Mercury Has Ice That Won't Melt
The closest planet to the sun, Mercury can experience daytime temperatures of more than 400°C. However, there are places on the planet where the sun cannot reach. Because Mercury's rotational axis has almost no tilt, its poles don't get direct sunlight, and the craters on those poles have freezing-cold depths. Water ice was found on the inner surfaces of these craters by the Messenger spacecraft. Scientist Sean C. Solomon told the New York Times that there could be upwards of 100 billion tons of ice on Mercury, enough to "encase Washington, D.C., in a frozen block two and a half miles deep."
from Crash Course
Key Facts In This Video
Mercury orbits the sun at an average distance of about 58 million km, roughly one-third of the distance from the Earth to the sun. (1:21)
A "year" on Mercury lasts about 88 Earth days, while a "day" lasts about 59 Earth days. (3:15)
The craters on Mercury are named after artists. (6:43)