Solar System Exploration: Planet Selector: Earth & Moon

PLANET SELECTOR

ABOUT EARTH

Earth is an ocean planet. Our home world's abundance of water - and life - makes it unique in our solar system. Other planets, plus a few moons, have ice, atmospheres, seasons and even weather, but only on Earth does the whole complicated mix come together in a way that encourages life - and lots of it.
Read More About Earth >>

Featured Mission: CloudSat
CloudSat creates 3D images of cloud formations to learn more about the dynamics of Earth storms.
Read More About CloudSat >>

VITAL STATISTICS

Average Distance from Sun:	149,597,890 km (92,955,820 miles)
Diameter:	12,756.28 km (7,926.38 miles)
Volume:	1,083,207,000,000 km³ (259,875,000,000 mi³)
Mass:	5,973,700,000,000,000,000,000,000 kg
Length of Day:	23.93 Hours
Length of Year:	365.242 Days
Known Moons:	1

SIZE & DISTANCE

If the Sun was as tall as a typical front door, Earth would be the size of a nickel.

Average Distance from the Sun: 149.597,890 km (1 A.U.)

EXTREME SPACE

A Steady Hand
The Moon is more than a pretty accessory in our night sky. It stabilizes Earth's wobble, which led to a more stable climate and probably helped life evolve. The Moon also guides the ebb and flow of Earth's oceans.

Go West, Young Continent
Earth's land surfaces are constantly in motion. North America is creeping west into the Pacific Ocean at a rate roughly equal to the growth of your fingernails.

Free Moon
Astronauts planted six American flags on the Moon, but that doesn't mean the United States owns it. An international law written in 1967 prevents any single nation from owning planets, stars or any other natural objects in space.

Shields Up
Earth's atmosphere does more than just give us air to breath. It shields us from almost all the harmful radiation of the Sun and protects us from most meteorite impacts. Without our atmosphere, Earth would be a lifeless, cratered hunk of rock such as the Moon or Mercury.

Constant Bombardment
Earth is hit by up to 10,000,000 kg (22,000,000 lbs) of meteors each day - and hardly anyone notices. Most of the material is dust-like grains so light they actually drift gently to Earth.

Flip Side
Humans have studied the Moon for thousands of years, but we didn't see its far side until a spacecraft got there 1959. That's because the Moon rotates once on its axis in about the same time it orbits Earth. That means the same side faces Earth at all times.

TIMELINE

1610 - Galileo Galilei is the first to use a telescope to make scientific observations of the Moon.

1957 - Russia's Sputnik becomes Earth's first artificial satellite. The launch marks the beginning of the Space Age.

1959-1960 - Russia's Luna 1, 2 and 3 probes are the first to fly by, impact and photograph the far side of the Moon.

1969 - Astronaut Neil Armstrong is the first of 12 humans to walk on the surface of the Moon. The last person walked on the Moon in 1972.

1998 - NASA's Lunar Prospector discovers ice at both poles.

2000-now - In 2006, NASA's GRACE satellite discovered a 300-mile-wide crater known as the Wilkes Land impact, found nearly a mile beneath East Antarctica's icy surface.

SLIDE SHOW

First View of Earth from the Moon (1966)
Earth and Moon from 11.6 million km (7.2 million miles)
Earthrise from Lunar Orbit
First U.S. Moon Landing (1966)
Astronaut Visits Surveyor 3 on the Moon
Moon from Earth Orbit
Space Shuttle and Aurora Australis
Eruption of Mt. Etna (2002)
Battered Moon
Earth from 6.4 billion km (4 billion miles)

MOONS

Only Earth itself has received more scientific attention than its only natural satellite. More than 70 spacecraft have been sent to explore the Moon and 12 humans have walked on its surface. The Moon stabilizes Earth's wobble, which has led to more stable climate and possibly aided in the evolution of life. Our Moon may hold many of the answers to Earth's earliest history.