Water found on comet similar to that on Earth

Comet Hartley 2 has been found to have H₂O with proportions of deuterium (an isotope of Hydrogen) similar to that of our own oceans. This, compared with most comets which have double the fraction of this isotope, supports the theory that comets contributed to earth’s water as well as asteroid collisions in this planet’s creation. For more information visit http://www.nature.com/nature/journal/vaop/ncurrent/full/nature10519.html .