Mercury (2)
Diameter 4,880 km
3,032 mi.
Distance from the Sun 58 million km
36 million mi.
Astronomical Unit 0.39 AU
Mass 0.055 M⊕
Density 5.43 g/cm³
Temperature 430°C
Number of moons 0
Length of day 58 days
Length of year 88 days
Atmosphere Components Molecular oxygen


Mercury is the closest planet to the Sun and it is the smallest planet in the solar system. Mercury has no atmosphere, because of the surface temperatures are about 430°C (806°F).[1]

Mercury is not much bigger than our Moon, it is about four times of the size of Earth.

Messenger of the GodsEdit


A fleet messenger.

Mercury was the Roman messenger god. Mercury is the Roman equivalent of the Greek god Hermes, and was not a signficant part of the Roman religion it was reconciled with the Greek myths.

As the Romans expanded their territory, they began to interperet the mythology of other religions as being identical to their own. The popular gods Lugus, among the Celtic tribes, and Odin (or Wotan) among the Germanic peoples, were both identified as Mercury. Julius Caesar wrote that the German peoples, as well as the Celts of Britain and Gaul, most worship Mercury.

The planet Mercury and the element mercury (Hg) are both named after the Roman god.


Mercury surface

The surface of Mercury.

Mercury landscape

Landscape of Mercury in artwork.

Mercury's surface is overall very similar in appearance to that of the Moon, showing extensive mare-like plains and heavy cratering, indicating that it has been geologically inactive for billions of years.

The surface of Mercury has numerous interesting features, including a variety of craters, ridges, and terrains ranging from heavily cratered to nearly crater free. These features, and their location across the known planet surface, helps us to understand the evolution of the planet. Craters on Mercury are named mainly after artists, while plains have generally been named after mythological and religious figures. Several features are named after famous astonomers and observatories. Several different types of craters can be seen, including young craters in otherwise smooth terrain, new craters on top of old craters, craters with peaks in the center, and craters with lines or "rays" of bright material pointing out from the central crater.

Mariner 10Edit

Mariner 10

This model of Mariner 10 shows the spacecraft as it appeared during flight.

After the Venus flyby, Mariner's trajectory was bent in toward the Sun to accelerate and fling it out of Venus's gravitational field and onward to Mercury. Mariner 10 reached Mercury on March 29, 1974, passing over the planet at 705 kilometers (438 miles) above the surface. A second encounter with Mercury occurred on September 21, 1974, at an altitude of about 47,000 kilometers (29,200 miles). The sunlit side of the planet and the south polar region were photographed. A third and last Mercury encounter, at an altitude of 327 kilometers (203 miles), occurred on March 16, 1975. About 300 additional photographs were obtained along with magnetic field measurements. Photographs of the planet reveal an intensely cratered, Moon-like surface and a faint atmosphere of mostly helium, resulting from solar wind bombardment. Engineering tests were continued until March 24, 1975, when the supply of attitude-control gas was depleted and the mission was terminated.



Artist's impression of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in orbit at Mercury.

MESSENGER launched on 3 August 2004 at 6:15:56 UT (2:15:56 a.m. EDT) on a Delta 7925H (a Delta II Heavy launch vehicle with nine strap-on solid-rocket boosters). The spacecraft was injected into solar orbit 57 minutes later. The solar panels were then deployed and the spacecraft began sending data on its status. The first of three Mercury flybys, all at 200 km altitude, will be on 14 January 2008, the second will be on 6 October 2008, and the third on 29 September 2009. There will also be five deep space manuevers. Data collected during the Mercury flybys will be used to help plan the scientific campaign during the orbital phase. Mercury orbit insertion will take place on 18 March 2011, requiring a delta-V of 0.867 km/s. The nominal orbit is planned to have a periapsis of 200 km at 60 degrees N latitude, an apoapsis of 15,193 km, a period of 12 hours and an inclination of 80 degrees. The periapsis will slowly rise due to solar perturbations to over 400 km at the end of 88 days (one Mercury year) at which point it will be readjusted to a 200 km, 12 hour orbit via a two burn sequence. Data will be collected from orbit for one Earth year, the nominal end of the primary mission will be in March 2012. Global stereo image coverage at 250 m/pixel resolution is expected. The mission should also yield global composition maps, a 3-D model of Mercury's magnetosphere, topographic profiles of the northern hemisphere, gravity field to degree and order 16, altitude profiles of elemental species, and a characterization of the volatiles in permanently shadowed craters at the poles.



This illustration shows the Mercury Composite Spacecraft approaching Mercury, where the two orbiters will separate and be deployed in their dedicated orbits.

While ESA had previously been targeting a launch in July 2014, a 2015 option has always been built in to the development plan, as part of the risk mitigation strategy.

Mercury is a planet of extremes, with its very high density, surface temperature, and strong interaction with the solar wind. Understanding its properties and origin will give scientists important insights into the evolution of the Solar System. BepiColombo involves a carrier spacecraft and two separate orbiters, one developed by ESA and the other by JAXA, dedicated to a comprehensive exploration of Mercury and its environment.

So close to the Sun, the spacecraft will have to endure hostile conditions, in particular temperatures reaching over 450 degrees Celsius. A number of new and critical technologies have had to be developed in order for the mission to reach Mercury and operate there. These include the solar arrays, the electric propulsion system, the antenna assemblies, and the complex thermal management system. The industrial contractors (led by Astrium GmbH in Friedrichshafen, Germany) working with ESA on the mission have recently assessed the current status of the development of these items and have concluded that the first launch window of July 2014 can no longer be met.

Launch opportunities of typically one-month duration for BepiColombo are dictated by positions of the Earth, Venus, and Mercury, allowing the spacecraft to follow its intricate interplanetary trajectory. The next launch opportunity to Mercury occurs in August 2015 and is consistent with the projected completion date of the spacecraft, including margins.

All stakeholders, including the Science Programme Committee and the international partners, have been made aware of the issues affecting the launch date.