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  • Jupiter is the largest planet in the solar system. It can hold the equivalent of over 1,000 Earths. However, because Jupiter is made mostly of gases, it's 'surface' gravity is only 2.4 times that of Earth's.

  • Jupiter has a thin ring system that's largely obscured because it's made of dust rather than ice.

  • jupiter rings
    A glimpse of Jupiter's faint ring system as seen by New Horizons on its way to Pluto.

  • Jupiter's magnetic field is the strongest in the solar system. It's thought to be caused by convection within the planet's liquid metallic core. The field is so strong radthat amateur radio operators on Earth have no problem picking up the planet's electromagnetic interference which, at times, exceeds that of the sun.

  • Eerie sounds of Jupiter picked up by the Cassini probe while en route to Saturn.

  • Jupiter's most famous feature is the Great Red Spot, a massive storm that has raged for centuries with speeds up to 270 miles per hour. The spot has been steadily shrinking.

  • grs
    The Voyager 1 probe's iconic shot of the Great Red Spot in 1979.

  • Jupiter's is 90% hydrogen, 10% helium and a negligible amount of other compounds such as ammonia and methane.

  • Moons

    Jupiter's 4 largest moons, also called the Galilean moons, are Io, Ganymede, Callisto and Europa.

    From left to right: Io, Europa, Ganymede, Callisto,

    With over 400 active volcanoes, Io is the most volcanically active body in the solar system, a phenomenon caused largely by Jupiter's immense gravity pulling on the moon. Shown here is the volcano Tvashtar erupting and ejecting material over 200 miles above the surface.

  • Europa has attracted a lot of attention from scientists because of its theorized subsurface salty ocean. Estimates indicate that Europa may have twice as much water as Earth. A recent study points out that the theoretical hydrogen-oxygen ratio Europa could produce is roughly the same as on Earth, lending credence to the existence of life on this icy moon. NASA plans to send a probe to Europa in the early 2020's.

  • europa
    Shown here is a false color image of Europa's ice layer taken by the Galileo probe.

  • Were it orbiting the sun, Ganymede would be classified as a planet. It has the largest mass of any planetary satellite.

  • Ganymede is the only moon known to have a magnetic field, likely created through convection inside its liquid iron core.

  • Like Europa, Ganymede is thought to have a subsurface ocean althought scientists are skeptical it contains life.

  • ganymede
    Ganymede's surface, seen in the left-hand picture, compared to Europa's surface.

  • Callisto is one of the most cratered and oldest objects in the solar system. None of its surface features appear to have been caused by tectonic activity.

  • Callisto may also hold liquid water beneath its surface.

  • Callisto orbits over a million miles away from Jupiter. For comparison, our moon orbits around 240,000 miles away from Earth.

  • Callisto's low levels of radiation means it may be suitable for future human colonization.

  • callisto callisto surface
    The Valhalla crater, shown on the left, is one of the most distinctive feature on Callisto's surface. On the right is a close up of Callisto's Asgard Basin region.

By Aaron Feigenbaum