NASA Astronomy Picture of the Day Collection

Southwest Mercury

The planet Mercury resembles a moon. Mercury [ http://seds.lpl.ari…]'s old surface is heavily cratered [ http://antwrp.gsfc.…] like many moons. Mercury [ http://bang.lanl.go…] is larger than most moons but smaller than Jupiter [ http://antwrp.gsfc.…]'s moon Ganymede [ http://antwrp.gsfc.…] and Saturn [ http://antwrp.gsfc.…]'s moon Titan [ http://antwrp.gsfc.…]. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth [ http://antwrp.gsfc.…] is the only planet more dense. A visitor to Mercury's surface [ http://antwrp.gsfc.…] would see some strange sights. Because Mercury [ http://www.oulu.fi/…]rotates exactly three times every two orbits around the Sun [ http://antwrp.gsfc.…], and because Mercury [ http://nssdc.gsfc.n…]'s orbit is so elliptical, a visitor to Mercury [ http://antwrp.gsfc.…] might see the Sun [ http://antwrp.gsfc.…] rise, stop in the sky, go back toward the rising horizon [ http://antwrp.gsfc.…], stop again, and then set quickly over the other horizon. From Earth [ http://antwrp.gsfc.…], Mercury's proximity to the Sun [ http://antwrp.gsfc.…] cause it to be visible only for a short time [ http://www.maths.qm…] just after sunset or just before sunrise.

Mariner 10 [ http://nssdc.gsfc.n…], NASA [ http://www.nasa.gov/]

Ganymede

Arizona

Mercury

Saturn

Jupiter

Goddard Space Flight Center (GSFC)

Earth

Ganymede

Moon

Sun

Mercury

Saturn

Jupiter

Mariner

Mariner 10

Titan

http://antwrp.gsfc.…

SPD-APOD-ap960913