The Earth's oceans may have originated from comets, a once-outlandish notion that got further support Wednesday when astronomers reported on ocean-like water in one comet.
An international team of researchers found that the water coming from the comet closely matched the chemical composition of the current oceans, an observation suggestive that a significant portion of the Earth's oceans may have come from comets eight million years after the planet itself formed.
Life would not exist on Earth without liquid water, and so the questions of how and when the oceans got here is a fundamental one, said Ted Bergin, astronomer at the University of Michigan, part of the team that made the discovery. It's a big puzzle and these new findings are an important piece.
The findings were published online Wednesday in Nature.
Astronomers have known for a decade that comets can contain water after the comet LINEAR broke apart as it passed the Sun, an observation made in 2000 and published the next year in Science.
The idea that comets seeded life on Earth with water and essential molecular building blocks is hotly debated, and for the first time, we have seen a comet with the right composition to do the job, study lead author Michael Mumma, of NASA's Goddard Space Flight Center, told NASA Science News in 2001.
The new observation with Hartley 2, the first comet to have ocean-like water, expands the notion that comet water may already have had the chemical mix found in oceans.
This result substantially expands the reservoir of Earth ocean-like water to include some comets, and is consistent with the emerging picture of a complex dynamical evolution of early solar system, the authors conclude in their study.
Comets may have also delivered water to the Moon, researchers noted in January.
Astrophysicists led by James Greenwood of Wesleyan University in Connecticut analyzed lunar rock samples and found that water-loving minerals on the moon had atomic signatures similar to comets. The research was published in January in Nature Geoscience.
Lawrence Taylor, planetary researcher at the University of Tennessee, Knoxville and contibutor to the Nature Geoscience study, along with colleague Yang Liu, wrote that the current study might suggest that the solar system may contain more water with ocean-like qualities than expected.
This claim, if substantiated with additional measurements in future, suggests significant modifications on current models of early solar system dynamics and origin of water in inner solar system bodies, the researchers, who were not involved in the current study, wrote in an email to IB Times.
It is imagined that during the early formation of the Earth-Moon system, just after the Giant Impact, the Earth already had most of its water, but the Moon has none, the researchers wrote.
In the current research, Geoffrey Blake, planetary scientist at the California Institute of Technology, lead a team of researchers who used the Herschel Space Observatory to measure the deuterium, a heavy form of hydrogen, in Hartley 2's water.
The source of Earth's oceans has been debated among astronomers for decades. Most thought asteroids supplied most of the Earth's water, but that view may change.
The results show that the amount of material out there that could have contributed to Earth's oceans is perhaps larger than we thought, said Bergin.