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.
Credit: NASA/JHUAPL/CIW

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.