A Safe Crew T ere are many dangers in space. One danger is radiation. It is a form of energy that can harm people. It can cause cancer and even kill people. Luckily, spaceships do block some


radiation. Spacesuits block more of it, but not all. Something stronger needs to be invented. Engineers are working on this problem now.


A Healthy Crew T ere are other problems astronauts face, too. Long trips in space can weaken bones. On Earth, bones stay healthy when muscles pull on them. T e muscles fight against gravity. T ere is no gravity in space. So bones grow weak. Astronauts are already testing a


new exercise machine. It makes the astronauts feel like they are pushing against gravity. Scientists are also studying a new


medicine. It will keep bones from becoming weak.


Picking the Right Crew It’s important that the crew members get along, too. T ey’ll be cooped up together for a long time. T ey might become restless. T ey may argue. Yet all of the astronauts need to


get along. If something goes wrong, they will have to find a solution. It would take too long to get help from Earth. T e crew needs to handle emergencies together.


GRAVITY is a force that causes two objects to pull toward each other. The gravity on Mars is a little over a third what it is on Earth. So a person would weigh a third as much.


The surface of Mars, as seen by the rover, Spirit.


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