Earth’s oceans may have formed directly from the ‘stellar matter’ that accumulated in the early solar system, according to new research – challenging the idea that most of Earth’s water here was supplied by meteorites and comets.
Scientists who studied rare meteorites thought to have formed in the hot inner solar system found that ancient rocks contained more hydrogen than previously thought – and hydrogen, along with oxygen, is one of the two essential ingredients of water.
If the earth were made of similar materials, then more than enough hydrogen would have been available to combine with oxygen to make all the water in the world – in fact many times more.
“The Earth could have been wet from the beginning when it began to form,” said Laurette Piani, a cosmochemist at the Petrographic and Geochemical Research Center in France and author of a paper on the new findings published Thursday in the journal Science. .
Early models of the formation of the solar system suggested that the earth had to be very dry because it formed so close to the hot young sun. Instead, it flows with life-sustaining water.
Scientists have been trying for years to explain the mystery and develop a theory that the young earth was bombarded by water-rich meteorites and icy comets from the frozen outer solar system, which became our oceans, lakes, rivers and clouds.
But this exotic proposal does not correspond to vertical chemical traces in the Earth’s composition, nor does it directly explain the many oceans of water that are trapped underground in the Earth’s rocks.
Piani and her colleagues studied enstatite chondrite meteorites that were thought to have formed in the hot inner parts of the solar system more than 4.5 billion years ago, in addition to Earth and the other rocky planets.
Only about 200 enstatite chondrite meteorites have been found, but they correspond to specific aspects of the chemical composition of our planet.
This suggests that they are similar to the “building blocks” that the Earth formed from an interstellar nebula – “star dust” – in the early solar system, Piani said.
The researchers used special procedures to analyze the meteorites, including their monsters gently heating for several days to remove groundwater that they contaminated after falling from space.
They found more hydrogen in their minerals than expected – enough that the hydrogen in similar materials could have combined with oxygen to make at least three times all the water known to exist on Earth, both on its surface and deep underground.
“Our discovery shows that the earth’s building blocks may have contributed to the earth’s water,” Piani said. “Hydrogen-bearing material was present in the inner solar system at the time of the rocky planet formation, although the temperatures were too high for water to condense.”
The study also suggests that the subsequent bombardment of the outer solar system may still have occurred, but it would have made only a small contribution to our surface water, and no significant contribution to the water in the earth’s rocks.
“The interior water can be explained by internal solar system material,” Piani said. “We calculate that only 5 percent of the surface water was inherited from material from the outer solar system.”
The study “brings a crucial and elegant element to this puzzle,” wrote planetary scientist Anne Peslier of NASA’s Johnson Space Center in Houston, in a scientific article published in Science. “Earth’s water may have just come from the nebulous material from which the planet is drifting.”
Rick Carlson, a geochemist and director of the Earth and Planets Laboratory at the Carnegie Institution for Science in Washington, DC, said the study reinforced the idea that the Earth formed from a mixture of materials from the early solar system.
It also showed that the earth was relatively “dry” compared to other bodies in the solar system, despite its visible abundance of water; it still contained enough hydrogen when it formed, to make up the oceans of water we now see, and more.
‘Even a dry meteorite like an enstatite chondrite has enough water in it [account for] all the water of the earth, ‘he said. “I think that’s a pretty fun discovery.”
