Mercuryis one of four so-called terrestrial planets in our solar system. Mercury is essentially a dead rock orbiting the Sun. It is a very different type of planet than Earth. After a period of cratering, the interior cooledrather quickly. It is heavily cratered and does not have the large, flat maria which are common on the Moon's Nearside. The features on Mercury are namedafter artists, poets and musicians. It has nothing to speak of in the way of atmosphere, it appears to be geologically inactive, and because of its proximity to the Sun, its surface temperatureis almost high enough to melt some metals. Mercury's iron coreseems to be rather large for such a small sized planet. This gives the planet a relatively high overall density. The spin-orbit couplingof this planet is interesting. This causes the same side of Mercury to face the Sun on every other orbit.Observing Mercury
Mercury has a radius of 2439 km, which is approximately one third of Earth.
Mercury rotates in 58.6 days at the sidereal rate, referenced to the stars. Its synodic day, from noon to noon, is 176 days. There is a 3 to 2 resonance to the rotation and revolution.
Mercury revolves around the Sun in just 88 days.
The atmosphere of Mercury is practically non-existent. There are some captured helium atoms from the Sun, and a very thin cloud of sodium atoms which have been ripped from the surface.
Hey! No atmosphere means no clouds!.
Mercury has no moons
Silly Earthling! Terrestrial planets have no rings!.