Researchers used the Hayabusa probe to conduct the first water sample measurements of an asteroid, with the spacecraft retrieving 1,500 water particles from the asteroid Itokawa. This is not the only asteroid-studying mission by Japan. Japan also runs another mission called Hayabusa 2 which also has a sample return mission, although from the asteroid Ryugu. As well, NASA’s OSIRIS-REx surveys the large asteroid Bennu, as carbon-rich asteroids have also greatly contributed to life as we know it on Earth.
A study detailing the analysis of five of the particles from the asteroid samples was published Wednesday in the journal Science Advances. The samples were collected from an area on Itokawa known as the Muses Sea, which is smooth and dusty.
“We found the samples we examined were enriched in water compared to the average for inner solar system objects,” Ziliang Jin, lead study author and postdoctoral scholar at Arizona State University’s School of Earth and Space Exploration said in a statement.
Researchers didn’t intend to study water samples in the asteroids until Jin and another researcher from Arizona State University, Maitrayee Bose, proposed the idea. Researchers knew that Itokawa is an S-type asteroid which is one of the most common types of asteroids found in the asteroid belt.
“They originally formed at a distance from the Sun of one-third to three times Earth’s distance,” Bose said.
Itokawa has a peanut shape and orbits the sun every 18 months, it passes through Earth’s orbit and then goes beyond Mars. It measures 1,800 feet long and between 700 and 1000 feet wide.
According to the researchers two fragments called lobes merged 8 million years ago, with researchers believing that those samples got buried 328 feet inside a parent body which was much larger and that then broke apart. Once the asteroid broke apart, the samples were exposed to radiation, but they still contained water, whereas the minerals are quite similar to those found on Earth.
“This means S-type asteroids and the parent bodies of [non-modified asteroids] are likely a critical source of water and several other elements for the terrestrial planets,” Bose said. “That makes these asteroids high-priority targets for exploration.”
According to the two researchers, water samples in the asteroid suggest that impacts on early Earth throughout its history could have brought as much as half of the ocean water contained in the planet today, and water is known to be one of the key features of a planet to sustain life as we know it today.