Because Mercury has little atmosphere, it lacks weather like as storms, clouds, winds, and rain. Its surface temperature may reach 801 degrees Fahrenheit during the day (because to its proximity to the sun) and -279 degrees Fahrenheit at night (because there is no atmosphere to trap the daytime heat).
However, geologists have discovered that there are active regions on Mercury that are responsible for major changes in its landscape. These regions are made up of hardened lava flows from volcanic eruptions millions of years ago.
These regions are called maria. The largest Maria is Marius Hills which reaches a height of 4,450 feet (1.35 kilometers). The other large Maria is Rima Mada which surrounds several large lakes.
In addition to these two marias, there are many small mare fields spread across Mercury. They are found near the planet's equator and contain lava that has solidified after cooling off rapidly from the hot lava flowing beneath its surface.
Marias can be seen from space using radar or visible light from Earth-based telescopes. However, because they are so far away, they appear as small points of light.
It is thought that the presence of these marian regions on Mercury's surface indicates that it had volcanoes once too. Although they are now frozen under hundreds of miles of ice, it is possible that they were once inhabited by humans.
Mercury's temperature ranges from 750 degrees Fahrenheit during the day to -300 degrees Fahrenheit at night due to the lack of an atmosphere. When it gets to be sunlight, the ice cover melts. Originally Answered: Why is there no cloud cover on Mercury? Because mercury does not contain water. Clouds are composed up of (typically) gaseous water. Without water, there can be no clouds.
However, this doesn't mean that it never receives rain. The most common weather phenomenon on Mercury is geysers. These are high-velocity jets of water and gas that shoot out of craters around the planet's equator. They can reach heights of over 300 feet and blast debris into space at more than 100 miles per hour.
The other major surface feature on Mercury is called a sulcus. These are long, narrow depressions in the surface sand or rock caused by the action of solar heat on the planet's thin veneer of air. The sun heats the top layer of the atmosphere, which rises and rushes down along the edge of the continent, causing cliffs and ravines where the sand or rock has been blown away.
Finally, lightning on Mercury is typically formed when two charged surfaces are close together. One side will usually be the ground, but it could also be another object with a charge. When these objects get close together, static electricity builds up on both objects, and then suddenly, they touch, and bang! A bolt of lightning shoots across the sky.
The sunny side is expected to reach temperatures of 750 to 800 degrees Fahrenheit, while the nighttime temperature drops to about -330 degrees Fahrenheit. Mercury's average temperature is 354 degrees Fahrenheit.
It gets very cold indeed at night on mercury. In fact, it's so cold that all the water on earth would freeze instantly if not for two things: heat is constantly flowing into and out of the planet, and there are large areas where ice does not form because there is no air around to blow away the heat.
The flow of energy into and out of Mercury is called its "thermal radiation." More heat is lost than received by the planet because a fraction of it is lost back to space. But even with this loss, Mercury has only 6 days and 19 hours when sunlight is directly overhead, so it must store up heat during the other half of its day to meet its annual demand.
As for the large areas of liquid water, they're found in two places: The first is an enormous ocean called Pan-Mercurian Ocean that covers most of the planet. The second is a set of small lakes called Mar's Sinkholes that appear as dark spots on some images of Mercury taken from space. These sinkholes are actually caves formed when lava flows blocked their exit, forming an underground chamber.