On Jan. 4, a strange sight unfolded on the planet Mars. Above a vast, dry lake bed south of the Martian equator, a conical vehicle parachuted toward the surface. Just before touching down, it was enveloped by a gigantic protective airbag, allowing the craft to bounce safely to a stop. Inside were Spirit and its twin, Opportunity, the most sophisticated rovers ever launched from Earth. “Mars Dead or Alive,” from the PBS television series NOVA, covers this mission in depth, providing a behind-the-scenes look at the rovers’ construction and culminating with the latest news and images from the red planet. The original broadcast aired last month, but the entire program is available for viewing online. Visitors to the site will be able to watch an animation of Spirit’s journey from Earth to Mars; examine the robotic geologists and their scientific instruments; create a parachute both strong and light enough to safely slow the rovers in their descent toward Mars; and see some of the finest images ever taken of the Martian surface.