Some additional volatile ices such as ammonia may also be present.
This diversity was startling, as astronomers had expected KBOs to be uniformly dark, having lost most of their volatile ices to the effects of cosmic rays.
Comets are small Solar System bodies, typically only a few kilometres across, composed largely of volatile ices.
It probably wandered in from the outer belt-far enough from the sun that it was able to keep its volatile ices and organics-or else it's a comet core.
Similar features may be seen in ejecta blankets of Martian craters, suggesting impacts into a volatile (ice)-rich target material.
Extinct comets are those that have expelled most of their volatile ice and have little left to form a tail or coma.
The collision would have been violent enough to boil off volatile ices like methane but not violent enough to have destroyed either body.
Analysis of the magnitude and polarisation of the reflected signals suggested the presence of volatile ices, interpreted as including water ice, in the Moon's surface soils.
However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids.
Beyond the frostline volatile ices are generally more common.