Planet Mercury
Mercury is the smallest and innermost planet in the solar system. It orbits the Sun once every 88 days. When viewed from our planet; Earth and is bright and range between?2.0 to 5.5 in what is known as apparent magnitude. However, it is not as easily spotted due to the fact that its greatest angular separation from the Sun being only 28.3°. Mercury can only be seen in evening or morning twilight.
Little or not much is known about this planet. The first spacecraft to actually visit the planet was Mariner 10 which succeeded in mapping approximately 45% of it. The second was the recent flyby of the MESSENGER spacecraft which succeeded in mapping 30% of the planet on 14th January 2008. MESSENGER has plans for another fly by to Mercury in 2009 which is followed by an orbital insertion in 2011 before further plans to survey and complete the mapping process of the entire planet.
Mercury and the Moon is similar in appearance. Both of them have no natural satellites, heavily cratered and contains no substantial atmosphere. One difference is that Mercury
has a large iron core that is able to generate a strong magnetic field. The size of the core causes the planet to be exceptionally dense. The surface temperatures range from ?183 °C to 427 °C with the bottoms of the craters close to the poles coldest and the subsolar point the hottest.
One of the four terrestrial planets in the solar system, Mercury was given its English name by the Romans who named it after the Roman god Mercury. The smallest planet on the solar system with a equatorial radius of 2439.7 km also resembles Earth in the sense that it contains a rocky body. The planet is also the 2nd highest in the Solar system in terms of density with 5.427 g/cm³.
The planet consists of about 70% metallic material and 30% in silicate material. The planet is also the 2nd highest in the Solar system in terms of density with 5.427 g/cm³. Based on its density, valuable data about its structure can be inferred. Earth, the most dense planet of all in the Solar system is due to gravitational compression while Mercury is smaller and not as compressed. This leads to the fact that for it to have such high density, the core must be large and rich contain of iron.
Mercury’s core also contains the most iron compared to that of any other major planet in the Solar system. There have been several theories as to why this is so. The most common theory is that the planet originally had a metal-silicate ratio that was similar to common chondrite meteors. These meteors were typical to that of the Solar System’s rocky matter with a mass that is approximately 2.25 more than its current mass. However, during the early years of the Solar System, planet Mercury could have been strucked by a planetesimal of approximately up to 1/6 of that mass. The impact would have destroyed most of the original mantle and crust and only leaving the core as the relative major component.