Mercury is a fairly interesting planet as it is the closet to the Sun and suffers because of it. Being so close its surface endures greater temperature extremes than any other body in the Solar System, with some regions cold enough to freeze water, if any is there. Well researchers from the University of California, Los Angeles and MIT have determined that there is indeed water ice on the air-less planet, hiding where the Sun does not shine.
Due to the tilt of Mercury's axis and numerous impact craters, there are many areas that sunlight never heats, so if water were to get there, it would remain. In the 1990's, radar telemetry suggested there may be ice there, but now thanks to the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) probe, equipped with a sensor built at NASA's Goddard Space Flight Center, it has been confirmed, and more. The sensor is an altimeter that fires a laser at the surface to measure the distance to the satellite and by analyzing how bright the reflection is, the researchers could find where water ice was on the surface. They also found nearby patches that were darker than expected, even for the already dark Mercury. After developing a heat model for the planet though, the researchers realized the darker regions are likely from an organic material that is actually resting on top of frozen water.
Now that we know there is indeed water ice on Mercury, the next question is how did it get there? Likely it, like other volatile that would normally be boiled off, came from asteroids, comets, and the like that impacted the planet's surface. If this is the case then the organic material insulating some of the ice may have arrived by the same method.