Mercury is 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 cooled rather 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 named after 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 temperature is almost high enough to melt some metals. Mercury's iron core seems to be rather large for such a small sized planet. This gives the planet a relatively high overall density. The spin-orbit coupling of this planet is interesting. This causes the same side of Mercury to face the Sun on every other orbit. Observing Mercury
Carpe Caelum Planetary Astronomy
Carpe Caelum Planetary Astronomy