Answer: mercury

AnswerCrossword Clue
MERCURYPlanet nearest to the sun
mercuryThis metal or one of its compounds used medicinally, esp. to treat syphilis
mercurya metallic element
mercuryThe column of such metal in a thermometer or barometer, or its height as indicating atmospheric temperature or pressure
mercuryThe chemical element of atomic number 80, a heavy silvery-white metal that is liquid at ordinary temperatures
MERCURYNearest planet to the sun
MERCURYBarometer filler
MERCURYIt orbits the sun in 88 days
MERCURYHermes, to Horace
MERCURY60's space project
MERCURYFirst mission to put an American astronaut in space
MERCURYEcologists' concern
MERCURYElement from cinnabar.
MERCURYPlanet nearest the sun.
MERCURYGod of science.
MERCURYSun's immediate neighbor
MERCURYFirst rock from the sun
MERCURYThermometer element
MERCURYIt falls in winter