Begin by engaging the class in a discussion about colonizing Mars. Ask whether they think it is possible and how they imagine the journey to Mars and life on it would be. Encourage children to be as creative, imaginative and descriptive. Although creativity is to be encouraged, work to consolidate knowledge the children have already acquired about Mars by asking questions such as whether they would be able to breathe, what they would eat and drink, etc.
Ask the children to write a piece about colonizing Mars. This doesn't have to be a simple story, but could instead be a diary entry or a postcard home after the colonization. Again, encourage children to be as descriptive and creative as they can, but ensure that their writing remains true to the facts they have learned about Mars. Allowing children to imagine potential ways to overcome problems such as lack of oxygen and water supply consolidates knowledge of Mars while encouraging problem solving and creativity.
This activity complements science lessons relating to the solar system particularly well. However, the project could also include art, asking children to draw or paint postcards. It also could involve drama if they wished to write and act out a play about colonizing Mars.