Mercury

Mercury is an innermost/inner planet, (planets made of rock and metals) that is almost as big as Australia. Mercury's surface is gray at visible wavelengths. Mercury was tidally locked that is kept one face always to the Sun just as the Moo keeps one face to the Eath. This led to the idea that one of the coldest places in the Solar SYstemj might be the permanent dark face of Mercury the planet close to the Sun. Mercury in fact turns on its xis once every 59 days, exactly two third of the 88 days it takes to go aruiond the SUn. Regardless, the planet's lack of an atmosphere to circulate warmth around.