Skip to main content

'Starter' Earth grew in a flash. Here's how the planet did it.

An illustration of the protoplanetary disk around our sun.
An illustration of the protoplanetary disk around our sun.
(Image: © Shutterstock)

Dust from meteorites that crash-landed on Earth have revealed that Earth's precursor, known as proto-Earth, formed much faster than previously thought, a new study finds. 

An analysis of this meteorite dust showed that proto-Earth formed within about 5 million years, which is extremely fast, astronomically speaking.

Put another way, if the entire 4.6 billion years of the solar system's existence were compressed into a 24-hour period, proto-Earth formed in just 1 minute and 30 seconds, the researchers said.

Related: Fallen stars: A gallery of famous meteorites

The new finding breaks with the previously held idea that proto-Earth formed when larger and larger planetary bodies randomly slammed into one another, a process that would have taken several tens of millions of years, or about 5 to 15 minutes in the fictional 24-hour timescale. 

In contrast, the new idea holds that planets formed through the accretion of cosmic dust, a process in which dust attracts more and more particles through gravity. "We start from dust, essentially," study lead researcher Martin Schiller said in a statement. Schiller is an associate professor of geochemistry at the Centre for Star and Planet Formation (StarPlan) at the University of Copenhagen's Globe Institute, in Denmark.

With accretion, millimeter-size particles would have come together, "raining down on the growing body and making the planet in one go," Schiller said. 

Schiller and his colleagues made the finding by studying iron isotopes, or different versions of the element iron, in meteorite dust. After looking at iron isotopes in different types of meteorites, they realized that only one type had an iron profile that was similar to Earth's: the CI chondrites, which are stony meteorites. (The "C" stands for carbonaceous and the "I" stands for Ivuna, a place in Tanzania where some CI meteorites are found.)

The dust in these CI chondrites is the best approximation out there for the solar system's overall composition, the researchers said. In the solar system's early days, dust like this joined with gas and both were funneled into a accretion disk orbiting the growing sun. 

Over the course of 5 million years, the solar system's planets formed. According to the new study, the proto-Earth's iron core also formed during this time, snatching up accreted iron from the proto-planet's mantle. Eventually, this proto-planet became the Earth we know today.  

Message from Mars

Meteorites from Mars tell scientists that, in the beginning, the composition of iron isotopes in the material making up Earth were different than they were later on. This likely happened because heat from the young growing sun altered them, the researchers said. 

After a few hundred thousand years passed, the area where Earth was forming became cold enough for unheated CI dust that came from farther away to become part of proto-Earth's accretion disc. 

Given that iron from this far away dust is found in Earth's mantle today, it makes sense that "most of the previous iron was already removed into the core," Schiller said. "That is why the core formation must have happened early."

The other idea — that Earth formed when planetary bodies randomly collided with one another — doesn't hold, he said. "If the Earth's formation was a random process where you just smashed bodies together, you would never be able to compare the iron composition of the Earth to only one type of meteorite," Schiller said. "You would get a mixture of everything."

The new finding may also apply to other planets in the universe, the researchers noted. In essence, this means that other planets may grow much faster than previously realized. In fact, there is already evidence that this is likely the case, according to data on thousands of exoplanets in other galaxies, said study co-researcher Martin Bizzarro, a professor at StarPlan.

"Now we know that planet formation happens everywhere," Bizzarro said in the statement. "When we understand these mechanisms in our own solar system, we might make similar inferences about other planetary systems in the galaxy."

This process may even explain when and how often water is accreted during planet formation.

"If the theory of early planetary accretion really is correct, water is likely just a by-product of the formation of a planet like the Earth," Bizzarro said. "Making the ingredients of life, as we know it, [is] more likely to be found elsewhere in the universe."

The study was published online Feb. 12 in the journal Science Advances

Originally published on Live Science.

  • TorbjornLarsson
    admin said:
    Proto-Earth was on a fast track to planet formation.

    'Starter' Earth grew in a flash. Here's how the planet did it. : Read more

    This seems fairly likely, see how they can robustly predict the isotope differences between Earth versus Mars and Vesta that formed further out and follows the Fe/Ca mixing line while Earth do not. It would be very hard to explain unless early core formation and late mantle contribution from pebbles in the Earth case. Formation within 5 Myrs would also explain why the inner planets have orbits in a plane while Mars from similar isotope results likely formed later and it, as well as the asteroid belt debris material, got stunted by the outer planets migration at 10 Myrs or so just as the protoplanetary disk dissipated/was dissipated https://advances.sciencemag.org/content/advances/6/7/eaay2338.full.pdf , https://www.sciencemag.org/news/2020/01/cataclysmic-bashing-giant-planets-occurred-early-our-solar-systems-history ]. That the protoEarth Tellus was hit by a Mars sized Theia planetesimal at 50 Myrs could have been a late result of that outer system upheaval, models of a glancing impact that would create Moon show that Theia material could have gone to the core.

    Quite a change from the picture a few years back, when Mars was believed to have formed much earlier, no one knew when Earth-Moon impact happened and the outer system migration was believed to have happened 3.9 billion years ago.
    Reply
  • CMAenergy
    admin said:
    Proto-Earth was on a fast track to planet formation.

    'Starter' Earth grew in a flash. Here's how the planet did it. : Read more
    The bible tells you the earth was formed in a moment of time, where he spoke and the earth was created.
    Science is slowly catching up !
    Read some more of the good book and you may learn something !
    Reply
  • TorbjornLarsson
    CMAenergy said:

    The bible tells you the earth was formed in a moment of time, where he spoke and the earth was created.

    Science is slowly catching up !

    Read some more of the good book and you may learn something !

    It's difficult to discern intent from a comment, so in case your comment lacked the /sarcasm tag on purpose:

    Erroneous superstition, especially obvious in the article context of millions of years formation process, and a good example why we know we cannot learn anything from freewheeling myth.

    Also, seeing how religiosity correlates well with dysfunctional societies and secularity with nations being better off, we know that the myth does not work to improve society (is "good"). For example:

    " Indicators suggest that the less religious nations are much better off. Average GDP per capita in the least religious countries is more than five times higher, while the unemployment rate is more than twice as low and the poverty rate is one and a half times lower. The homicide rate is five times lower. Life expectancy is 22 percent higher, and infant mortality is 1,000 percent lower — in part because the least religious nations spend 50 percent more per capita on health care. The least religious countries are also better educated, with a mean 12 years of schooling per capita vs. 7½ years in the most religious countries. Income inequality is 24 percent lower in the least religious countries, and gender inequality (as measured by the World Bank) is more than 400 percent lower. Finally, the least religious countries are freer, with an average score of 87.6 from Freedom House, compared to 56.5 for the most religious countries."

    https://www.washingtonpost.com/opinions/2020/02/19/william-barrs-america-vs-reality-2020/ ]
    Religiosity allows *1,000 percent more infant deaths*! That can't be "good" in anyone's summary of what it does.

    Remember:

    "Religion is an insult to human dignity. With or without it you would have good people doing good things and evil people doing evil things. But for good people to do evil things, that takes religion."

    - Steven Weinberg, Nobel Laureate

    https://en.wikiquote.org/wiki/Steven_Weinberg ]
    Reply