The Swiftest Planet



    The Latest

    Oct. 20, 2018: The latest mission to Mercury is on its way. The ESA-JAXA BepiColombo mission to Mercury blasted off on an Ariane 5 rocket from Europe's Spaceport in Kourou, French Guiana, on an international mission to study our solar system's innermost planet.

    Mercury has only been visited by two spacecraft—NASA's Mariner 10 and MESSENGER. BepiColombo's two spacecraft will double that number. The mission includes two science orbiters: ESA's Mercury Planetary Orbiter and Japan's Mercury Magnetosphere Orbiter.

    BepiColombo will enter Mercury orbit in 2025 after a complex series of planetary flybys, including one Earth flyby, two Venus flybys and six Mercury flybys.

    Explore Mercury In Depth ›

    Ten Things to Know About Mercury

    10 Things to Know About Mercury



    Mercury is the smallest planet in our solar system—only slightly larger than Earth's Moon. 



    It is the closest planet to the Sun at a distance of about 36 million miles (58 million kilometers) or 0.39 AU.


    Long Days, Short Years

    One day on Mercury (the time it takes for Mercury to rotate or spin once with respect to the stars) takes 59 Earth days. One day-night cycle on Mercury takes 175.97 Earth days. Mercury makes a complete orbit around the Sun (a year in Mercury time) in just 88 Earth days.

    Mercury Transit - November 2006


    Rough Surface

    Mercury is a rocky planet, also known as a terrestrial planet. Mercury has a solid, cratered surface, much like the Earth's moon.


    Can't Breathe It

    Mercury's thin atmosphere, or exosphere, is composed mostly of oxygen (O2), sodium (Na), hydrogen (H2), helium (He), and potassium (K). Atoms that are blasted off the surface by the solar wind and micrometeoroid impacts create Mercury's exosphere.



    Mercury has no moons. 



    There are no rings around Mercury. 


    Tough Place to Live

    No evidence for life has been found on Mercury. Daytime Temperatures can reach 430 degrees Celsius (800 degrees Fahrenheit) and drop to -180 degrees Celsius (-290 degrees Fahrenheit) at night. It is unlikely life (as we know it) could survive on this planet.


    Big Sun

    Standing on Mercury's surface at its closest approach to the Sun, our star would appear more than three times larger than it does on Earth.


    Robotic Visitors

    The two spacecraft of ESA-JAXA's BepiColombo are en route to Mercury. NASA's Mariner 10 was the first mission to explore Mercury. NASA's MESSENGER was the first to orbit the innnermost planet.

    Hollows on Mercury

    Did You Know?

    Did You Know?

    Because of Mercury's elliptical—egg-shaped—orbit and sluggish rotation, the morning Sun appears to rise briefly, set and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset.

    Pop Culture

    Pop Culture

    The smallest planet in our solar system has a big presence in our collective imagination. Scores of science fiction writers have been inspired by Mercury, including Isaac Asimov, C. S. Lewis, Ray Bradbury, Arthur C. Clarke and H. P. Lovecraft. Television and film writers, too, have found the planet an ideal location for storytelling. In the animated television show Invader Zim, Mercury is turned into a prototype giant spaceship by the extinct Martians. And in the 2007 film Sunshine, the Icarus II spacecraft goes into orbit around Mercury to rendezvous with the Icarus I.

    In the comic strip Calvin and Hobbes, Calvin and his classmate Susie give a presentation about Mercury, in which Calvin's contribution is full of questionable information: "The planet Mercury was named after a Roman god with winged feet," says Calvin. "Mercury was the god of flowers and bouquets, which is why today he is a registered trademark of FTD florists. Why they named a planet after this guy, I can't imagine."

    Kid-Friendly Mercury

    Illustration of Mercury

    Kid-Friendly Mercury

    Mercury is the smallest planet in our solar system. It’s a little bigger than Earth’s Moon. It is the closest planet to the Sun, but it’s actually not the hottest. Venus is hotter.

    Along with Venus, Earth, and Mars, Mercury is one of the rocky planets. It has a solid surface that is covered with craters like our Moon. It has a thin atmosphere, and it doesn’t have any moons. Mercury likes to keep things simple.

    Mercury spins slowly compared to Earth, so one day lasts a long time. Mercury takes 59 Earth days to make one full rotation. But a year on Mercury goes fast. Because it’s the closest planet to the sun, it goes around the Sun in just 88 Earth days.

    Visit NASA Space Place for more kid-friendly facts.

    NASA Space Place: All About Mercury ›



    Planetary Photojournal: Mercury

    Johns Hopkins University MESSENGER Mission Site

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