H2O found in "dry" asteroid samples brought to Earth over millions of kilometers by a brave probe • The Register

The withered itokawa hid water rides in his sleeve

Image of Itokawa taken by the Hayabusa probe. Image credit: JAXA

Two astronomers managed to find water in an asteroid sample from the Itokawa rock remnant, a type of asteroid previously thought to be dry.

JAXA, the Japanese space agency, visited Itokawa with its Hayabusa spacecraft in 2005. The bean-shaped asteroid is 1,800 feet long and 700 to 1,000 feet wide. It orbits the Sun every 18 months at an average distance of 1.3 times the Earth-Sun distance of 93 million miles.

Hayabusa fired tiny missiles on the surface of Itokawa to launch samples of rock dust from space to be transported to Earth. Five years later, the probe returned to our planet with its cosmic plunder. Five of the collected particles, measuring about half the thickness of a human hair, were donated to researchers at Arizona State University (ASU) in the United States. They then analyzed the dust for traces of water.

This is a strange gesture, given that Itokawa is categorized as stony or stony asteroids. These types of rocks reside in the inner vicinity of the solar system and consist of silicate materials and nickel-iron, previously thought to be waterless. The experiment, however, seems to have borne fruit since cosmochemists have found signs that the rock actually contains water.

"We found that the samples we examined were water-rich compared to the average of the internal solar system objects," said Ziliang Jin, the first author of the document published in Science Advances and a postdoctoral researcher at the University of Beijing. ;KNEW. The results revive the idea that asteroids could have provided half of the Earth's water while they crashed into the rocky surface of our original world.

The researchers found pyroxene in two of the five samples. These types of minerals have water molecules in their crystal structure. By measuring the amounts in the samples, the researchers estimated that the Itokawa mass originally contained between 698 and 988 parts per million (ppm) of water – one part per million representing one milligram of water per kilogram of water. Itokawa mass. Once they took into account the water losses due to heating and other processes, it is estimated that the asteroid contained about 160 to 510 ppm of water.

"The particles we analyzed came from a part of Itokawa called the Sea of ​​Muses," said Maitrayee Bose, co-author of the paper and assistant professor of Earth Exploration and Research. Space at the ASU. This is a smooth and dusty area on the asteroid. "

Itokawa itself is a smaller fragment of a larger asteroid, measuring 12 miles wide. The original rock was heated between 1,000 and 1,500 degrees Fahrenheit and shattered at one point after the collision with another asteroid. Two pieces then merged eight million years ago to become Itokawa.

"Although the samples were collected on the surface, we do not know where these grains were in the original parent body, but our best estimate is that they were buried more than 100 meters away. depth, "Jin said.

JAXA reports new asteroid samples. Its Hayabusa 2 probe has just extracted more dust from another Ryugu asteroid. ®

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