The brightest and largest object in our night sky, the Moon makes Earth a more livable planet by moderating our home planet's wobble on its axis, leading to a relatively stable climate.

It also causes tides, creating a rhythm that has guided humans for thousands of years. The Moon was likely formed after a Mars-sized body collided with Earth.

Earth's Moon is the fifth largest of the 200+ moons orbiting planets in our solar system.
Earth's only natural satellite is simply called "the Moon" because people didn't know other moons existed upon it's discovery.

The Earth and Moon are tidally locked. Their rotations are so in sync we only see one side of the Moon. The Moon has a solid, rocky surface cratered and pitted from impacts by asteroids, meteorites, and comets.

A perfect relaxing trip away to help regain perspective and come back refreshed. While you’re there, take in some history by visiting the Luna 2 and Apollo 11 landing sites.

Jupiter's moon Io is the most volcanically active world in the Solar System, with hundreds of volcanoes, some erupting lava fountains dozens of miles (or kilometers) high. Io is caught in a tug-of-war between Jupiter's massive gravity and the smaller but precisely timed pulls from two neighboring moons that orbit farther from Jupiter, Europa and Ganymede.

Io is only slightly larger than Earth’s moon and about one-quarter the diameter of Earth itself.

Tidal Lock: Over 1.8 Earth days, Io rotates once on its axis and completes one orbit of Jupiter,
causing the same side of Io to always face Jupiter.

Io has no known rings, but it does create a gaseous torus of material along its orbit around Jupiter.

Io almost certainly could not support life as we know it. But that’s not to say it couldn’t
harbor some form of life as we don’t know it.

Europa may be the most promising place in our solar system to find present-day environments
suitable for some form of life beyond Earth.

There is very strong evidence suggesting Europa's ocean is in contact with rock. This is important because life as we know it requires three key basic "ingredients": liquid water, an energy source, and organic compounds to use as the building blocks for biological processes.

Europa could have all three of these ingredients, and its ocean may have existed for the whole age of the solar system, long enough for life to begin and evolve there.

Europa's surface is mostly solid water ice. It is crisscrossed by fractures. Europa's subsurface ocean might contain more than twice as much water as Earth's oceans combined.

Callisto is Jupiter’s second largest moon and the third largest moon in our solar system. Its surface is the most heavily cratered of any object in our solar system. Images of Callisto captured by passing spacecraft show bright white spots standing out against darker regions. The bright areas are mostly ice and the
darker patches are areas where the ice has eroded.

Once thought to be a dead, inactive rocky body, data gathered by the Galileo spacecraft, Callisto may have a salty ocean beneath its icy surface. More recent research reveals that this ocean may be located deeper beneath the surface than previously thought, or may not exist at all. If an ocean is present, it’s possible the ocean is interacting with rock on Callisto, creating a potential habitat for life.

A day on Callisto is about 17 Earth days, the same amount of time it takes Callisto to orbit Jupiter once.

Saturn’s largest moon Titan is an extraordinary and exceptional world. Among our solar system’s more than 150 known moons, Titan is the only one with a substantial atmosphere. And of all the places in the solar system, Titan is the only place besides Earth known to have
liquids in the form of rivers, lakes and seas on its surface.

Saturn’s largest moon Titan is the second largest moon in the solar system. It is bigger than planet Mercury. The same side of Titan always faces Saturn, so Titan takes 16 days to orbit Saturn and to rotate once.

Titan is an icy moon with a surface of rock-hard water ice, but Titan also likely has a liquid water ocean beneath its surface. Titan is the only moon in the solar system known to have a substantial
atmosphere, which is mostly nitrogen like Earth’s.

Titan’s air is dense enough that you could walk around without a spacesuit. But you’d need
an oxygen mask and protection from the bitter cold.

The name Iapetus comes from the Greek god (or Titan) Iapetus, who is a son of Uranus and Gaia, a brother to Kronus and the father of Atlas and Prometheus. As the father of Prometheus, the ancient
Greeks regarded Iapetus as the father of the human race.

Despite the great distance, Saturn has tidally locked Iapetus. The moon always presents the same face toward Saturn. With its distant, inclined orbit, Iapetus is the only large
moon from which there is a nice view of the rings of Saturn.

The second most notable feature of Iapetus is its "equatorial ridge," a chain of 6-mile (10-km) high mountains girdling the moon's equator. The ridge appears to break up and distinct, partially bright mountains are observed. The Voyager I and Voyager II encounters provided the first knowledge of these mountains, and they are informally referred to as the Voyager Mountains.