Mar 3, 2020 - Science

The Earth's gentle start

Illustration: Aïda Amer/Axios

The early Earth and other rocky planets may have formed quickly and gently, not violently through collapse and collision, as previously thought.

Why it matters: The details of Earth's formation are a long-standing mystery tied to how life may have arisen.

  • Specifics about planet formation are also key as scientists look out to other solar systems with worlds that might be habitable.

What's happening: A study published in Science Advances last week suggests that the proto-Earth may have hosted water before the Moon-forming impact occurred.

  • Other studies from NASA's New Horizons team found that Arrokoth — a world 1 billion miles past Pluto — also seems to have formed gently over time instead of quickly through collisions.

The big picture: Scientists think they have a pretty good understanding of how the giant planets like Jupiter and Saturn formed, but these new studies and years of research before them are forcing scientists to re-examine how rocky worlds like Earth, Mars and Mercury grew.

  • The gas giants likely formed by gobbling up pebbles, quickly becoming the dominant forces in their parts of the solar system.
  • Scientists are now trying to suss out the role this kind of growth may have played in the way that Earth and other small inner solar system worlds grew.

The intrigue: If Earth and other rocky worlds did grow through pebble accretion, it might have implications for when our planet was habitable.

  • "In principle, if we didn't have the Moon-forming impact, life could have formed much earlier on the Earth, probably," Martin Schiller, co-author of the Science Advances study, told Axios.

What's next: Scientists creating models of planetary formation are focusing on building our solar system from the ground up to test the various theories around how the inner planets — Mercury, Venus, Earth and Mars — formed.

  • Even if these rocky planets grew by pebble accretion, it's possible that dozens of protoplanets and asteroids that grew from that process collided in a violent cascade much in the same way that classical models show.
  • However, it's also possible that pebble accretion would have left the early inner solar system with just five objects — early Mercury, Venus, Earth, the Moon and Mars — with only one huge collision between the early Moon and Earth in the early solar system.
  • "It's really fun because we're reinvestigating all of the things that we had taken for granted and modeled in the past," planetary scientist Kevin Walsh told Axios.

Go deeper: A fingerprint of Earth from space

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Earth adopted a new "mini-moon"

Gemini Observatory's image of 2020 CD3. Photo: NSF/AURA/G. Fedorets

A likely "mini-moon" found orbiting Earth last month is moving away from our planet now, but it could be a harbinger of new small moons to come.

Why it matters: Objects like this one — which is thought to be a washing machine-sized asteroid captured by Earth's gravity — could allow scientists to one day study space rocks without needing to head all the way out to the asteroid belt.

Go deeperArrowMar 3, 2020 - Science

Iron rain on an alien world

Artist's illustration of the iron rain. Photo: ESO/M. Kornmesser

A telescope in Chile has found a world 640 light-years from Earth that rains liquid iron, adding to the strange tapestry of planets far from our own.

Why it matters: The more that scientists understand about planets circling other stars, the closer they get to finding out just how unique (or common) our solar system — and therefore life — is.

Go deeperArrowMar 17, 2020 - Science

NASA's next Mars rover is named Perseverance

Artist's illustration of the Perseverance rover on Mars. Photo: NASA/JPL-Caltech

NASA's next Mars rover, expected to launch to the Red Planet in July, is officially named Perseverance.

The big picture: Once on Mars, the mission is designed to search out possible signs of past life on the planet and cache samples for a future mission to return back to Earth one day.

Go deeperArrowMar 5, 2020 - Science