Mars has gotten so big in recent weeks that even a backyard telescope will show details on the planet’s surface: dust clouds, volcanic terrains, impact basins. Best of all is the polar ice cap. The southern hemisphere of Mars is tipped toward Earth and its bright southern cap, which reflects more sunlight than any other part of the planet, is remarkably easy to see.

Don’t wait too long to look, though, because the ice is melting. Like Earth, Mars has seasons that cause its polar caps to wax and wane. Lately, for instance, amateur astronomers using 8-inch and larger telescopes have been watching a frosty mountain range emerge from the ice.