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80 Modern Robotics

ISSUES: SHOULD WE SEND PEOPLE OR ROBOTS TO EXPLORE THE
UNIVERSE?

Many critics of the space program argue that human presence in space
is a luxury and a waste of resources if we truly want to learn as much as
possible about the solar system. While spectacular, the manned Apollo
Moon landings did not bring back data that could not have eventually
been gathered by robot explorers and sample return missions. The
expensive International Space Station and the dangerously unreliable
space shuttles that served it have returned little scientific benefit. As of
2006, both programs appear to be in trouble and facing an uncertain
future.
During those same few decades, robotic explorers have visited every
planet in the solar system except Pluto. Landers and rovers have begun
an extensive exploration of Mars. Missions such as Galileo and Cassini-
Huygens have probed the giant planets Jupiter and Saturn, landed on
the mysterious moon Titan, and even impacted a comet to see what
kind of material lay under its surface. (In January 2006, the Stardust
probe returned a cannister of comet dust to Earth for study.)
When humans travel in space, the bulk of the resources and effort
has to go to keeping them alive and healthy. A round-trip journey
to Mars would take several years, during which time the astronauts
would have to be supplied with food, water, and air and protected
from the hard radiation of space. Long-term weightlessness also has

communications with Earth. As Shirley noted in her autobiography,
Sojourner was programmed to keep trying to make contact:

On Sol 87 [Sojourner’s computer] would have ordered her to start
circling the lander, constantly checking, trying to hear a signal. We all
had a sad image of the little rover rolling jerkily around the lander like
a lost child, calling “Hello? Hello? Is anyone listening?

In 2004, Sojourner’s larger and more gifted children, the rov-
ers Spirit and Opportunity, landed on Mars. While Sojourner had
covered a total distance about equal to the length of a football