View of the asteroid Ryugu from the Hayabusa 2 spacecraft JAXA, University of Tokyo & collaborators© Provided by New Scientist
For the first time, researchers are working on analysing pristine gases from an asteroid. These gases were brought back in rock samples collected by Japan’s Hayabusa 2 spacecraft, which visited the asteroid Ryugu from 2018 through 2019, and they are giving us hints about how and where the asteroid – and other objects in the solar system – formed.
Ryugu was most likely formed toward the edges of our solar system before the migration of the giant planets flung it towards Earth. A new analysis of the iron in the samples shows that it may have come from even further out than researchers realised, near Uranus and Neptune, so these samples may help illuminate the history of the outer solar system.
“Essentially all of our knowledge of how we think the solar system formed and what this outer solar system material looks like is based on meteorites, but those have the disadvantage that they fell to Earth and were contaminated by air and weather and people,” says Henner Busemann at ETH Zürich in Switzerland, part of the research team that analysed the Hayabusa 2 samples. “In this case we know exactly where the sample came from, and it never touched the ground or saw rain.”
That means that we can use these samples to understand the asteroid and outer solar system in more detail. One of the ways researchers did that was by examining the gases that shook loose from the rock samples, but remained in the airtight sample containers, as they jostled their way back to Earth and determining how those gases got to Ryugu.
Because some of these gases got there directly from space radiation, this allowed the researchers to measure the age of the asteroid’s surface. “If you would walk on the asteroid, you would be exposed to all of these cosmic rays and the solar wind, and you would die of cancer very soon,” says Busemann. “The rocks, of course, do not die, but they undergo nuclear reactions that can tell us how long the rock has been exposed.”
While Ryugu itself – or at least the parent body that it broke off of long ago – is expected to be about 4.5 billion years old, the rocks in the sample were only at the surface for about 5 million years. That age is consistent with the amount of surface turnover seen in asteroids near Earth, not in the outer solar system, so Ryugu must have migrated inward from its birthplace at least millions of years ago.
Journal references:Science Advances, DOI:10.1126/sciadv.add8141,
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