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  • Mercury is the closest planet to the sun.

  • A year on Mercury is only 88 Earth days.

  • Mercury has an orbital speed of nearly 112,000 mph, making it the fastest planet in the solar system.

  • The surface can reach a scorching 840 degrees Fahrenheit but since there's no atmosphere to trap the heat, temperatures on the part of Mercury facing away from the sun plummet to as low as -275.

  • Mercury is incredibly dense, with a metallic core spanning roughly 75% of the planet's diameter.

  • Defying scientists' predictions, the Mariner 10 probe discovered that Mercury has a magnetic field, albeit very weak. With its slow rotation and tiny size, Mercury was not expected to have a molten core capable of creating a magnetic field. However, current research suggests that the core could be made of lighter elements like sulfur, which would lower the core's melting temperature.

  • Mercury doesn't have an atmosphere per se but rather, like our Moon, a negligible exosphere made of elements such as oxygen, sodium and hydrogen. Solar winds cause these gases to constantly be blown away and then replenished.

  • The surface of Mercury is estimated to have over 10 times as much sulfur as Earth and Mars.

  • mariner
    Launched in 1973, Mariner 10 was the first probe to visit Mercury as well as the first to send back images of Venus. It mapped almost half of Mercury's surface, discovered the planet's exosphere and magnetic field. The probe stopped transmitting in 1975 and is thought to still be orbiting the sun.
    In 2011, the MESSENGER probe became the first probe to orbit Mercury. Among the many important discoveries it made was water ice, as shown by the yellow spots in this picture.
    The last image of Mercury's surface taken by NASA's Messenger probe. Last year, the probe crashed into an area of Mercury called Shakespeare Basin at over 8,000 mph. This image shows a 58-mile diameter crater called Jokai.
    Next up for Mercury exploration is the ESA's BepiColombo mission, scheduled to launch in 2024. The probe will hopefully shed light on important issues such as the origin of the planet's magnetic field and the disappearance and regeneration of the exosphere. The will consist of two probes, one designed to the study the planet itself and the other to study Mercury's magnetosphere. Shown here is the Planetary Orbiter.

By Aaron Feigenbaum