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Asteroids and comets seed exoplanets with water

Earth’s water likely came from asteroids and/or comets. New research suggests that small bodies in distant solar systems carry water to their planets, too.

Artist’s impression of a rocky and water-rich asteroid being torn apart by the strong gravity of the white dwarf star. Similar objects in the solar system likely delivered the bulk of water on Earth and represent the building blocks of the terrestrial planets. Image credit: Mark A. Garlick / University of Warwick

Artist’s impression of a rocky and water-rich ‘exo-asteroid’ being torn apart by the strong gravity of a white dwarf star. Similar objects in our solar system likely delivered the bulk of Earth’s water, creating conditions suitable for life to emerge. Image via Mark A. Garlick / University of Warwick

A new study, published today (May 7, 2015) in Monthly Notices of the Royal Astronomical Society suggests that water delivery via asteroids or comets is likely happening in many other planetary systems, just as it happened on Earth. The research adds support to the idea that the same process that created a suitable home for life in our solar system also occurs in distant planetary systems.

Dr. Roberto Raddi, of the University of Warwick’s Astronomy and Astrophysics Group is the lead researcher. Raddi said:

Our research has found that, rather than being unique, water-rich asteroids similar to those found in our solar system appear to be frequent. Accordingly, many planets may have contained a volume of water, comparable to that contained in the Earth.

It is believed that the Earth was initially dry, but our research strongly supports the view that the oceans we have today were created as a result of impacts by water-rich comets or asteroids.

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In observations obtained at the UK William Herschel Telescope in the Canary Islands, the University of Warwick astronomers detected a large quantity of hydrogen and oxygen in the atmosphere of a white dwarf star (known as SDSS J1242+5226). The quantities found provide the evidence that a water-rich exo-asteroid – an asteroid outside our solar system – was disrupted and eventually delivered the water it contained onto the star.

The asteroid, the researchers concluded, must have been comparable in size to Ceres, which, at more than 1,400 miles (900 km) across, is the largest asteroid in our solar system. Dr. Raddi said:

The amount of water found in SDSS J1242+5226 is equivalent to 30-35% of the oceans on Earth.

The impact of water-rich asteroids or comets onto a planet or white dwarf results in the mixing of hydrogen and oxygen into the atmosphere. Both elements were detected in large amounts in SDSS J1242+5226.

Research co-author Professor Boris Gänsicke, also of University of Warwick, explained:

Oxygen, which is a relatively heavy element, will sink deep down over time, and hence a while after the disruption event is over, it will no longer be visible.

In contrast, hydrogen is the lightest element; it will always remain floating near the surface of the white dwarf where it can easily be detected. There are many white dwarfs that hold large amounts of hydrogen in their atmospheres, and this new study suggests that this is evidence that water-rich asteroids or comets are common around other stars than the sun.

Artist's concept via DailySciencejournal.com

Artist’s concept via DailySciencejournal.com

Bottom line: Research published May 7, 2015 in Monthly Notices of the Royal Astronomical Society suggests asteroids and comets in distant solar systems likely contain large amounts of water. The research adds support to the idea that the same process that created a suitable home for life in our solar system also occurs in distant planetary systems.

Read more from the University of Warwick

Eleanor Imster

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