Scientists found new evidence that show that water was on Earth since the beginning of the planet’s development, discarding the theory that water appeared thanks to an asteroid collision.
Researchers believe that H2O dust grains that accumulated millions of years ago to form the Earth retained liquid water when the planet was born. According to this theory, this dust was part of a disk around the Sun, later gathering to develop the planet.
The comet explanation has been the most accepted, due to the fact that icy comets are the largest water-rich celestial bodies in the solar system. Nevertheless, Dr. Hallis, lead author of the study, said that water covering the Earth doesn’t have the same hydrogen composition as comets.
In order to provide evidence of these assumptions, scientists had to find samples of the early stages of Earth, as the water surface now isn’t likely to represent the original water surface on the planet.
Scientists had to collect evidence from deep down Earth, looking for a reservoir of water that remained unaffected since the planet’s formation. In the end, scientists thought about analyzing volcanic rocks as they consider it “time-capsule clues.”
The rocks selected were formed from lava spelled-out during volcanic activity in Iceland and on Baffin Island, in northern Canada. These rocks were originated with material that came deep below the surface, probably there since Earth’s formation.
“What we’re actually measuring is small pockets of trapped glass inside mineral grains,” explains Dr. Hallis. This glass is lava trapped inside the rock, meaning that it has been protected from contamination by surface water, perfectly preserved. Using an ion microprobe, scientists detected water molecules and its composition.
Chemical evidence
Karen Meech, co-author of the research, explains that this composition works as a “chemical fingerprint.” She explained that they have to compare this water fingerprint with elements on space, and other materials on Earth, in an interview to the Christian Science Monitor. The hydrogen composition found on these rocks differ of those in comets, evidence that discard that previous theory.
Nevertheless, some scientists believe that the Earth was too hot at the beginning to have water in the first place. The heat involving the forming process could have boiled all the water molecules away.
However, Dr. Hallis said that even though a big amount of water could have been lost due to evaporation, she believes that enough water survived to form our oceans, seas, rivers, etc.
Looking for water outside
Researchers believe that these type of studies can help us in the hunt for other planets that may contain water.
“We’ve got over 6,000 exoplanet systems or candidates that are known now and many of those have worlds in their host star’s habitable zone,” Dr. Meech says.
If their theory about the dust particles and water formation gets confirmed, that could be huge news, as the probability of finding water-rich planets elsewhere is very high, researchers believe.
Source: Journal Science