Mercury Data Sheet
Color differences on Mercury are subtle, but they reveal important information about the nature of the planet's surface material. A number of bright spots with a bluish tinge are visible in this image taken by MESSENGER on Jan. 14, 2008, which is a mosaic from three different images.

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


Mercury has been known since ancient times. Its elusiveness generated the name Hermes, given by the Greeks, later translated to Mercurius by the Romans.