Planet Mercury
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Planet Mercury
planet mercury Image taken by Messenger on its approach to Mercury

"Spider" Impact crater
Spider Impact crater Strange looking crater imaged by Messenger
Planet Mercury Facts
  • Mercury is the planet nearest the sun. It has a diameter of 3,032 miles (4,879 km), about two-fifths of Earth's diameter.
  • The planet orbits the sun at an average distance of about 36 million miles (58 million km), compared with about 93 million miles (150 million kilometers) for Earth.
  • It is dry, extremely hot, and almost airless.
  • The sun's rays are approximately seven times as strong on Mercury as they are on the Earth.
  • The sun also appears about 2 1/2 times larger in the sky compared to how we see the sun on Earth.
  • Scans of the planet made by Earth-based radar indicate that craters at its poles contain water ice.
  • It travels round the sun faster than any other planet, taking only 88 days to make a full orbit of the sun.
  • The planet rotates on its axis extremely slowly, taking 59 days compared to Earth's 24 hours.
  • The planet is often very difficult to see in the night sky with the naked eye.
Mercury's Surface
Its surface appears to be much like that of the moon. It is covered by a thin layer of minerals called silicates in the form of tiny particles. It has many deep craters and flat plains but unlike the moon it has steep cliffs.

Mercury's Atmosphere
The 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 Temperature
Mercury doesn't have enough atmosphere to protect it 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).
Moons, Name and Life
surface of mercury
The cratered surface of Mercury.

Moons & Origin of Name
Mercury has no moons.
The Romans named the planet after the messenger to the gods.

Life on Mercury
It is improbable that any form of life could exist in the harsh conditions.


Is Mercury Just Like the Moon?
Planet Mercury
The Moon
Superficially Mercury seems very like the Moon, a long dead world with no atmosphere to speak of featuring extremely high temperatures during the day and freezing cold temperatures at night. The terrain also looks very similar, a highly cratered surface made up of a powdery grey dust. So what are the differences if any?

The first major difference is when you compare the density of the two worlds. Mercury’s density is much higher than the Moon’s and actually almost equal to Earth’s. This means that a portion of the planet would weigh only slightly less than an equal portion of Earth. This is because Mercury has a large iron core which accounts for 40% of its volume. Which brings us to the second major difference, it has an active molten iron core which means that like Earth and unlike the Moon it produces its own magnetic field, although the strength of the field is only around 1% of Earth’s. The third difference is that the force of gravity found on Mercury is more than twice as strong as that found on the Moon, the planet’s gravity is around two fifths of that we have on Earth. Lastly it has recently been discovered that the planet was far more volcanically active in its early history than previously thought, much more so than the Moon. Indeed the latest evidence indicates that there may have been geological activity up until 1 billion years ago, if this evidence is confirmed it would mean the planet would have much younger surface features than there are on the Moon.

Mercury is one of the most mysterious planets in our solar system and we are only just learning more about it thanks to a few recent flybys by the NASA spacecraft Messenger. Once the craft is placed in orbit in 2011 new secrets will be revealed about the smallest planet in our solar system.
Images and Video
Crater impact
crater impact
Messenger images of Mercury
Mercury passing the sun
Mercury passing sun
Future and Past Missions to Mercury
Bepicolombo
bepicolombo Launch: August 2013
Arrival: 2019
Agency: ESA & JAXA
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.


Messenger
messenger Launch: August 2004
Arrival: March 2011
Agency: NASA
Messenger has already made 3 flybys of Mercury before it will make its orbit insertion in 2011, making a comprehensive survey of the planet.

Update: Messenger successfully entered orbit around Mercury 17th March 2011.

Mariner 10
mariner 10 Launch: November 1973
Arrival: March 1974
Agency: NASA
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 Statistics
Comparison with Earth
Diameter: 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.
Diameter: 7,926 miles (12,756 km)
Average Distance from Sun: 93 million miles (150 million km)
Orbital Period: 365.24 days
Rotation Period: 23.934 hours

Maximum Surface Temperatures: 58C (136F)
Minimum Surface Temperatures: -88C (-126F)

Gravity: 9.766 m/s2
Density: 5.515 g/cm3
Mass: 5.9737 x 1024 kg
Volume: 1.0832 x 1012 km3

Atmosphere: 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide, water vapor makes up around 0.4% of Earth's atmosphere depending on climatic conditions.