The Inner Planets: Mercury, Venus, and Mars

The Inner Planets: Mercury, Venus, and Mars — page 5
CHARACTERISTICS OF MERCURY he planet that orbits closest to the Sun is Mercury It is also the smallest of the eight planets in the solar system These features make Mercury difficult to view from Earth as the small planet rises and sets within about two hours of the Sun Observers on Earth can only ever see the planet during twi light when the Sun is just below the horizon Relatively little was known about Mercury until the Mariner 10 spacecraft visited it in 1974 75 It was more than 30 years before another spacecraft Messenger visited the planet Mercury's orbit lies between the Sun and the orbit of Venus Along with Venus Earth and Mars Mercury is one of the inner planets nearest to the Sun The inner planets are also known as the terrestrial or Earth like plan ets They are dense rocky bodies that are much smaller than the solar system s outer planets Mercury has no known moons SIZE Mass AND DENSITY Mercury is the smallest planet in both mass and diameter It is about 18 times less massive IO