotopes deuterium in the water,” said Dr. Conel Alexander from the Carnegie Institution for Science, who was a member of the research team.
Alexander said that this very cold chemistry, about 10 to 30 degrees Kelvin – -263.15 to -243.15 Celsius – had to have ionizing radiation around in order to overcome the activation barriers that stop typical chemistry that takes place at the extremely cold temperatures.
The scientists considered two possible locations that may have allowed the cold chemistry.
One would be in the ancient molecular clouds (also called stellar nurseries) where stars form.
The other location would be in very cold regions of protoplanetary disks, which form solar system bodies such as planets, moons, asteroids, and others that surround developing stars.
But Cleeves realized that young stars that are surrounded by these planet-forming disks produce some very intense solar winds.
These solar winds, according to Alexander, would prevent galactic cosmic rays – one of the major sources of ionizing radiation – from even entering those disks, something that may very well stop deuterium-enriched water from forming.
This realization helped Cleeves create a complex model for the chemistry that existed within the planetary disks.
Alexander said the model did indeed show that deuterium-enriched water cannot be made in the disks, which led the group to conclude that it was produced within molecular clouds found in the interstellar medium.
“Ultimately, the intriguing idea is that you’re bringing in ices from the interstellar medium, pretty much intact, and those ices have a lot of organic material in them and some people have speculated that the organic material in meteorites and comets may have helped kick-start life,” said Alexander.
“If that’s true, and our solar system is fairly typical, then fairly similar superable organic material and water/ice is coming into most forming solar systems.”
This could, Alexander said, make the potential for life in other solar systems significantly more probable.
You can listen to the Science World radio interview with Dr. Conel Alexander either through the player below or check out the entire show at the times and places listed in the right side column.