Where did we come from? Are we alone in the Universe? We can only answer these questions by exploring the planets and other worlds of our Solar System and beyond. Learn why these worlds are so important, and how you can get involved.

The Sun, our Solar System’s star

We study the Sun to learn about how stars work, and to help protect our civilization from solar storms.

Mercury, world of extremes

Mercury a little-explored world, full of mystery, with a surface split into extremes and an interior that puzzles scientists.

Venus, Earth's twin sister

Venus hosts brutal conditions today, but the planet may have once been more hospitable to life.

Earth, our home planet

Earth, the only planet known to support life, offers liquid water, an oxygen-rich atmosphere, and protection from the Sun’s harmful radiation.

The Moon, gateway for science and exploration

The Moon is the only world besides Earth ever walked on by humans. By studying it, scientists can learn about Earth’s past and better understand worlds throughout the galaxy.

Global view of Mars from MOM: Tharsis Montes and Valles Marineris

Mars, the red planet

Mars once had liquid water on the surface and could have supported life. Scientists are uncovering how it transformed into the cold, dry desert-world it is today.

Asteroids, comets, and other small worlds

Asteroids and comets are windows into the Solar System's past and a potential threat to Earth today.

Jupiter, the planet with a planetary system of its own

Jupiter, our largest planet, teaches us how planetary systems evolve. Its four planet-like moons make it a planetary system of its own.

Io, Jupiter’s chaotic volcano moon

Io, one of Jupiter's four Galilean moons, is known for its explosivity.

Europa, Jupiter’s possible watery moon

Europa is the sixth-largest moon in the solar system and Jupiter’s fourth-largest satellite.

Saturn, planet of rings, moons and more to explore

Saturn is the crown jewel of our solar system. It has a stunning set of rings, diverse moons, and so much more to explore.

Enceladus, Saturn’s moon with a hidden ocean

With its subsurface ocean and so-called "tiger stripes," Enceladus is one of Saturn's most fascinating moons.

Titan, a moon with familiar vistas

Saturn's largest moon, Titan, is both the only other place in the Solar System with liquid on its surface and the only moon with a thick atmosphere, making it a tantalizing destination to search for life.

Uranus, the sideways planet

Uranus may be the butt of all planet jokes, but there's much more to this world than potty humor.

Neptune, planet of wind and ice

Neptune, our outermost planet, is a windy blue world with exotic ice, raging storms, rings, and a moon that could have a subsurface ocean.

Triton, Neptune's largest moon

Triton is likely a captured Kuiper Belt Object and possibly an ocean world.

High-resolution enhanced-color global MVIC portrait of Pluto

Pluto, the Kuiper Belt’s most famous dwarf planet

Pluto is a dwarf planet and the largest of the Kuiper Belt objects (KBOs) — a collection of ice-rock bodies found outside Neptune’s orbit.

Exoplanets, worlds beyond the Solar System

Some exoplanets could be habitable and are prime targets in the search for life beyond Earth.

A Pale Blue Dot

Look again at that dot. That's here. That's home. That's us.

What is a Planet?

It's right there in our name: The Planetary Society. But what is a planet? This seemingly simple question is the subject of much debate.

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All Rosetta NAC images of Steins (animation)

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Last week in Science magazine appeared the first peer-reviewed article on the results of Rosetta's September 2008 encounter with the smallish main-belt asteroid Steins. This morning I got a chance to sit down and read the article, and I wrote up a summary.

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