Remnants of Large Rocky Extrasolar Body Contains Water

Scientists using data from NASA's Hubble Space Telescope and the Keck Telescope in Hawaii have stumbled upon evidence of water in the remnants of an extrasolar body orbiting a white dwarf star, marking the first time water has been discovered on a rocky body.

Researchers from the University of Warwick and the University of Cambridge analyzing the dust and debris around white dwarf star GD61 170 light-years away found that oxygen levels in the debris indicated it had once been part of a larger planetary body that was 26 percent water by mass (only 0.023 percent of the Earth's mass is water). They estimate that the water-rich body had a diameter of at least 56 miles.

"At this stage in its existence, all that remains of this rocky body is simply dust and debris that has been pulled into the orbit of its dying parent star. However this planetary graveyard swirling around the embers of its parent star is a rich source of information about its former life," professor Boris Gänsicke from the Department of Physics at the University of Warwick said.

"In these remnants lie chemical clues which point towards a previous existence as a water-rich terrestrial body. Those two ingredients — a rocky surface and water — are key in the hunt for habitable planets outside our solar system so it's very exciting to find them together for the first time outside our solar system."

Water is typically found in the atmospheres of gas giants or trapped as ice underneath the surface crust in most extrasolar planetary bodies. The discovery that GD61 once probably hosted a water-rich planet gives scientists even more hope in the search for a habitable exoplanet. The findings also indicate that habitable planets, including Earth, may get their initial supplies of water from rocky bodies such as asteroids.

"These water-rich building blocks, and the terrestrial planets they build, may in fact be common — a system cannot create things as big as asteroids and avoid building planets, and GD 61 had the ingredients to deliver lots of water to their surfaces," said lead author of the study Jay Farihi from the University of Cambridge's Institute of Astronomy.

You can read the full published study in the journal Science.