A spacecraft screams downward through the pink Martian sky. It bounces to rest on the rocky red soil, cushioned by a grape-like cluster of giant white airbags. The airbags are sucked back into the craft, and out rolls a six-wheeled robot. Scanning the terrain with laser eyes, it spies a rock, rolls toward it, and begins to drill…

	Watch a simulation of the 2003 Rover landing on Mars. [Need help?]

No, it’s not the start of a sci-fi thriller. It’s a description of the 1997 Pathfinder mission to Mars. The 22-pound star of the mission was Sojourner, a microwave-sized rover that took pictures, sampled soil and rocks, and relayed information back to earth. Among Sojourner’s findings: clues that Mars may once have been covered with water, water that could have supported microscopic life.

The Mars Autonomy Project The huge distance between Earth and Mars–123 million miles–has a troublesome consequence: commands from Earth take 11 minutes to reach a rover on Mars. Likewise, any new information from the rover–say, a rock looming in its path–takes 11 minutes to reach earth. This delay slows down navigation considerably. Wouldn’t it be great if a rover could find its own way around?     See a 360 degree panorama (1.5MB) of the Mars Rover at Carnegie Mellon University. [Need help?] Researchers at The Mars Autonomy Project are working to develop a rover that can solve its own navigation problems, for example, judging when to steer around rocks or just go over them, and choosing routes that conserve power. The goal is a rover that can travel one or two hundred meters all by itself. It would use stereo vision to produce a digital map of the terrain, then analyze the map to find to shortest, easiest path.

In 2003, robots will return to Mars to finish what Sojourner started. This time, NASA will send two identical rovers to two different locations, places where water is most likely have left its geologic mark on the land. Unlike Sojourner, which communicated through a stationary lander, the new rovers will send and receive signals directly. Like robotic geologists, each will be a 300-pound mobile laboratory on wheels, equipped to gather information and perform tests that will answer questions about Mars’ past.

The Mars rovers are one example of how robots let us explore places we can’t go ourselves. But robots are also exploring right here on earth. The 1912 wreck of the luxurious cruise ship Titanic waited at the bottom of the ocean for 74 years before finally being explored by an underwater robot named J.J. At a depth of 12,500 feet, the Titanic is far too deep to be explored by a human diver. Robots are often called upon perform underwater salvage missions. A minivan-sized robot called The Deep Drone helped recover the black box from EgyptAir Flight 990, which plunged into the Atlantic in 1999.