Planetary Database/Terran/Mercury

The Planetary Database - Terran System - Mercury

Planet Mercury

Mercury is a Class Y and first planet in the Terran Solar System and is named after the Roman god Mercury, envoy of the gods according to Terran mythology.

Having only a minimal atmosphere and orbiting the Terran Star at a distance of just 0.39 Astronomical units. Physically, Mercury is similar in appearance to the Moon as it is heavily cratered. It has no natural satellites and no atmosphere. The planet has a large iron core which generates a magnetic field about 1% as strong as that of the Earth. Surface temperatures on Mercury range from about 90-700 K, with the subsolar point being the hottest and the bottoms of craters near the poles being the coldest.

Magnetosphere

Despite its slow rotation, Mercury has a relatively strong magnetosphere, with 1% of the magnetic field strength generated by Earth. It is possible that this magnetic field is generated in a manner similar to Earth's, by a dynamo of circulating liquid core material. However, scientists are unsure whether Mercury's core could still be liquid,[5] although it could perhaps be kept liquid by tidal effects during periods of high orbital eccentricity. It is also possible that Mercury's magnetic field is a remnant of an earlier dynamo effect that has now ceased, with the magnetic field becoming "frozen" in solidified magnetic materials.

Exploration

Reaching Mercury from Earth poses significant technical challenges since the planet orbits three times closer to the Sun than the Earth. A Mercury-bound spacecraft launched from Earth must travel over 91 million kilometers into the Sun's gravitational potential well. From a stationary start, a spacecraft would require no delta-v or energy to fall towards the Sun. However, starting from the Earth with an orbital speed of 30 km/s, the spacecraft's significant angular momentum resists sunward motion. Hence, the spacecraft must change its velocity considerably to enter into a Hohmann transfer orbit that passes near Mercury.