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Did Half of Earth’s Water Come From The Asteroids?

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Among the many mysteries of nature, the origin of water within the vast oceans on Earth had captured the imagination of mankind for centuries. Finally, we seem to have found an answer to this mystery thanks to the findings of a Japanese space mission named Hayabusa. In 2010, Hayabusa had completed its space odyssey of seven years and returned to earth with valuable data, images, and samples comprising small grains of rock from the asteroid Itokawa. Since then, the highly prized data, images, and samples are being studied by researchers from across the world.

Surprisingly, among the worldwide researchers, the ones from Arizona State University have recently discovered the presence of water in the grains of rock. This discovery has rekindled the debate over the provenance of water inside our vast oceans. The debate is related to whether the water came from the asteroids, comets or other sources. Researchers Maitrayee Bose and Ziliang Jin used a device called mass spectrometer to find the quantum of water present inside the grains, especially in a mineral called pyroxene. Why they choose the specific mineral for study? Well, the same mineral on earth often contains water.

The study brought out astonishing results. The pyroxene sourced from Itokawa not only contained water but its chemistry was similar to the water present on Earth. These findings were published on May 1, 2019 in a journal called Science Advances. Over the years, scientists have debated whether water on earth came from a cosmic hailstorm of asteroids or comets. The debate remained inconclusive so far as there were few physical samples from the asteroids to study.



Since Itokawa belongs to an asteroid belt that orbits between one third and three times the orbit of Earth, there is a possibility that many of the asteroids had hit our planet a long time ago. After accounting for the weathering, heating, and collisions encountered by Itokawa since aeons, both researchers came to the conclusion that asteroids like Itokawa might have filled half of the oceans on Earth. They further concluded that the rest of the water on Earth was formed from the minerals that were present during the formation of our planet.

Interestingly, successive missions like Hayabusa 2 and NASA’s OSIRIS-REx that are currently orbiting asteroids like Ryugu and Bennu respectively can bring more samples and add further credence to the evidence.

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