More Information on the Planet Mercury
The innermost planet is rarely seen because of the Sun's glare. With less than half Earth's gravity, Mercury retains only a wisp of an atmosphere (presumed to be helium). The lack of a significant atmosphere allows temperatures to fluctuate from 750 degrees Fahrenheit during the day to minus 320 Fahrenheit at night.
Like the other terrestrial planets — Venus, Earth and Mars — Mercury is made mostly of rock and metal. This small world is scarred by craters and looks somewhat like our Moon.
Mercury data (averages):
Diameter: 3,031 miles
Time to rotate: 58.6 days
Orbit: 88 Earth days
Compared to Earth:
Mass: 5.5% of Earth's
Diameter: 38% of Earth's
Distance from Sun: 47% as far
MERCURIUS: ROMAN WINGED MESSENGER OF THE GODS
Mercury has been known since ancient times. Its elusiveness generated the name Hermes, given by the Greeks, later translated to Mercurius by the Romans.