GD 61

In 2013, a circumstellar disk that resulted from the destruction of a water-rich asteroid was detected in close orbit around GD 61, which makes this the first detection of solid or liquid water on an extrasolar body. This asteroid would originally have been 26% water by mass, close to the water content of Ceres. This evidence suggests that a planet, with a rocky surface similar to Earth's, may have existed in the past, with the asteroid thus being an artifact from this period, now possibly part of a debris field from the hypothetical planet's breakup. Such a planet would have had both a rocky surface and water, two key ingredients for life. The researchers used the Cosmic Origins Spectrograph on the Hubble Space Telescope to determine the elemental composition. The elements magnesium, silicon, iron, and oxygen were detected, all components of rocky planets, although the levels of oxygen were much higher than what could be accounted for. The lack of associated carbon left only one candidate for the oxygen excess—water.