Asteroid science rewrites the history of the solar system

Illustration: Sarah Grillo/Axios

New studies, missions and rich data on asteroids give scientists a more accurate picture of the history of the solar system.

Why is this important: Asteroids are leftovers from the dawn of the solar system that carry a record of the materials that built the planets. They could help understand how the solar system formed – and how life-giving water arrived on earth.

  • These space rocks can also threaten our planet, and while strikes are rare, scientists stress that understanding these objects is key to keeping Earth safe.

Driving the news: A trio of papers published today analyzed samples from the asteroid Ryugu returned to Earth in 2020 by the Hayabusa2 spacecraft.

  • Scientists have found new evidence that the asteroid’s parent formed on the far outskirts of the solar system, offering potential clues to Earth’s history.

How it works: The composition of asteroids is studied by analyzing meteorites that fall to Earth or more pristine samples taken from the asteroids themselves. Previous analysis of samples from Ryugu revealed that the asteroid’s minerals and chemicals are similar to those of a type of meteorite (CI chondrites) formed in the outer solar system.

  • But just because the asteroid and the CI chondrites formed from the same materials doesn’t mean they necessarily formed in the same place, says Timo Hopp, a scientist at the Max Planck Institute for Earth Research. solar system and co-author of two of the new papers.
  • Materials move through the solar system – and understanding when, where and how is key to unraveling Earth’s history.
  • Isotopes, or types of elements, in an asteroid or meteorite are fingerprints indicating where materials formed and can be used to chart their way through the solar system.

Details: In the new papers, international teams of scientists measured the abundance of noble gases, including helium and neon, in samples from Ryugu as well as the asteroid’s element isotopes.

  • They found Ryugu is rich in volatile gases, which could help scientists understand how volatile gases were first delivered to Earth, where they played a key role in forming the planet’s vital atmosphere.
  • Another one recent study from the zinc content of the meteorites found, the origin of the Earth’s volatile elements comes, in part, from the outer solar system.

Iron isotopes found in Ryugu and CI chondrites are distinct from those found in other meteorites that formed in the outer solar system, suggesting that they formed in a different reservoir farther from the Sun, according to one of the studies.

  • Other meteorites are thought to come from asteroids formed in the same nursery as Jupiter and Saturn.
  • But the compositions of Ryugu and the CI chondrites suggest that their predecessors originated elsewhere, possibly near Uranus and Neptune, the authors write.
  • They then moved one way or another from the edge of the solar system to the surface of the Earth.

The plot: The findings also mean that Ryugu and CI chondrites may “share a common heritage with Oort cloud comets”, write the authors. The Oort cloud is a massive layer of ice and dust 4.6 trillion kilometers from the Sun and right under the Sun’s gravity.

  • It’s a “tempting” idea, says Kevin Walsh, a Southwest Research Institute scientist who studies asteroids.
  • Comets are considered to be the most primitive bodies in the solar system. If some asteroids were to end up blasted to the outskirts of the solar system where they formed comets, “that would be a big key for us to unlock understanding of the dynamic history of the solar system,” Walsh said.

Yes, but: The amount of carbon in the samples from Ryugu suggests that its parent body did not form from comets, according to a published article last month.

  • Hopp says the properties of comets are different from those of Ryugu and other asteroids, but that may be because they have changed since they formed and passed through the solar system.
  • One challenge is that there is not much data on comets. A mission to return comet samples from the Oort Cloud is likely not possible in our lifetimes, Hopp says.
  • Instead, they propose to recover samples of asteroids that may have formed in the Kuiper Belt beyond Neptune.

The big picture: Knowing more about the composition of asteroids is not just about understanding the history of the solar system.

  • Knowing the composition of asteroids in Earth’s neighborhood is key to determining the best way to deflect them should one ever be found on a collision course with Earth.
  • Scientists believe that some asteroids are metal-rich and dense, while others are actually piles of loose rock rubble floating together in space.
  • The means of deflecting an asteroid can change depending on its composition.

Between the lines: The successful DART spacecraft deflected an asteroid recently, but researchers still have a lot to learn about how best to deflect an asteroid if necessary.

  • A new tool developed by MIT researchers could help map the interiors of asteroids, making it easier to find the most effective way to steer them off course.
  • “If you know the density distribution of the asteroid, you can hit it in the right place to make it actually move away,” said Jack Dinsmore, who helped develop the tool. statement.

What to watch: NASA’s OSIRIS-REx spacecraft is expected to return a sample from another asteroid to Earth in September 2023, which will give scientists clues to the variety of asteroids and compositions that exist in the solar system.

  • NASA was also due to launch another asteroid mission this year to the strange asteroid Psyche – believed to be the iron core of a long-dead planet – but technical problems have delayed. It is unclear when, or if, the mission will take off.

Go further: Asteroids help trace the journey of water through the solar system

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