Mercury gets burnt on one side by the scorching sun for extended periods of time, and it is so hot that lead melts. The opposite side is pitch black and bitterly cold. There's no vibe here. The surface resembles that of the moon, including rocks and craters. But while the moon's atmosphere protects it from certain types of radiation, Mercury is extremely vulnerable because it has no shield around it.
The darkness on Mercury is due to very thin air which moves rapidly across the planet's surface. This creates a lot of turbulence that blocks out sunlight. The only places on Mercury where you might see some light are at the bottoms of large craters or near volcanoes. Otherwise, you're completely in shadow!
Sunlight strikes the surface of Mercury about 48 times every day, more than any other planet except for Venus. Because Mercury is so close to the Sun, all points on its surface are always either directly exposed to the sun or in complete darkness. For this reason, scientists think that most of the planet was formed by volcanic activity. Large areas appear to be made up of smooth lava flows, while others have sharp peaks and valleys formed by intense volcanic activity.
Because Mercury has no atmosphere to protect it from solar radiation, it receives much stronger winds from the sun than does Earth. These gusts can reach 450 miles per hour or more at the equator.
Mercury's dark side is that it is extremely cold since it has practically no atmosphere to hold in heat and keep the surface warm. Temperatures can fall below -300 degrees Fahrenheit. The bases of several craters near Mercury's poles are never illuminated by sunlight. These areas are always dark.
The image above shows parts of two crater walls on the dark side of Mercury. You can see that one wall is much steeper than the other. This is because the rock under the surface is also different on this side of the planet. The composition of rocks on the dark side of Mercury is similar to that of ice, which is why it is so cold there.
However, even though ice is clear and doesn't contain any particles of dust or other substances that could reflect light, some parts of ice walls on Mercury have visible patterns called "glacial striations" which are caused by differences in temperature when the ice sheet that covered most of Canada and America moved over the continent many thousands of years ago.
These differences in temperature occurred because the route the ice sheet took as it moved over the land was not straight but rather wavy due to changes in the height of the land. As the ice sheet melted after it was removed its water drained into low spots leaving bare rock behind.
Mercury, along with Venus, Earth, and Mars, is a rocky planet. It, like our Moon, has a solid surface covered with craters. However, due to its proximity to the Sun, most of Mercury's surface is hot enough to melt ice and rock, which later flows into U-shaped valleys or even creates new land that rises above the surface.
Like the Moon, many large craters can be seen on Mercury. One of them is called Marius Hills. It is a group of three huge volcanoes formed when molten lava pooled in three separate places on the surface.
Another famous crater is Caloris. It was named after the classical god of fire because it looked like it had been formed by shooting flames from its rim. The space probe images also showed that parts of the floor of Caloris contain bright spots that may be volcanic vents.
There are other smaller craters as well. In fact, so far, scientists have identified more than 700 features on Mercury's surface that are at least 3 kilometers (1.9 miles) across or larger. Many of these features probably resulted from meteorite impacts over millions of years ago, but some may be signs of ongoing geologic activity today.