Earth may have formed much faster than previously thought after being born as tiny millimeter-sized pebbles that accumulated over only a few million years.
The new theory also suggests that rather than water being delivered to Earth by icy comets, this vital ingredient for life is present on our planet as our young planet absorbs water from its space environment. This theory could have important implications for the search for life outside the solar system, suggesting that watery and habitable planets around other stars may be more common than currently expected.
The new theory put forward by the team proposes that about 4.5 billion years ago when the Sun was a baby star surrounded by a disk of gas and dust, known as a protoplanetary disk, tiny dust particles would be quickly sucked up by formation. Planets once they reach a certain size. In the case of the infant Earth, this “discharge” of disk material ensures the supply of water to our planet.
“The disk also contains many icy particles. Since the vacuum cleaner effect draws in the dust, it also picks up part of the ice,” team member and Ph.D. said Isaac Onyet, a student at the Center for Star and Planet Formation at the University of Copenhagen. “This process contributes to the presence of water during Earth’s formation, rather than relying on a chance event to deliver water 100 million years later.”
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“People have debated how planets form for a long time,” said University of Copenhagen geochemist and member of the team behind the theory, Martin Schiller, he said in a statement. “One theory is that the planets formed from the gradual collision of bodies, gradually increasing their size over 100 million years. In this scenario, the presence of water on Earth would need some kind of serendipitous event.”
One example of such a coincidence is the bombardment of the planet by icy falling comets during the final stages of its formation.
“If this is how the Earth was formed, then we are lucky that we have water on Earth,” Schiller said. “This makes the chances of water existing on planets outside our solar system very low.”
The team came up with their new theory by using silicon isotopes as a metric to measure the mechanisms of planet formation and the time scales involved. By examining the isotopic composition of more than 60 meteorites and planetary bodies, the researchers were able to establish a connection between rocky planets like Earth and other bodies in the solar system.
The knowledge accumulated by scientists has led scientists to theorize that as reliance on chance diminishes, there is an increasing possibility that other planets have abundant water.
“This theory predicts that whenever you form a planet like Earth, you will have water on it,” said Martin Pizarro, a team member and Globe Institute professor. “If you go to another planetary system where there is a planet orbiting a sun-sized star, the planet should have water if it is at a decent distance.”
The research is described in a research paper published Wednesday (June 14) in the journal nature.
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