Purple Earth Hypothesis suggests Earth was once a purple planet. Early microbes used retinal, not chlorophyll, for ...

Mars will rise in the eastern sky during the night, and can look a ruddy red color in telescopes and binoculars. (If you're looking for gear to see the planets, check out our best telescopes guide ...

A special planetary alignment is occurring in January and February. Four planets are visible to the naked eye, with two more faintly showing. Here's how, where, and when to see the planets line up — ...