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