Mercury, Closest to the Sun

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury, the closest planet to the sun, has been studied by multiple spacecraft throughout the years. Scientists have uncovered some amazing findings about the small planet and have even mapped its entire surface. Here are 10 amazing facts about Mercury.



FIRST STOP: Extreme Temperature Swings

Most Extreme Temperature Fluctuations in the Solar System

NASA Goddard Space Flight Center

Even though Mercury is the closest planet to the sun, its surface can still be extremely cold. The temperature during the day can reach 840 degrees Fahrenheit (450 degrees Celsius), but at night, temperatures can get as low as minus 275 F (minus 170 C). That fluctuation equals a temperature swing of more than 1,100 F (600 C), the largest of any planet in the solar system.



NEXT: The Smallest Planet

The Smallest Planet

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury is the smallest planet in the solar system. The diminutive planet is about 3,030 miles (4,876 kilometers) in diameter, making it about the size of the continental United States and only slightly bigger than Earth's moon. It's smaller than both Saturn's moon Titan and Jupiter's moon Ganymede. Pluto used to be considered the smallest planet in the solar system, but it was downgraded to a "dwarf planet," leaving the distinction to Mercury.



NEXT: It's a Survivor

Survived Impact with Giant Asteroid

NASA

Scientists think that a huge asteroid slammed into Mercury about 4 billion years ago, creating a giant crater about 960 miles (1,545 km) across. Called the Caloris Basin, the crater could fit the whole state of Texas inside it. Researchers have calculated that the asteroid that created the basin had to have been about 60 miles (100 km) wide.



NEXT: Mercury's Crazy Orbit

Mercury's Crazy Orbit

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury zips around the sun faster than any other planet. It travels about 112,000 mph (180,000 km/h) along its elliptical orbit. The planet gets as close as 29 million miles (47 million km) to the sun, and as distant as 43 million miles (70 million km) from the sun. The planet takes only 88 Earth days to completely orbit the sun.



NEXT: We've Seen It All

Mercury Has Ice

NASA/JPL/Northwestern University

Scientists think that there is ice inside Mercury's craters. The planet's north and south poles are cold and shadowy, which could allow them to retain water ice. Meteorites and comets could have delivered ice to those areas, or water vapor from Mercury's innards could have seeped out and frozen.



NEXT: There's an Atmosphere, Too!

It Has a Huge, Iron Core

NASA

Mercury's iron core takes up about 75 percent of the planet's radius. The huge core has more iron in it than any other planet's in the solar system. Scientists aren't exactly sure how Mercury's giant iron core formed, but researchers think it has something to do with its formation. If the planet formed quickly, it could have left a thin shell of crust over the relatively large core.



NEXT: Mercury Actually Has Ice

A NASA Probe Mapped Mercury's Entire Surface

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

NASA's MESSENGER probe (short for MErcury Surface, Space ENvironment, GEochemistry, and Ranging mission), which has been orbiting Mercury since 2011, has beamed back some amazing images of the closest planet to the sun. Scientists have used those images to create the first-ever complete map of Mercury's surface.



NEXT: Mercury's Iron Core Is Huge

It Has a Thin Atmosphere

NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Mercury has the thinnest atmosphere of any planet in the solar system. The planet's atmosphere is so thin that scientists have another name for it: an exosphere. The moon and other bodies in the solar system also have exospheres, possibly making it the most common kind of atmosphere in the solar system, NASA scientists have said.



NEXT: Mercury Has Tails

It Has 'Tails'

NASA/JHUAPL/CIW

Scientists have discovered that Mercury has streams of particles sloughing off its surface. Researchers aren't exactly sure what is responsible for the shapes of the tails, but they think it might have something to do with the planet's magnetosphere and the sun's wind.



NEXT: Mercury May Have Had Volcanoes

Mercury May Have Had Volcanoes