Solar System

As part of NASA’s real-time science encyclopedia of deep space exploration, you can take a look around the most volcanic object in our solar system: Io, one of Jupiter's moons discovered by the great Renaissance astronomer Galileo Galilei. The moon—roughly the size of Earth's moon—is covered in dozens of active volcanoes, with many erupting lava flows miles into the sky. Io's extreme volcanism results partly from the gravitational tensions from Jupiter and two other nearby moons. Learn more about this lava-filled hot spot in the solar system here.

As stable as Earth feels, our planet is always moving: it's rotating on an axis, revolving around the Sun at the center of its orbit, and through space within the solar system and broader Milky Way galaxy. All these movements occur in a mostly regular way and provide reference points for our record of time: days (rotation), months (lunar cycle), and years (revolution around the Sun). But these patterns aren't quite exact, with the length of a day just a little over 24 hours. This quirk has resulted in some surprising calendar bloopers over the centuries, including September 1752, in the United Kingdom, where 11 days were removed.

The "jewel" of our solar system didn't always have its striking rings. Millions of years ago, a likely icy moon orbited Saturn just a little too closely, reaching the planet's so-called Roche limit, the boundary where the planet's gravity pulls a satellite apart. An estimated 17,000 trillion tons of ice likely exploded into Saturn's orbit over just a few days, suddenly creating what today is clearly seen as the planet's stunning rings. Watch this dramatic animated visualization showing how the process might have looked millions of years ago.

Mercury, the closest planet to our solar system's sun, has an orbit of roughly 88 Earth days, and is not the hottest planet in the solar system (that title goes to Venus and its dense atmosphere). From Mercury's surface, the light of the sun appears 11 times brighter than from Earth, and the Sun itself would appear three times as large. Since Pluto's demotion to dwarf planet, Mercury now claims the smallest planet moniker, coming in only slightly larger than Earth's moon. Explore NASA's official page on Mercury here.

On a dry lakebed in Nevada, a group of friends build the first scale model of the solar system with complete planetary orbits: a true illustration of our planet's humble position in space.

Visualize just how exactly seasons come to be with this animation of the earth in relation to the sun, and see how earth's tilt determines our seasons.