But an army of expendable, spherical probes might do the trick, Boston says.
In theory, the units could spring over small gaps and or kick their way out of cracks and crevices.
Boston thinks the bots could also tackle challenging surface terrain on the red planet, including polar ice caps riddled with fissures.
(See photos of Mars.)
Dubowsky says his team at MIT has already developed a prototype that works in the lab.
The mostly plastic bot features an extendable foot powered by an artificial muscle.
Dubowsky has already used the novel "muscle" polymer in other robots.
In the case of the hopping Mars microbots, the plastic muscle would propel the units three feet (one meter) a minute.
The bots could carry any one of a suite of sensors, but the sensors need to be sufficiently miniaturized. Other key systems also remain unfinished.
Dubowksy says researcher Fritz Prince is working to develop a smaller fuel cell for the bots at Stanford University in Palo Alto, California, and that an artificial intelligence system for the machines must still be developed.
The team says "distributed intelligence" is crucial to the microbot concept.
The bots have to "make decisions as an ensemble to figure out how to get around without direct human intervention," Boston said.
In theory, with shared decision-making power, the loss of one or many individual bots would not impair the remaining group or jeopardize the mission.
Constant communication through a local cellular network would further boost the bots' effectiveness.
"They would share information and share decision-making," Dubowsky said.
If a bot found "something particularly interesting, it might call the others in the local neighborhood," he said.
"So you could explore very, very large areas with the flexibility to do deep, detailed exploration if something very interesting came up."
Boston is currently exploring options for deploying the bots. She says the devices could likely withstand a crash landing in a capsule or be driven to a starting point by a rover.
Likewise, a plane or balloon could drop the bots from above.
Dubowsky added, "On various planets you'd like to explore large areas. These would give you the ability to fan out."
The researchers say they hope to test their bots in a cave system on Earth sometime in the next year.
NASA has no plans at present to send the devices to Mars. But the idea appeals to the development team.
"For the same mass and weight that [the Mars rover] Spirit took, you could send a thousand of these to Mars," Dubowksy said.
"You could go into places that you would not dare take one or two rovers."
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