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It is the smallest planet in the Solar System, with an equatorial radius of 2,439.7 kilometres (1,516.0 mi). [4] Mercury is also smaller —albeit more massive—than the largest natural satellites in the Solar System, Ganymede and Titan. Mercury consists of approximately 70% metallic and 30% silicate material.
Mercury, being the closest to the Sun, with a weak magnetic field and the smallest mass of the recognized terrestrial planets, has a very tenuous and highly variable atmosphere (surface-bound exosphere) containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a combined pressure level of about 10 −14 bar (1 nPa ). [2]
The outer planets Jupiter, Saturn, Uranus and Neptune, compared to the inner planets Earth, Venus, Mars, and Mercury at the bottom right The four outer planets, called giant planets or Jovian planets, collectively make up 99% of the mass known to orbit the Sun. [g] All four giant planets have multiple moons and a ring system, although only ...
The geology of Mercury is the scientific study of the surface, crust, and interior of the planet Mercury. It emphasizes the composition, structure, history, and physical processes that shape the planet. It is analogous to the field of terrestrial geology. In planetary science, the term geology is used in its broadest sense to mean the study of ...
Outline of Mercury (planet) The following outline is provided as an overview of and topical guide to Mercury: Mercury – smallest and innermost planet in the Solar System. Its orbital period (about 88 Earth days) is less than any other planet in the Solar System. Seen from Earth, it appears to move around its orbit in about 116 days.
Mars is the fourth planet from the Sun. The surface of Mars is orange-red because it is covered in iron (III) oxide dust, giving it the nickname " the Red Planet ". [21] [22] Mars is among the brightest objects in Earth's sky, and its high-contrast albedo features have made it a common subject for telescope viewing.
The first probe to visit Mercury was Mariner 10. View of Mercury from Mariner 10 in March 1975. The exploration of Mercury has a minor role in the space interests of the world. It is the least explored inner planet. [1] As of 2015, the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury.
Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine-and-a-half times that of Earth. [26] [27] It has only one-eighth the average density of Earth, but is over 95 times more massive.