In 2006 a group of mice-astronauts will orbit
Earth inside a spinning spacecraft. Their mission: to learn what
its like to live on Mars.
by Karen Miller
Humans need gravity.
Without it, as astronauts have vividly demonstrated, our bodies
change strangely. Muscles lose mass, and bones lose density. Even
the ability to balance deteriorates.
From long experience
on the space shuttle and various space stations, we have some knowledge
of how mammals, especially people, respond to 0-g. We have even
more experience with 1-g on Earth. But we still don't know what
happens in between.
What, for example,
will happen to humans on Mars where the surface gravity is 0.38-g?
Is that enough to keep human explorers functioning properly? And,
importantly, how easily will they readapt to 1-g, once they return
A team of scientists
and students from the Massachusetts Institute of Technology (MIT),
the University of Washington, and the University of Queensland,
in Australia, plans to explore these questions. They're going to
do it by launching mice into orbit.
"What we're doing,"
explains Paul Wooster, of MIT, and program manager of the Mars Gravity
Biosatellite project "is developing a spacecraft that is going to
spin to create artificial gravity." The satellite will spin at the
rate of about 34 times each minute, which will generate 0.38-g -
the same as gravity on Mars.
The team hopes to
launch the Biosatellite in 2006. The mice will be exposed to Mars-gravity
for about five weeks. Then, says Wooster, they'll return to Earth
alive and well. The mice will descend by parachute and land near
Woomera, Australia, inside a small capsule reminiscent of NASA's
old Apollo capsules.
The Biosatellite project
is the first investigation conducted at this gravity level, says
Wooster. Financed in part by NASA, the project is also unique "due
to the heavy involvement of students in all aspects of the work,
including planning the science, designing the spacecraft, raising
the funds, and managing the overall effort," he adds.
The research will focus
on bone loss, changes in bone structure, on muscle atrophy, and
on changes in the inner ear, which affects balance. "The main thing
we're trying to do," says Wooster, "is to chart a data-point between
zero-gravity and one-gravity."
artist's rendering of the Mars Gravity Biosatellite in
As they orbit the earth,
the mice, each in its own tiny habitat, will be painstakingly observed.
Each habitat will have a camera, so that the researchers can monitor
mouse activity. Each will have its own pump-driven water supply,
so that each mouse's water consumption can be tracked.
Each mouse's wastes
will be collected in a compartment beneath its habitat; the compartment
will contain a urinalysis system checking for biomarkers that indicate
Each habitat will also
be equipped with a body mass sensor, which will take frequent readings.
This will also allow the researchers to track how the weight of
the mice changes over the course of the five weeks.
Each mouse will also
have toys to keep it busy. "We may give them a wooden block to chew
on," says Wooster. That'll keep them happy, and will also prevent
them from chewing on the habitat. They might have a small tube to
No wheels, though,
says Wooster, because NASA has learned that exercise can counteract
some of the effects of low-gravity on astronauts. A mouse with a
wheel in its cage can actually run several miles a day. "We don't
want to give the mice a countermeasure in terms of exercise."
The students will be
using only female mice, says Wooster. That's partly because female
mice eat slightly less than male mice, decreasing the mass that
must leave Earth. But more importantly, some studies suggest that
females are affected more strongly by lowered gravity than the males.
Those studies, though,
weren't conducted in true partial gravity. Rather, they were done
by suspending the hind legs of the animals, so that the mice are
only able to feel part of their weight on the ground. The simulated
Mars gravity inside the Biosatellite will be much more realistic.
of the Mars Gravity Biosatellite is still on the drawing
board. Shown here is a cutaway design diagram of a mouse
habitat for the spacecraft.
Through the three participating
universities, more than 250 students have been involved in the Biosatellite
project. The project is being led and coordinated by MIT, which
is also managing the animal habitats and life support systems. The
University of Washington is in charge of providing electrical power,
propulsion, attitude control, thermal control, and all the communications
to the ground. The University of Queensland is in charge of the
entry, descent, and landing systems, including the heat shields
"I think that one of
the big contributions of the Biosatellite," says Wooster, "is the
educational benefit for the students involved." So many people,
he says, have been inspired by this project, and have learned from
it. "Plus we're going to be getting back information that nobody's
ever had before, data that have been missing in the planning of
human missions to Mars."
How might humans respond
to gravity on Mars?
With the successful
landing of NASA's rover Opportunity, that question seems closer
and closer to one we'll need to solve.