Dwarf planet Ceres, the largest known object in the asteroid belt, was previously thought of as a lifeless and static rock. Observation made by NASA's Dawn spacecraft, however, suggest that like Earth, Ceres may have water cycles.
Ice On The Wall Of Juling Crater
Analysis of data from Dawn revealed that a crater wall on the dwarf planet became icier as the sun changed position in the sky over a six-month period. This finding suggests that subsurface ice particles may be lifted up into the air and then land on the wall of Juling crater like dews on Earth.
Researchers studied the infrared data from Dawn to find out how the ice was changing in the Juling crater as summer on Ceres began. The ice on the wall of the crater was observed to increase at the height of the warmest time on Ceres.
"We report the detection of water ice in a mid-latitude crater and its unexpected variation with time. The Dawn spectrometer data show a change of water ice signatures over a period of 6 months, which is well modeled as ~2-km2 increase of water ice," researchers wrote in their study, published in Science Advances on March 14.
Cycle Of Sublimation And Condensation On Ceres
Five sets of observations made over a period of six months suggest that the amount of exposed ice on the crater wall is increasing. The researchers said that this could be the result of small landslides that reveal ice from behind a dust layer and ice in the areas that are not usually hit by sunlight that got heated up, causing the water to sublimate into the air.
"The combination of Ceres moving closer to the sun in its orbit, along with seasonal change, triggers the release of water vapor from the subsurface, which then condenses on the cold crater wall. This causes an increase in the amount of exposed ice. The warming might also cause landslides on the crater walls that expose fresh ice patches," explained Andrea Raponi, from the Institute of Astrophysics and Planetary Science in Rome.
The sublimated ice is comparable to dew that evaporates in the heat of the day and then condenses on cool surfaces at night. Sunlight hitting the crater's bottom can turn ice into water vapor, which then condenses on the shadowed wall.
Carol Raymond, of NASA's Jet Propulsion Laboratory in Pasadena, California, said that this process has only been previously seen on comets, and it is surprising to see a cycle of sublimation and condensation on Ceres.
