Wherever water flows on Earth, you can be sure to find life. This is why US space agency NASA’s motto in the hunt for alien life has been “follow the water.” And this search has just received a significant boost, following the shock discovery of water on an asteroid.
For the first time, evidence of water has been found in a rocky asteroid assumed to be bone-dry.
We didn’t really expect water to be there in Itokawa at all
Grains of dust from the asteroid Itokawa actually contain a surprising amount of water, following the latest analysis by Arizona State University cosmochemists.
Professor Maitrayee Bose, the study’s co-author, said: “We didn’t really expect water to be there in Itokawa at all.”
And scientists no believe if similar asteroids have similar amounts of water, such asteroids could have been a major source of water for early Earth.
Japanese spacecraft Hayabusa brought back more than 1,500 grains of Itokawa in 2010.
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Hayabusa: The 2010 JAXA asteroid mission has yielded a shock result (Image: JAXA)
Asteroid Itokawa: Surface patterns on one of the asteroid’s microscopic dust particles (Image: Arizona State University )
Asteroid Itokawa is a stony asteroid, known scientifically as an S-type, which indicates Asteroid Itokawa was born closer to the sun than to Jupiter.
Itokawa most likely formed from the rubble of a catastrophic impact that broke up a larger asteroid.
Most of Itokawa’s water would have evaporated away with the heat from that traumatic event as well as the asteroid’s proximity to the sun.
Earlier analysis has shown meteorites that break off from S-type asteroids are mostly dry – but Professor Bose decided to look for water anyway.
Arizona State University has an instrument called a NanoSIMS, capable of measuring one atom of hydrogen in 100,000 other types of atoms.
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And in two Itokawa grains, the scientists discovered approximately between 680 and 970 parts per million of water.
Earth’s crust, by comparison, contains 15,000 to 20,000 ppm of water.
Not only did Itokawa have water, it had the right kind of water to seed Earth’s oceans, the researchers found.
The grains’ ratio of deuterium, a heavy form or isotope of hydrogen, to the more common form of hydrogen matched the ratio found in earthly water.
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Asteroid Itokawa: The peanut-shaped asteroid has harboured an incredible secret (Image: JAXA)
Hayabusa: The JAXA craft returned from Asteroid Itokawa with 1,500 grains of dust (Image: Arizona State University )
Previous work has shown that icy comets, on the other hand, have the wrong deuterium ratio to explain Earth’s oceans.
But stony asteroids, like Itokawa, appear capable of fitting the bill.
Professor Bose added: “It is still dry with respect to anything in our human experience.
“But it is wet enough, and with the correct isotopic composition, for many such asteroids to provide half the water on Earth.”
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Professor Tomoki Nakamura of Tohoku University, who led the first team to study the Hayabusa samples, said: “This is very nice and careful work.
The Arizona State University researchers “proposed a new interpretation for the origin of water on the Earth.”
Professor Nakamura’s did however express concern as to whether water from Earth’s atmosphere could have contaminated the samples.
He would like to see the same analysis done on samples of Itokawa that were never exposed to the atmosphere, “although this sample preparation is extremely difficult,” he said.