Scientists find water in Itokawa asteroid samples
Photo provided by JAXA, the Japanese space agency, showing the asteroid Itokawa, shaped like a peanut and approximately 550 m x 300 m in size. The asteroid was visited by Japan's Hayabusa space probe, which collected dust samples from its surface that scientists have now analyzed, discovering water molecules in what had been thought to be a bone-dry heavenly body. EFE/-EPAJAXA/Editorial Use Only/ No Sales/ Best Quality Available
Photo provided by JAXA, the Japanese space agency, showing two dust grains collected from the asteroid Itokawa, which was visited by Japan's Hayabusa space probe. In analyzing the dust samples from its surface, scientists discovered water molecules in what had been thought to be a bone-dry heavenly body. EFE/-EPA/Z. Jin and M. Bose/ASU-JAXA/Editorial Use Only/No Sales/Best Quality Available
A handout picture released by the Japanese Space Agency JAXA on Nov. 21 2005 shows the asteroid Itokawa, which was visited by Japan's Hayabusa space probe. EPA-EFE/JAXA HANDOUT EDITORIAL USE ONLY NO SALES
Washington, May 1 (efe-epa).- A group of researchers at Arizona State University has found water in samples collected from the surface of the asteroid Itokawa by Japan's Hayabusa space probe, according to a study published on Wednesday in the journal Science Advances.
This find, the authors say, suggests that impacts by similar asteroids early in Earth's history could have provided up to "half the water on Earth."
The asteroid is "still dry with respect to anything in our human experience," Maitrayee Bose, the study's co-author, said. "But it is wet enough, and with the correct isotopic composition, (for many such asteroids) to provide half the water on Earth."
Colleague Ziliang Jin, who headed the study, added that the samples they examined were relatively rich in water compared to the bone-dry average level of objects in the inner solar system.
The research team found between about 680 and 970 parts per million of water in two of the five Itokawa dust grain samples. Earth's crust, by comparison, contains 15,000 to 20,000 ppm of water.
The team also identified the mineral pyroxene in those two samples, which in terrestrial samples have water molecules within their molecular structure.
To study the samples brought back from the asteroid, each of them about half the thickness of a human hair, the team used a nanometer scale mass spectrometer (NanoSIMS) at ASU, which can measure the contents of these tiny mineral grains with great accuracy.
The NanoSIMS measurements revealed that the samples were unexpectedly rich in water, and the team also found that "normally dry" asteroids like Itokawa - where any liquid water long ago boiled away into the vacuum of space - could, in fact, contain more water than scientists has suspected.
Itokawa is a stony or Type S asteroid shaped somewhat like a peanut that is 550 meters (1,800 feet) in length by 300 m (985 ft.) in width orbiting the Sun every 18 months at an average distance of 1.3 astronomical units (AU), one AU being the distance from the Sun to the Earth.
Itokawa's orbit is elliptical, with its closest approach to the Sun being a little inside Earth's orbit and the farthest point on the ellipse being a little beyond the orbit of Mars.
Type S asteroids are some of the most common objects in the asteroid belt and originally they formed in a zone between 0.33 - 3 AU from the Sun.
The scientific team said that Itokawa is the remnant of a body at least 19 km (11.8 mi.) wide that at some time in the past was heated to between 537 C and 815 C (1,000 F to 1,500 F).
The primitive body suffered several huge shocks from impacts with other asteroids with a final event breaking it into smaller pieces, after which two of the rubble fragments eventually drifted together, fused and formed the strangely-shaped Itokawa some 8 million years ago.
Jin said that although the samples the team analyzed were collected on the asteroid's surface, they don't know where the grains were located in the original body. Nevertheless, their best estimate is that they were buried more than 100 meters (328 feet) below the surface before the final impact that broke that body into fragments.