Astronomy: Fragments of asteroid due to land in outback in 2020 thanks to Japan Aerospace Exploration Agency’s Hayabusa2. | The Canberra Times

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Pieces of an asteroid are currently hurtling through space towards the Earth. They’re headed straight for the Australian outback, and they’re due to land on Sunday, December 6. They’ve come from an ancient asteroid, older than the planets themselves, and in past eras, objects like it helped make the Earth into the living planet it is today. Those pieces of an asteroid are safely stored inside a spacecraft, the Japan Aerospace Exploration Agency (JAXA) Hayabusa2. If all goes to plan, their impact onto the Woomera Testing Range will be a gentle one. It will be the second time anybody has successfully returned a sample from an asteroid, and the first time one will be returned from an asteroid rich in water and the carbon-based building blocks of life known as organics. The target asteroid had been unmemorably named 1999 JU3, but it’s since been dubbed Ryugu, after a dragon’s underwater palace from Japanese folklore. In the story, a fisherman is taken to Ryugu by a turtle and returns with treasure from the ocean palace, much like Hayabusa2 from our asteroid. If it’s a palace though, it’s one in ruins. Ryugu appears to be a “rubble-pile” roughly 900m across, an assemblage of boulders only just holding itself together. Asteroids like it are thought to have originally been part of larger worlds formed from a mixture of ice and rock (i.e. mud), beyond the present-day asteroid belt. But if they formed all the way out there, what could they have to do with the Earth’s history? The gravity of the gas giants, Jupiter and Saturn, sculpts the orbits of objects around them like fingers in spinning clay, gathering clusters of tiny worlds here, emptying regions of space there. When the Solar System first formed, the orbits of the gas giants were still shifting and as they moved they flung many water-rich worlds into the inner planets. Exactly how much of the Earth’s water arrived this way is still debated, but it may well be that most of our oceans, clouds, and rivers owe their presence on Earth to asteroids like Ryugu. They also helped deliver the oily organics, that stuff that would become life, to the inner Solar System. In meteorites thought to be similar to Ryugu, organic chemicals as complex as amino acids can be found. MORE SPACE: That doesn’t mean life began on asteroids, but the ingredients of life as we know it were raining down on Earth, Mars, and Venus very shortly after they formed. The gas giants still fling rocks from the asteroid belt at us, although much less often these days. The giants squeeze asteroid orbits until they begin to pass close by the Earth, where they become known as near-Earth asteroids (NEAs) and, if they actually hit the Earth, then they’re called meteorites. Exactly where in the asteroid belt the different meteorite types come from is still an open question, but sample return missions like Hayabusa2 will help answer exactly that, helping us to build a geological map of the Solar System. Hayabusa2 is set to pass close by the Earth on December 6. It will jettison its sample return case, which will land in Woomera to be picked up by Japanese and Australian scientists. This treasure trove from Ryugu will reveal fascinating insights into the history of the Solar System, the Earth, and the beginnings of life itself.


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