Explore Worlds
Find Life
Defend Earth
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.
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 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.
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.
Learn MoreLatest Articles
Historical PDF: "The Voyager Flights to Jupiter and Saturn"
A while ago I posted all 99 issues of the Voyager Mission Status Bulletins in PDF format, and now I have another cool item to add to that collection: NASA EP-191,
Nearly behind Saturn
Some recent photos that Cassini took from a position nearly in Saturn's shadow caught my eye, and I made a quick color composite. What an amazing view this would be if you were riding on the spacecraft!
Mercury's Weird Terrain
When Mariner 10 flew past Mercury, it caught an immense impact basin lying half in and half out of sunlight, which they named Caloris. Even with only half the basin visible, scientists knew it was one of the largest in the solar system. Geologists had to wait more than 25 years to see the rest of Caloris, and when they did it turned out to be even bigger than they had thought. But the fact that Caloris was only half in sunlight was fortuitous in one sense, because it meant that the spot on Mercury that was exactly opposite the area of the Caloris impact was also partially in sunlight. That spot looks weird.
Lovely crater turns up in MoonZoo; 2 million images classified, lots more Moon left
Here's a very pretty picture to start off the week: a really gorgeous fresh crater on the lunar farside. There's nothing particularly unusual about this crater; it's just recent and fresh so there's a mesmerizing amount of detail in the feathery patterns of the ejecta that fans outward from it.