Half of Earths water may have come from ancient asteroid collisions The idea of an asteroid striking Earth is often positioned as a catastrophic event that would decimate all life on Earth. However, many scientists believe that asteroids can also help life flourish, delivering water to the planet billions of years ago.New research of samples from the peanut-shaped asteroid Itokawa, published in the journal Science Advances on May 1, suggest it harbored water, inferring that similar objects in the ancient, early solar system would have been the same and could have seeded the early Earth with life-sustaining water.In 2000 the Japanese Aerospace Exploration Agency, JAXA, sent the Hayabusa probe to the asteroid Itokawa in an attempt to grab samples from the space rock and bring them back to Earth. After an initial failed attempt,the probe was able to gather dust and return to Earth, landing in a remote region of outback Australia in June 2010. It was the first time asteroid samples had been brought back to Earth. Scientists have been studying the returned samples ever since, even showing us exactly what Itokawa looks like under the microscope.The research team, from Arizona State University, were gifted five incredibly tiny samples by JAXA, about a fifth the width of a human hair, and decided to hunt for water -- something that no other team was doing with the Itokawa samples."Until we proposed it, no one thought to look for water," said Maitrayee Bose, co-author on the paper, in a statement. "Im happy to report that our hunch paid off."Bose and lead author Ziliang Jin studied hydrogen isotopes and the water content in Itokawa, revealing the S-type (non-metallic) asteroid had similar levels of isotopes to those you would find in rocks on Earth. Although it is approximately 8 million years old (and its dust and soil is likely much older), the team found evidence that Itokawas samples were rich in water.The team hypothesize that their findings reveal an extraterrestrial origin for up to half of the Earths water, but caution that there is still more work to be done -- this is but the first example of an asteroid sample-return mission that has seen such a result."Sample-return missions are mandatory if we really want to do an in-depth study of planetary objects," Bose notes.The good news is two similar asteroid missions are currently in progress, with Hayabusas successor, Hayabusa-2, blowing a hole in asteroid Ryugu in an effort to extract samplesand return them to Earth in 2020. NASA are also running an asteroid study of the potentially-hazardous object known as Bennu, launching theOSIRIS-REx spacecraft in 2016 to high-five the asteroid and steal a handful of ancient dust. That spacecraft is scheduled to return in 2023.As such, fresh evidence for the origins of our planets most precious resource may be just around the corner.