NASA's mission to Mercury has discovered  the possibility of water ice on the planet. The Messenger spacecraft, which started its mission in 2011, has found craters of water ice and other volatile materials in Mercury's polar craters, which are permanently shadowed from the sun. The findings seem to support the theory  that water found its way onto early planets via ice meteorite bombardment. Translation: This is how the Earth got its supply of H2O.
"The new data indicate the water ice in Mercury's polar regions, if spread over an area the size of Washington, D.C., would be more than two miles thick," said  Messenger participating scientist David Lawrence. The next question that mission scientists are hoping that Messenger will answer is whether there are regions of Mercury, whose surface temperature is hot enough to melt steel, given the planet's proximity to the sun, which might contain both liquid water and organic compounds.
[Image via NASA]