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IIn a few days, a capsule containing soil samples from a distant asteroid will be released by a robotic spacecraft and dropped into Earth’s upper atmosphere. If all goes well, the container will parachute safely to the Woomera proving ground in South Australia on December 6, completing a mission that involved a three billion kilometer journey through our solar system.
The information returned could help solve several major astronomical puzzles, scientists say, including the mystery of the first appearance of water on our planet.
“Asteroids are the remaining building blocks of the formation of our solar system 4.6 billion years ago, and this makes them very important to science,” said Martin Lee, professor of planetary science at the University of Glasgow. “If you want to know what the planet was originally made of, you have to study asteroids.”
The Japanese probe Hayabusa 2 was launched six years ago and sent on a trajectory towards the asteroid Ryugu, which circles the sun every 16 months at a distance of between 90 million and 131 million miles. For 18 months, he surveyed this mass of primordial rock 1,100 meters wide before sinking close to its surface to collect a few balls of earth. Then the probe fired its ion thrusters and began its return to Earth for a year.
Lee and his colleagues will be among the first groups of scientists to study Ryugu soil samples when they are delivered – though the team won’t have much to work on. “We would expect to get only a few grains of material, each a few millimeters in diameter,” said geologist Luke Daly, a member of the University of Glasgow team. “However, we won’t really know how much we’ll earn until the Hayabusa capsule hits the bridge: slow, we hope.
Analyzing the composition of the surface of an asteroid from a few grains of soil seems ambitious. Nonetheless, the Glasgow team are confident. They plan to use a device called an atomic probe that allows researchers to identify individual atoms in a sample. Given the large number of atoms that make up even the smallest of samples, this will require counting and analyzing tens of millions of individual atoms.
“Essentially, we’re going to take a piece of earth and remove its outer surface with a laser,” Lee said. “In other words, we’re going to blow up its atoms, one by one. And then each of those atoms will be measured to determine the identity of that element and its particular isotope.
“We will also be able to reconstruct exactly where the atom was positioned in the sample, so we will get a three-dimensional image of the atomic structure of our sample.”
Engineers at Japan’s Jaxa space agency still don’t know how much material Hayabusa 2 has collected. Its predecessor mission, Hayabusa 1 – Hayabusa is the Japanese word for a peregrine falcon – in 2005, plagued with engine failures and other technical issues and brought back very little material from its target, the asteroid Itokawa. .
Hayabusa 2 is expected to bring in a lot more, although its samples will first have to survive when they return to Earth. This will begin when the probe releases a capsule carrying Ryugu earth. Entering the atmosphere at 27,000 mph, it will plunge toward Earth until, six miles above Australia, it deploys a parachute and glides toward the ground.
Samples will then be distributed to scientists around the world. “Besides telling us what the first solar system was made of, they will also tell us what happens to rocks when they are bombarded by the solar wind for billions of years – and this is of crucial importance to understanding the history of water in the solar system and, most importantly, on Earth, ”added Lee.
The solar wind is a flow of protons and other subatomic particles emitted by the sun. Earth’s atmosphere protects us, but in space, particles mercilessly strike surfaces that do not have such protection. “This bombardment can trigger the creation of water on the asteroids,” Daly added. “Protons are essentially hydrogen ions and could react with oxygen in rocks to create water molecules.”
Scientists are divided on the fundamental question of how water first appeared on our planet. Did it come along with all the other materials that made up our planet 4.6 billion years ago, or was it brought here much later by icy comets crashing into our planet?
Recent space probes – like the Rosetta mission which visited comet 67P / Churyumov – Gerasimenko between 2014 and 2016 – found water on these bodies. However, it is not quite like water on Earth. These extraterrestrial samples contain higher levels of deuterium, an isotope of hydrogen, than those found in Earth’s water and this has led many scientists to conclude that our supply must have been there from the start.
“However, it may be that these ancient comets were not the only source of water elsewhere in the solar system and that newer reservoirs were created by solar wind beating rocks at asteroids,” Lee said. .
“The water created there could have lower levels of deuterium, which would explain how our oceans have come to contain water with a different isotope signature. And, of course, studying the rocks atoms of the asteroid Ryugu, which has been blown by the solar wind for billions of years, may well give us the answer.
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