Mars Missions Slow in April, Thanks to Sun's Position

It's the Martian version of spring break: Curiosity and Opportunity, along with their spacecraft friends circling overhead, will take it easy this month because of the sun's interference. For much of April, the sun blocks the line of sight between Earth and Mars. This celestial alignment—called a Mars solar conjunction—makes it difficult for engineers to send instructions or hear from the flotilla in orbit and on the surface. Such communication blackouts occur every two years when the red planet disappears behind the sun.

Mission teams prepared by uploading weeks of scaled-back activities beforehand. "They're on their own," says a NASA scientist. The rovers are banned from driving. Instead, they take a staycation and study their surroundings. The orbiting Mars Odyssey and Mars Reconnaissance Orbiter continue to listen for the rovers and make their own observations, but for the most part will transmit data once Mars is in view again. (More Mars stories.)