According to researchers study using the Herschel space telescope show that Comet Hartley 2 contains water more like that found on Earth than all the comets we know about. Just a few million years after its formation, the early Earth was rocky and dry, most likely, something brought the water that covers most of the planet today. The main candidates for the carriers of water, scientists have always considered the comet. Using HIFI, Heterodyne Instrument for the Far Infrared, scientists were able to measure isotope ratios in comet’s ice. Turned out that this ratio is 1,61 x10-4, while for the water on Earth, it is 1,59 x10-4, that is, rates are virtually identical.
The difference in the ratio of hydrogen isotopes in the last six studied comets and a comet Hartley, scientists explained immediately: all the studied earlier comets came from the Oort cloud, and the Hartley-2 came from the Kuiper belt. It means that the history of these objects and the conditions of their formation are different. If all the short-period comets are identical to Hartley-2 on the isotopic composition of water, it means that the main supplier of water in the Earth’s oceans were exactly a comets from the Kuiper belt.