#cosmochemists; #NanoSIMS; #ArizonaStateUniversity
Arizona (U.S.), May 2 (Canadian-Media): Two cosmochemists at Arizona State University have made the first-ever measurements of water contained in samples from the surface of an asteroid. The samples came from asteroid Itokawa and were collected by the Japanese space probe Hayabusa.
Original morphology of the two studied Itokawa particles. Image Credit: Japan Aerospace Exploration Agency (JAXA), edited by Z. Jin
The team's findings suggest that impacts early in Earth's history by similar asteroids could have delivered as much as half of our planet's ocean water.
"We found the samples we examined were enriched in water compared to the average for inner solar system objects," says Ziliang Jin. A postdoctoral scholar in ASU's School of Earth and Space Exploration, he is the lead author on the paper published May 1 in Science Advances reporting the results. His co-author is Maitrayee Bose, assistant professor in the School.
"It was a privilege that the Japanese space agency JAXA was willing to share five particles from Itokawa with a U.S. investigator," Bose says. "It also reflects well on our School."
The team's idea of looking for water in the Itokawa samples came as a surprise for the Hayabusa project.
"Until we proposed it, no one thought to look for water," says Bose. "I'm happy to report that our hunch paid off."
In two of the five particles, the team identified the mineral pyroxene. In terrestrial samples, pyroxenes have water in their crystal structure. Bose and Jin suspected that the Itokawa particles might also have traces of water, but they wanted to know exactly how much. Itokawa has had a rough history involving heating, multiple impacts, shocks, and fragmentation. These would raise the temperature of the minerals and drive off water.
To study the samples, each about half the thickness of a human hair, the team used ASU's Nanoscale Secondary Ion Mass Spectrometer (NanoSIMS), which can measure such tiny mineral grains with great sensitivity.
The NanoSIMS measurements revealed the samples were unexpectedly rich in water. They also suggest that even nominally dry asteroids such as Itokawa may in fact harbor more water than scientists have assumed.