Name
|
- Mercury was the ancient Roman god of commerce and travel, and the
planet was likely given this name because of its swift movement across
the sky and the transient nature of its appearance.
|
Discovery
|
- Mercury has been known since ancient times, and its observation has
been documented since at least 3000 BC, in texts of the ancient
Sumerians.
|
Size & Mass
|
| Diameter |
4,880 km |
38% of Earth |
| Mass |
3.3 x 1023
kg |
5.5% of Earth |
| Escape
velocity |
4.3 km/s |
38% of Earth |
| Gravity |
3.8 m/s2 |
39% of Earth |
| Density |
5.4 g/cm3 |
98% of Earth |
- Mercury is among the smallest of the planets (with only Pluto
being smaller), and is in fact smaller than several moons in the
solar system.
|
|
Orbit
|
| Radius |
57,900,000 km [average] |
0.39 AU
[average] |
| Eccentricity |
0.21 |
|
| Inclination |
7° |
|
| Revolution |
88.0 days |
|
| Velocity |
48 km/s |
|
| Obliquity |
0° |
|
| Rotation |
58.7 days |
|
- Mercury has a highly eccentric orbit, ranging from 46-70
million kilometers from the Sun.
Small variations in Mercury's orbit, observed in the 1800's,
were later explained by Einstein's General Theory of Relativity.
|
|
Appearance
|
| Magnitude |
-0.42 |
|
| Angular
size |
4.5' to 13' |
|
| Albedo |
0.12 |
|
- Mercury is easily seen with the naked eye, but its close
proximity to the Sun limits viewing opportunities. It can
only be seen within about 45 minutes of sunrise or sunset, and
even then these opportunities exist only when Mercury is near
its greatest angular distance from the Sun as viewed from Earth.
|
|
Conditions
|
| Temperature |
100 K to 700 K |
|
| Atmosphere |
virtually none |
| Appearance |
Heavily cratered and
fractured |
| Features |
Largest feature is the
Caloris Basin (a 1,300 km wide impact crater) |
- Mercury's surface temperature has the largest range of any in
the solar system, primarily because it has virtually no
atmosphere to buffer the transition between day and night.
|
|
Moons/Rings
|
- Mercury has no moons or rings.
|
Exploration
|
|
Interesting Facts
|
- Radar observations of Mercury show evidence of ice in the permanent
shadows of some craters near the north pole!
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Links
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