What's the Latest Development?

During observations made with the powerful Herschel Space Telescope last year, astronomers found frozen water on a comet called Harltey 2. More recent analysis shows that the molecular composition of the comet's water—specifically, its deuterium-to-hydrogen ratio—matches that of Earth's. The Hartley 2 comet comes from the Kupiter belt, a band of space rocks much larger than our solar system's asteroid belt. Scientists will now look to other comets in the Kupiter belt to see if their composition is similar to Hartley 2. 

What's the Big Idea?

Water has been found on six comets prior to Hartley 2 but never before has the chemical composition of the water matched that of Earth's oceans. What's more, "the handful of water-bearing comets previously discovered, the researchers believe, came from the Oort cloud, a band of comets about a light-year away from the sun." The Kupiter belt, which scientists believe Hartley 2 calls home, is 1,000 times closer to Earth and could explain the difference in chemical compositions.