As many of us broil in August heat the Mars rover Spirit is hunkered down to survive a far more brutal season—a Martian winter. Spirit's been on Mars since January 2004 and already survived previous winters, which run from May through November. With sunlight reaching Spirit at a weak angle, the rover hibernates and uses the scant solar power to recharge batteries and heat itself to -40 degrees. At least that's what's happened in previous winters. This winter, the game little unit just doesn't have enough juice to keep its heaters on, so temperatures inside the rover will plunge to a frigid -67 degrees Fahrenheit. When NASA scientists began signaling Spirit on July 26, they hoped to receive a communications beep back—but so far there's only silence. The researchers say that in about two months sunlight will start to increase again through March 2011.