A recent study by NASA is forcing scientists to reconsider long-held beliefs of Mars.

NASA's study revealed that water, which once entirely covered Mars, has never left the planet's atmosphere but rather taken a different form.

Scientists originally thought a weak magnetic field allowed solar winds to gradually strip away the water from Mars' atmosphere, but data suggests otherwise.

A big factor in the new thinking is that the water did not leave but rather shifted its form is the existence of deuterium. Deuterium is a "version of hydrogen with both a proton and a neutron, instead of a single proton as is the case with most hydrogen atoms."

NASA's researchers suggest the hydrogen did not escape Mars' atmosphere but is trapped in the minerals that comprise Mars' crust. Unlike earth, where trapped hydrogen escapes minerals through volcanic activity, the hydrogen trapped in minerals on Mars has no way to escape.

NASA explained this by saying, "When water interacts with rock, chemical weathering forms clays and other hydrous minerals that contain water as part of their mineral structure. This process occurs on Earth as well as on Mars. On Earth, old crust continually melts into the mantle and forms new crust at plate boundaries, recycling water and other molecules back into the atmosphere through volcanism. Mars, however, has no tectonic plates, and so the “drying” of the surface, once it occurs, is permanent."

Photo credit: BGR.com