Image taken by the NASA probe Messenger on its approach to Mercury.
- Mercury is the planet nearest the sun. It has a diameter of only 3,032 miles (4,879 km), around 40% of Earth's diameter.
- The planet orbits the sun at an average distance of around 36 million miles (58 million km), compared with 93 million miles (150 million kilometers) for Earth.
- Mercury is the smallest planet in the solar system, Jupiter's moon Ganymede and Saturn's moon Titan are also both larger in diameter.
- Mercury orbits the sun faster than any other planet, taking only 88 days to make one complete orbit.
- The planet rotates on its axis extremely slowly, taking 59 days compared to Earth's 24 hours.
- The sun appears around two and a half times larger in its sky compared to how we see the sun on Earth.
- Despite incredibly warm surface temperatures water ice exists in the permanently shadowed parts of craters in Mercury's north polar region.
- NASA's Messenger spacecraft crash landed into Mercury after running out of fuel in April 2015, it surveyed the planet over a four year period gathering new data.
- Mercury is usually very difficult to see in the night sky with the naked eye.
Strange looking crater imaged by Messenger.
Mercury's SurfaceThe planet's colorless and cratered surface gives it a similar appearance to the moon, indeed like the moon it is covered in fine dust particles, between the craters there are smooth plains, mountains and valleys.
Mercury's AtmosphereThe planet has very little atmosphere, only tiny amounts of helium, hydrogen, oxygen and sodium. Because of the lack of atmosphere Mercury's sky is black with stars being visible during the day.
Mercury's TemperatureMercury's lack of atmosphere leaves it unprotected from the sun's rays. The temperature on the planet may reach 450C (840F) during the day but at night the temperature may drop as low as -170C (-275F).
MoonsMercury has no moons.
Life on MercuryIt is improbable that any form of life could exist in the harsh conditions.
Origin of NameThe Romans named the planet after the messenger to the gods.
Is Mercury Just Like the Moon?
The cratered surface of Mercury.
Missions to Mercury
Agency: ESA & JAXA
Summary: Two orbiters built by the ESA (Europe) and JAXA (Japan) which will hopefully gather a large range of data on its 1 year mission around the planet.
MessengerLaunch: August 2004
Arrival: March 2011
Summary: Messenger made three flybys of Mercury before making its orbital insertion in March 2011, the spacecraft undertook a comprehensive four year survey of the planet before crash landing into its north polar region in April 2015.
Mariner 10Launch: November 1973
Arrival: March 1974
Summary:Mariner 10 was the first spacecraft to use "gravity assist", flying close to a planet to increase speed. It made 3 flybys during 1974-75 taking 3,500 images. It is believed to be still flying past the planet every 6 months.
Planet Mercury StatisticsDiameter: 3,032 miles (4,880 km)
Average Distance from Sun: 36 million miles (58 million km)
Orbital Period: 88 days
Rotation Period: 59 days
Maximum Surface Temperatures: 450C (840F)
Minimum Surface Temperatures: -170C (-275F)
Gravity: 3.7 m/s2 (38% Earth's Gravity)
Density: 5.427 g/cm3 (98.4% Earth's Density)
Mass: 3.3022 x 1023 kg (5.5% Earth's Mass)
Volume: 6.08272 x 1010 km3 (5.6% Earth's Volume)
Atmosphere: 42% Molecular oxygen, 29.0% sodium, 22.0% hydrogen, 6.0% helium, 0.5% potassium, Trace amounts of argon, nitrogen, carbon dioxide, water vapor, xenon, krypton and neon.
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