How did life get started on Earth? Where did it come from? Looking out at other planets may give clues to what might have happened once-upon-a-time on Earth.

When Solar System scientists got together to discuss how Jupiter's mammoth atmospheric storms, Martian soils and evidence of lakes on Venus relate to the search for life's origins, they decided they have only glimpsed what may be Out There. They wanted to do more.

Ancient inner planets. Scientists have discovered that Mars, Earth's nearest planet neighbor, once had more atmosphere. Martian soils show that lakes and deep rivers once covered the Red Planet. Evidence of lakes on Venus suggests that in ancient times the Solar System's inner planets had an abundant water supply -- probably a necessary condition for life.

Large storms seen on Jupiter suggest a natural laboratory for chemical evolution. Scientists also have found oceans of something on Jupiter's satellite Europa.

Such discoveries help trace the origins of Earth, the Solar System and life itself. Interplanetary probes visiting the Sun, Venus Mars, Jupiter, Saturn and its moon Titan may help explain the origin of life.

• Earth is the fifth largest planet in the Solar System and the third planet from the Sun.
• Earth's atmosphere is made of 77 percent nitrogen and 21 percent oxygen, with traces of argon, carbon dioxide, and water.
• Earth is the only planet that has liquid water on its surface. Liquid water covers 71 percent of Earth's surface. The other 29 percent is rock and soil.
• White clouds of water vapor hide much of Earth's surface.
• Earth has one moon.
• Earth is 92,960,000 miles from the Sun.
• The diameter of Earth is 7,926 miles.

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Solar System:	The Sun
Inner System:	Mercury	Venus	Earth	Mars
Outer System:	Jupiter	Saturn	Uranus	Neptune	Pluto
Other Bodies:	Moons	Rings	Asteroids	Comets

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