I amIn a few days, a capsule containing soil samples from a distant asteroid will be dropped by a robotic spacecraft and dropped into Earth’s upper atmosphere. If all goes well, the container will parachute safely on the Woomera test range in South Australia on 6 December, completing a mission that includes a trip of three billion miles into our solar system.
Scientists said the returned information could help solve many big astronomical puzzles – including the mystery of how water first came to our planet.
Martin Lee, a professor of planetary science at the University of Glasgow, said, “Asteroids are the building blocks left over from the formation of our solar system 4.6 billion years ago and that makes them very important for science.” “If you want to know what the planet was initially made of, you need to study asteroids.”
The Japanese probe Hayabusa 2 was launched six years ago and sent the asteroid Ryugu into the trajectory, which orbits the sun every 16 months at 90 million to 131 million miles. For 18 months, it surveyed a 1,100-yard-wide lump of primordial rock before it snapped close to its surface to collect some scoops of clay. The probe then fired off its ion thrusters and began its year-long return to Earth.
Ryugu will be one of the first groups of scientists to study soil samples when distributed to Lee and his colleagues – although there won’t be much to work on the team. “We expect only a few grains of material, a few millimeters in diameter,” said geologist Luke Daly, a member of the Glasgow University team. “However, we won’t really know how much we’ll get until the Hayabusa capsule hits the deck: slowly, we hope.”
The analysis of the surface structure of the asteroid with some clay spots seems ambitious. Nevertheless, the Glasgow team is confident. They plan to use a device called an atomic probe that allows researchers to identify individual atoms in a sample. Given the vast number of atoms that make up the largest part of the sample, this would require counting and analyzing atoms of millions of individuals.
“Essentially, we’ll take a piece of clay and terminate its outer surface with a laser,” Lee said. “In other words, we will explode its atoms one by one. And then each of these atoms will be measured to determine the identity of that element and its particular isotopes.
“We will also be able to recreate exactly where the atoms were positioned in the sample. So we will get a three-dimensional image of the atomic structure of our sample.”
Engineers at the Japanese space agency Jaxa are still unsure how much material Hayabusa 2 has collected. Its predecessor mission, Hayabusa 1 – Hayabusa is the Japanese word for a perigreen hawk – in 2005, suffered from engine failures and other technical problems and brought back much less material from its target, the asteroid Pokawa.
Hayabusa 2 should be brought back more, although its samples must first avoid their return to Earth. This will begin when the probe releases a capsule carrying soil from Rayugu. Entering the atmosphere at 27,000mph, it will plunge towards the Earth until, six miles above Australia, it will deploy a parachute and glide to the ground.
The samples will then be distributed to scientists around the world. “In addition to telling us what the early solar system is, they will also tell us what happens to rocks when bombarded by solar wind for billions of years – and it makes a significant impact in understanding the story of water. Solar system and, most importantly, on Earth, ”Lee said.
Solar wind is a stream of protons and other sub-atomic particles emitted by the Sun. Earth’s atmosphere shields us, but there is a re-transformation of particles in space that lack such protection. “This bombing could trigger water buildup on asteroids,” Daly said. “Protons are, essentially, hydrogen ions and can react with oxygen in rocks to form water molecules.”
Scientists are divided on the basic question of how water first appeared on our planet. Has it come with all the other materials that our planet formed 4.6bn years ago or was it brought here after being crashed by icy comets on our planet?
Recent space probes – such as the Rosetta mission, which visited Comet 67P / Churyumov – Gerasimenko between 2014 and 2016 – have found water on these bodies. However, it is not quite like water on Earth. These extraterrestrial samples contain a high level of deuterium, an isotope of hydrogen, found in water from the Earth and have led many scientists to conclude that our supply must have been here from the beginning.
“However, it may be that these ancient comets have not been the only sources of water from elsewhere in the solar system and more recent reservoirs have been formed by solar wind-moving rocks on the asteroids,” Lee said.
“Deuterium levels can be reduced by the creation of water, and this will explain how water came into our oceans with a different isotope signature. And, of course, studying atoms from the rocks of the asteroid Rayugu, which have been eroded by the solar wind for billions of years, may well answer us. “