To compare the orbits of Earth and Mars, use double-sided tape to secure a large, yellow ball to the floor. This will represent the sun. Looking at the "sun' as the center of large clock, mark with masking tape the 12, 3, 6 and 9 positions in a circular orbit around the sun. Make a larger, ellipse-shaped orbit for Mars. It should swing out farther between Earth’s 3and 9 positions. Divide Mars’ orbit into eighths. Get a friend to be either Earth or Mars and begin to orbit starting at the same place. For every one-quarter orbit Earth travels, Mars travels one-eighth orbit. Mars is not visible when Earth finishes the first orbit, because it is on the opposite side of the sun.
If you regularly watch Mars in the night sky, it appears to become brighter every two years. Draw the orbit of Earth as a circle, and then draw the orbit of Mars as an ellipse around Earth's orbit so that every one-quarter orbit of Earth is equal to one-eighth orbit of Mars. When Mars is the closest to Earth, it appears brighter. The tilt of Mars is about the same as that of Earth, but its orbit takes it farther from the sun, making the planet colder at this time and giving it seasons.
Missions to Mars launch around the time the planet is closest to the Earth. This cuts down on the distance traveled, but distance is not the only challenge. Mars and the Earth are moving in different orbits, and both planets are spinning. To simulate the difficulty of sending a rocket to Mars, take some balls and a bucket to a park with a manually operated merry-go-round. Put the bucket 9 to 12 feet away, stand on the merry-go-round and toss a ball into the bucket. Jump off the merry-go-round, start it spinning, jump on and try to toss a ball into the bucket again. Mars is also spinning, so imagine trying to toss the ball into a bucket spinning on another merry-go-round.
Plan a trip and design a Mars habitat as though you are a crew member for a mission to Mars. List all of the things the crew needs to sustain life. Determine how they will grow crops, what fuel sources will be available, where the crew will obtain water and air and how they will dispose of waste.