Ceres has been the source of much mystery for astronomers studying the asteroid belt between Mars and Jupiter, but NASA’s Dawn mission has been crucial in shedding light on the strange dwarf planet. According to a report from UPI, the Dawn probe has mapped all of the craters on Ceres that remain shrouded in permanent shadows.

Scientists say that ice has likely been accumulating in the craters on Ceres for nearly a billion years. The newly mapped craters may hold some of the oldest ice samples within our immediate reach, which could provide invaluable insights into the conditions of the solar system a billion years ago.

According to a statement from Norbert Schorghofer, a scientists from the University of Hawaii at Manoa and guest researcher with the Dawn Mission, “Ceres has just enough mass to hold on to water molecules, and the permanently shadowed regions we identified are extremely cold – colder than most that exist on the moon or Mercury.”

The secrets of Ceres and thus, the solar system, are trapped at the bottom of the crater pits on the surface of the dwarf planet. These “cold traps” have never seen the sun’s direct light, and preserve ice from a significantly different time in the solar system. The largest cold trap mapped by Dawn lies at the bottom of a crater measuring 10 miles wide.

The findings of the Dawn probe reveal that Ceres has roughly 695 square-miles of terrain that has never seen the sun’s light, which is less than one percent of the surface area of the dwarf planet’s entire northern hemisphere.

Researchers believe that roughly one out of every thousand water molecules originating on Ceres takes its final resting place in the form of ice in one of its cold traps. Researchers hope to continue studying the dwarf planet in hopes of learning more about the way water behaves elsewhere in space.

A NASA press release describing the details of the study can be found here.