The last time such an event occurred, Mongolian conqueror Genghis Khan was still alive, and another pass this close isn’t likely for another 800 years. Of course, it’s all just a trick of the eye, thanks to the fact that astronomers are viewing the planets from Earth.
As the planets Jupiter and Saturn make their historic “great conjunction” on Monday, amateur astronomers are snapping incredible photos of the two gas giants.
In reality, the planets are not physically any closer to each other than they normally are; the conjunction is only possible for a viewer here on Earth, thanks to a perspective phenomenon called “parallax.”
Europa and Titan are both candidates for possible extraterrestrial life, and NASA has proposed missions to both moons to find out.