Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS

NOVA Online: Hunt for Alien Worlds (see bottom of page for navigation)
Worlds sidebar (see bottom of page for navigation)

The EarthYes! You've found the Earth, a habitable planet! The Earth is the solar system's fifth largest planet in diameter and its most dense. The Earth is the only planet in the solar system that has oxygen in the atmosphere and liquid water, which covers almost three-quarters of the planet's surface. The Earth's oceans also help maintain the planet's moderate temperatures.

There was probably much more carbon dioxide in the Earth's atmosphere when the Earth was first formed and when the first basic cellular life started.



Photo courtesy NASA





Worlds Home | Alone? | Stargazer
Constellations | Star Map | Planets
Life | Resources | Table of Contents


Support provided by

For new content
visit the redesigned
NOVA site


NOVA Home | WGBH Home | PBS Home
Search | Feedback | Shop | Printable Page
© 1997 WGBH