Temperatures at the dark craters of the north pole of Mercury can dip to
as low as 370 degrees below zero.
Image: NASA/Johns Hopkins University Applied Physics Lab/Carnegie Institution of Washington
There's Ice in Mercury
Of all the planets in the Solar System, Mercury is the closest to the sun. You'd naturally think that it's also the hottest, but it's not (that distinction belongs to Venus). Oh, no doubt Mercury can get quite hot - its surface temperature can reach up to 800 °F, but at the poles, its temperature never gets above freezing. That's where NASA's Messenger Spacecraft found a large volume of water ice - estimated to be 100 billion to 1 trillion tons of ice, actually.
Maat Mons, the highest volcano on Venus. Image: NASA/JPL
It Snows Metal on Venus
Snowcapped mountains on Earth are majestic, but they're by no means unique in our Solar System. Venus has its own snowcapped mountains, but instead of water, the "snow" is made of heavy metals like lead sulfide (galena) and bismuth sulfide (bismuthinite).
Olympus Mons on Mars. Image: NASA/JPL
Mars has the Tallest Mountain in the Entire Solar System
Let's skip Earth for now and head on over to Mars. If you think our Mount Everest is tall, check out the Olympus Mons on the Red Planet. At about 14 miles (22 km) tall, it's three times as tall as Mount Everest's height above sea level. It's pretty big, too. Olympus Mons is approximately the size of Arizona.