| Mercury |
| Mercury is the closest planet to the sun and the 8th largest (2nd smallest). It is smaller then Ganymeda and Titan but bigger in mass. It is the second major densest body in the solar system, after Earth. Mercury was named after the Roman messenger of the gods. That was probably because it moves so fast. Its average distance from the sun is 58 million-km. In many ways Mercury is similar to the moon. Both are heavily cratered and have no plate tectonics. Mercury is much denser then the moon though. Mercury's biggest crater is 1300 km wide! Mercury is often visible in the night sky with the naked eye. |
| Mercury has a very elliptical orbit. When it is the closest to the sun (Perihelion) its 46 million km away, and when it’s farthest from the sun (Aphelion) its 70 million km away. Until 1962, everyone thought Mercury's "day" and "year" was the same length. It was shown wrong though in that year. It is know that Mercury goes around the sun every 88 Earth days. Its day is 54 Earth days and 5 hours. Wow that's a long day! |
| Mercury has a very thin atmosphere. Because Mercury is so hot the atoms are quickly blasted into space, then they go into Venus and Earths atmosphere. So the atmosphere is constantly being replenished. Mercury's atmosphere contains sodium, helium, hydrogen and oxygen. Mercury's temperatures can vary from 427 degrees to -180 degrees Celsius. That's hot enough to melt tin. Venus is a bit hotter then this, but much more stable. |
| Mercury has no known moons |
| Mercury has no known rings |
| The planet Mercury has been known since the Sumerians (3rd millennium BC). It was given 2wo different names by the Greeks; Apollo as a morning star and Hermes as an evening star. Of course though it is the same body and Greek astronomers knew that. |
| Only one spacecraft has visited Mercury. Mainer10 flew by Mercury 3 times. Twice in 1974 and once in 1975. But only 45% of Mercury's surface were mapped. It is too close to the sun for the HTS to look at it. |
| Mercury is the second smallest planet. Only Pluto is smaller then it. That makes it the smallest terrestrial planets. Mercury's diameter is 4, 880 km. That makes it 1/3 the size of Earth! Its gravity is also 1/3 of Earth's. If Earth were a basketball, Mercury would be a golf ball. Wow that's a big difference! If you where on Mercury the sun would appear 3 times the size it does on Earth. |
 |
| Head of Mercury the winged messager |
 |
