Mercury is one of the hottest places in the solar system. Daytime temperatures at its equator can reach 800 degrees Fahrenheit — hot enough to melt lead. But it also has some cold spots. In fact, they may be so cold that they hold huge deposits of ice — billions of tons of it.
Mercury is the closest planet to the Sun, so it makes sense that it would get hot. But the planet doesn’t have an atmosphere, so the heat isn’t distributed around the planet. At the poles, where the Sun is always quite low in the sky, temperatures can be hundreds of degrees below zero.
It’s especially cold inside deep craters, where the Sun never shines at all. Radio telescopes on Earth, as well as instruments on a Mercury orbiter, found evidence of water ice inside some of those craters. They also found evidence of ice between the craters, buried under layers of dirt.
It’s not certain where the ice came from. It might have been deposited when water-bearing asteroids or comets slammed into Mercury. Or it could have come from ice volcanoes on the planet itself. Regardless of its origin, though, there’s a lot of ice on this hot little planet.
Mercury is in view shortly after sunset right now, quite low in the west-northwest. It looks like a bright star, but it’s so low in the twilight that it’s hard to spot. It’s a little easier to see this evening, though, because the planet is close to the right of the Moon.
More about the Moon and planets tomorrow.
Script by Damond Benningfield