 Surface water ice is unstable at distances less than 5 AU from the Sun , so it is expected to sublime if it is exposed directly to solar radiation . Water ice can migrate from the deep layers of Ceres to the surface , but escapes in a very short time . As a result , it is difficult to detect water vaporization . Water escaping from polar regions of Ceres was possibly observed in the early 1990s but this has not been unambiguously demonstrated . It may be possible to detect escaping water from the surroundings of a fresh impact crater or from cracks in the subsurface layers of Ceres . Ultraviolet observations by the IUE spacecraft detected statistically significant amounts of hydroxide ions near Ceres ' north pole , which is a product of water vapor dissociation by ultraviolet solar radiation . 
 Surface water ice is unstable at distances less than 5 AU from the Sun , so it is expected to sublime if it is exposed directly to solar radiation . Water ice can migrate from the deep layers of Ceres to the surface , but escapes in a very short time . As a result , it <a href='drop_aux' title='1'><mark>is</mark></a>difficult to detect water vaporization . Water escaping from polar regions of Ceres was possibly observed in the early 1990s but this <a href='been_done' title='2'><mark>has</mark></a> not been unambiguously demonstrated . It may be possible to detect escaping water from the surroundings of a fresh impact crater or from cracks in the subsurface layers of Ceres . Ultraviolet observations by the IUE spacecraft detected statistically significant amounts of hydroxide ions near Ceres <a href='null_genetive' title='3'><mark>'</mark></a>north pole , which <a href='drop_aux' title='4'><mark>is</mark></a>a product of water vapor dissociation by ultraviolet solar radiation . 
Surface water ice is unstable at distances less than 5 AU from the Sun , soo it is expected to sublime if it is exposed directly to solar radiation . Water ice can migrate from the deep layers of Ceres to da surface , but escapes in a very short time . As a result , it difficult to detect water vaporization . Water escaping from polar regions of Ceres was possibly observed in the early 1990s but this done not been unambiguously demonstrated . It may b possible to detect escaping water from the surroundings of a fresh impact crater or from cracks in the subsurface layers of Ceres . Ultraviolet observations by tdaIUE spacecraft detected statistically significant amounts of hydroxide ions near Ceres  north pole , which a product of water vapor dissociation by ultraviolet solar radiation .