A Serious Force
Gravity is the force that keeps your feet planted firmly on the ground. It's the attraction between a planet and the objects at its surface. On Earth, we are used to a level of gravity that pulls us in toward the planet, allowing us to walk without floating away. When astronauts are in space, they experience zero gravity, and they have to adjust to a feeling of weightlessness.
Gravity is a tricky thing. Different levels of gravity affect the human body in different ways. In addition to feeling differences in weight and balance, gravity affects the way a person's muscles and bones develop.
Scientists have tracked the changes that occur in human bodies at these two different levels of gravity. But, how will people respond to gravity on Mars? If scientists can learn more about gravity on Mars, they will have a better understanding of how it will eventually affect the humans who go there.
That's where the mice come in. In 2006, a group of mice will be launched into orbit as part of the Mars Gravity Biosatellite Project.
"What we're doing," explains Paul Wooster, a scientist from Massachusetts Institute of Technology, "is developing a spacecraft that is going to spin to create artificial gravity." By spinning 34 times each minute, the satellite will generate the same gravity as Mars. According to Wooster, this marks the first investigation at this level of gravity.
The team of mice will be made up of all females. One of the reasons they decided on an all-girl group, Wooster says, is that females eat a bit less than male mice, so fewer materials need to be sent with them. Within the Biosatellite, the mice will be monitered in individual compartments. They will be exposed to the Mars gravity for five weeks, returning to Earth in a small capsule attached to a parachute.
So how will the mice pass the time in space, once they get tired of the view?
"We may give them a wooden block to chew on," says Wooster. One thing the mice won't have is a wheelexercise is a definite no-no. Studies have shown that when astronauts exercise in low-gravity, the high level of activity works against the effects of low-gravity on the body.
The focus of the project's research is on changes in bone and muscles, as well as changes in the inner ear (which affects a person's ability to balance). Each mouse will have its own environment equipped with a camera to monitor its individual activities. Sensors will read changes in the body, and a water pump will track the amount of water the mice drink.
By studying the effects of the gravity level on the bodies of mice, scientists will have a better idea of how the gravity on Mars will affect human astronauts. These mice astronauts may be tiny, but they're making a huge contribution to the future of Mars exploration.