Swathed head to toe in surgical garb and huddled over a table, George Nakatsukasa slowly places a sturdy cover over the electronic heart of his six-wheeled patient. Across a room so clean it contains almost no dust, dozens of engineers are circling a second robot, peering beneath layers of aluminized plastic at the thick ropes of cable emerging from its torso.
The quiet focus in this room at NASA's Jet Propulsion Laboratory contrasts starkly with the commotion and media glare encircling Johnson Space Center in Houston -- where the loss of the space shuttle Columbia has brought manned spaceflight to a grinding halt.
The challenge of space exploration now has fallen heavily to the engineers at JPL, who have been working for more than a year at a breakneck pace to send twin handcrafted robots to Mars.
The assembly and testing of these sophisticated vehicles has been under intense time pressure from the start. The breakup of Columbia came as engineers in Pasadena were in a last, difficult stretch: the push to finish the rovers and send them to Florida for launch this summer. The team has had little time to pause, let alone grieve.
When he heard the news about Columbia nine days ago, Nakatsukasa stopped in his tracks. Then he headed into work. He had to. New hardware was waiting to be installed.
"We can't slow down," said Nakatsukasa, a lead technician with the team building the rovers. "We've got a launch window to meet."
The Mars craft will be ferried into space separately in May and June, not by a shuttle but by Boeing Delta II rockets.
JPL's mission of robotic space exploration is detached enough from the astronaut program that the accident provided no reason for delay. In fact, the crash only strengthened the resolve of many at JPL.
"Explorers don't back off," said JPL Director Charles Elachi, who called an "all-hands meeting" of employees the Monday after Columbia disintegrated over Texas, killing the seven astronauts aboard.
"I told them the best thing you can do to honor the astronauts is go back to your offices and work on this."
Delaying the $800-million mission to determine whether Mars could have once sustained life is not an option, because the launch window opens only once every 26 months.
By examining chemical and mineralogical clues hidden within Martian rocks, the "robot geologists" will seek proof that the water necessary for life once was present in large amounts on the now-cold planet's surface.
There are more ambitious plans -- to drill into the Martian surface, embed equipment to provide a continuous stream of data and images and bring rocks back to Earth for analysis.
But they depend on what is learned during this trip and future missions scheduled for every launch opportunity over the next 15 years.
The pressure for this mission to succeed -- already high because of the loss of two Mars spacecraft in 1999 -- has increased since the Columbia tragedy.
"It added pressure, and we were already as committed and as pressured as possible," said Randy Lindemann, the lead engineer responsible for designing the rover.
"Like a team that lost a few outings and now faces a bigger game, we've got to win."
A small rover was supposed to fly in 2001, but that trip was canceled after an independent review of the 1999 failures criticized NASA for trying to do too much on what amounted to a shoestring budget. Instead, officials decided to wait and attempt a more challenging mission, using the two rovers.
As the mission evolved, the rovers themselves became much bigger. At 368 pounds, they eclipse the Sojourner, which at a diminutive 25 pounds landed on Mars in 1997 after its launch in 1996 aboard the Mars Pathfinder. The new Mars exploration rovers can travel up to 100 yards a day -- the distance Sojourner did in its entire three-month mission.
"Basically, this is a robotic geologist in an SUV," said Mark Adler, the lead landing engineer.
The twin explorers are packed with high-tech instruments and hardware that make them seem eerily human. The camera, with binocular 20/20 vision coming from two separate "eyes," stands about 5 feet off the floor.
A 3-foot-long arm with a shoulder, elbow and wrist for flexibility will be able to scratch the surfaces of weathered rocks and then analyze the rock interiors with a microscope just as a geologist would.
Three spectrometers -- or chemical analyzers -- will study elements, minerals and compositions of rocks to look for evidence of past water and try to determine what conditions on Mars may have been like when the rocks formed.
The rover cameras will send back images so clear and colorful, "they would look good projected on an IMAX screen," said Steve Squyres, a Cornell University geologist in charge of the rovers' science instruments. "These are going to show you Mars like you've never seen Mars before."