Each airbag has double bladders to support impact pressure and, to protect the bladders from sharp rocks, six layers of a special cloth woven from polymer fiber that is five times stronger than steel. The fiber material, Vectran, is used in the strings of archery bows and tennis racquets.

Batteries and other components that are not designed to survive cold martian nights reside in the warm electronics box. Nighttime temperatures may fall as low as minus 105 C (minus 157 F). The batteries need to be kept above minus 20 C (minus 4 F) for when they are supplying power, and above 0 C (32 F) when being recharged. Heat inside the warm electronics box comes from a combination of electrical heaters, eight radioisotope heater units and heat given off by electronics components.

The computer in each Mars Exploration Rover runs with a 32-bit Rad 6000 microprocessor, a radiation-hardened version of the PowerPC chip used in some models of Macintosh computers, operating at a speed of 20 million instructions per second. Onboard memory includes 128 megabytes of random access memory, augmented by 256 megabytes of flash memory and smaller amounts of other non-volatile memory, which allows the system to retain data even without power.

"Gusev is a big hole in the ground, a crater, and it's got this huge dried up river bed flowing into it," Squyres said. "Now if you can come up with an explanation that says there wasn't a lake there, I'd like to hear it. I mean it was water and it flowed into a hole in the ground.