Earth's Moon 2

Unlike Earth, the Moon does not have moving crustal plates or active volcanoes. However, seismometers planted by the Apollo astronauts in the 1970s have recorded small quakes at depths of several hundred kilometers. The quakes are probably triggered by tides resulting from Earth's gravitational pull. Small eruptions of gas from some craters, such as Aristarchus, have also been reported. Local magnetic areas have been detected around craters, but the Moon does not have a magnetic field resembling Earth's.

A surprising discovery from the tracking of the Lunar Orbiter spacecraft in the 1960s revealed strong areas of high gravitational acceleration located over the circular maria. These mass concentrations (mas-cons) may be caused by layers of denser, basaltic lavas that fill the mare basins.

In 1998, the Lunar Prospector spacecraft team reported finding water ice at both poles. Comet impacts deposited water on the Moon. Some of it migrated to very dark, very cold areas at the poles.

Much remains to be learned about our Moon. Researchers continue to study the samples and data returned by Apollo and other missions, as well as lunar meteorites.

Earth's Moon: Facts & Figures

Discovered By: Known by the Ancients

Date of Discovery: Unknown

Average Distance from Earth

Metric: 384,400 km
English: 238,855 miles
Scientific Notation: 3.84400 x 105 km (0.00257 A.U.)
By Comparison: 0.00257 x Earth's Distance from the Sun

Perigee (closest)

Metric: 363,300 km
English: 225,700 miles
Scientific Notation: 3.633 x 105 km (0.00271 A.U.)
By Comparison: 0.00247 x Earth's Distance from the Sun

Apogee (farthest)

Metric: 405,500 km
English: 252,000 miles
Scientific Notation: 4.055 x 105 km (0.00243 A.U.)
By Comparison: 0.00267 x Earth's Distance from the Sun

Equatorial Radius

Metric: 1737.4 km
English: 1079.6 miles
Scientific Notation: 1.734 x 103 km
By Comparison: 0.2724 x Earth

Equatorial Circumference

Metric: 10,916 km
English: 6,783 miles
Scientific Notation: 1.0916 x 104 km

Volume

Metric: 21,970,000 km3
Scientific Notation: 2.197 x 1010 km3
By Comparison: 0.020 x Earth

Mass

Metric: 73,483,000,000,000,000,000,000 kg
Scientific Notation: 7.3483 x 1022 kg
By Comparison: 0.0123 x Earth

Density

Metric: 3.341 g/cm3
By Comparison: 0.606 x Earth

Surface Area

Metric: 37,932,330 km2
English: 14,645,750 square miles
Scientific Notation: 3.793233 x 107 km2
By Comparison: 0.074 x Earth

Equatorial Surface Gravity

Metric: 1.622 m/s2
English: 5.322 ft/s2
By Comparison: 0.166 x Earth

Escape Velocity

Metric: 8,568 km/h
English: 5,324 mph
Scientific Notation: 2,380 m/s
By Comparison: 0.213 x Earth

Sidereal Rotation Period (Length of Day)

27.321661 Earth days
655.72 hours
By Comparison: Synchronous With Earth

Sidereal Orbit Period (Length of Year)

0.075 Earth years
27.321661 Earth days
By Comparison: Orbit Period = Rotation Period

Mean Orbit Velocity

Metric: 3,682.8 km/h
English: 2,288.4 mph
Scientific Notation: 1,023 m/s
By Comparison: 0.034 x Earth

Orbital Eccentricity

0.05490
By Comparison: 3.285 x Earth


Orbital Inclination to Ecliptic

5.145 degrees
By Comparison: Oscillates roughly 0.15 degrees in 173 days.

Equatorial Inclination to Orbit

6.68 degrees

Orbital Circumference

Metric: 2,290,000 km
English: 1,423,000 miles
Scientific Notation: 2.290 x 106 km

Minimum/Maximum Surface Temperature

Metric: -233/123 °C
English: -387/253 °F
Scientific Notation: 40/396 K

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