On January 3, 2004, a compact rover named Spirit, cushioned inside a pyramid of balloons, hurtled through the martian atmosphere and crash-landed on the dusty surface of Mars. Minutes later, Spirit sent its first message home. The elation of the assembled scientists, along with the much more involved engineering story leading up to the landing, were captured by NOVA producer Mark Davis in his popular documentary MARS Dead or Alive. That elation is the starting point for the sequel, Welcome to Mars.

Welcome to Mars follows the Mars rovers Spirit and Opportunity from the second they crash-land on the planet to many months into their ongoing mission. Davis covered the story from NASA's Jet Propulsion Laboratory as it unfolded and provided a unique, behind-the-scenes take on this voyage of discovery, whose primary goal is to find evidence that liquid water once existed on Mars.

The mission has had its share of drama. The first two weeks after Spirit's landing were euphoric, with fantastic new images arriving every day. But just a few weeks into its mission, Spirit suddenly went silent" and then, inexplicably, started spewing gibberish. For three agonizing days Spirit's engineers worked around the clock, trying to regain control of the unhinged rover. In the darkest hour, many feared that Spirit was doomed. Then, just hours before Opportunity began its own fiery plunge to the surface of Mars, engineers finally discovered the problem" a simple memory overload" and saved Spirit from an early death.

The unfolding science has been equally compelling. With Spirit back up and running, the scientists turned their attention to the arrival of its twin, Opportunity. After tearing through the martian sky and bouncing on the surface for several minutes, Opportunity rolled into a small, shallow crater at the site called Meridiani. Early the next day, the first color postcard arrived, and the scientists were stunned to see an outcrop of layered bedrock just a few yards away. Bedrock is the holy grail of geologists, holding an unambiguous record of geological history. This was the first martian bedrock ever photographed at close range.