Mercury: Facts & Figures

MESSENGER spacecraft images have revealed portions of Mercury never seen by human eyes.

Sun-scorched Mercury is only slightly larger than Earth's Moon. Like the Moon, Mercury has very little atmosphere to stop impacts, and it is covered with craters. Mercury's dayside is super-heated by the sun, but at night temperatures drop hundreds of degrees below freezing. Ice may even exist in craters. Mercury's egg-shaped orbit takes it around the sun every 88 days.

Discovered By		Known by the Ancients
Date of Discovery		Unknown
Orbit Size Around Sun (semi-major axis)		Metric: 57,909,227 km English: 35,983,125 miles Scientific Notation: 5.7909227 x 107 km (0.38709927 A.U.) By Comparison: Earth is 1 A.U. (Astronomical Unit) from the sun.
Perihelion (closest)		Metric: 46,001,009 km English: 28,583,702 miles Scientific Notation: 4.600 x 107 km (3.075 x 10-1 A.U.) By Comparison: 0.313 x Earth
Aphelion (farthest)		Metric: 69,817,445 km English: 43,382,549 miles Scientific Notation: 6.982 x 107 km (0.4667 A.U.) By Comparison: 0.459 x Earth
Sidereal Orbit Period (Length of Year)		0.2408467 Earth years 87.97 Earth days By Comparison: 0.241
Orbit Circumference		Metric: 359,976,856 km English: 223,679,248 miles Scientific Notation: 3.600 x 108 km By Comparison: 0.383 x Earth
Average Orbit Velocity		Metric: 170,503 km/h English: 105,946 mph Scientific Notation: 4.7362 x 104 m/s By Comparison: 1.590 x Earth
Orbit Eccentricity		0.20563593 By Comparison: 12.305 x Earth
Orbit Inclination		7.0 degrees
Equatorial Inclination to Orbit		0 degrees By Comparison: Earth's equatorial inclination to orbit is 23.45 degrees.
Mean Radius		Metric: 2,439.7 km English: 1,516.0 miles Scientific Notation: 2.4397 x 103 km By Comparison: 0.3829 x Earth
Equatorial Circumference		Metric: 15,329.1 km English: 9,525.1 miles Scientific Notation: 1.53291 x 104 km
Volume		Metric: 60,827,208,742 km3 English: 14,593,223,446 mi3 Scientific Notation: 6.08272 x 1010 km3 By Comparison: 0.056 x Earth's
Mass		Metric: 330,104,000,000,000,000,000,000 kg Scientific Notation: 3.3010 x 1023 kg By Comparison: 0.055 x Earth's
Density		Metric: 5.427 g/cm3 By Comparison: 0.984 x Earth
Surface Area		Metric: 74,797,000 km2 English: 28,879,000 square miles Scientific Notation: 7.4797 x 107 km2 By Comparison: 0.147 x Earth
Surface Gravity		Metric: 3.7 m/s2 English: 12.1 ft/s2 By Comparison: If you weigh 100 pounds on Earth, you would weigh 38 pounds on Mercury.
Escape Velocity		Metric: 15,300 km/h English: 9,507 mph Scientific Notation: 4.25 x 103 m/s By Comparison: Escape Velocity of Earth is 25,030 mph
Sidereal Rotation Period (Length of Day)		58.646 Earth days 1407.5 hours By Comparison: 58.81 x Earth
Minimum/Maximum Surface Temperature		Metric: -173/427 °C English: -279/801 °F Scientific Notation: 100/700 K By Comparison: Earth's temperature range is ~ 185/331 K.
Atmospheric Constituents		By Comparison: Earth's atmosphere consists mostly of N2, O2