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Changing theories about Mars

Levels: 5-6
NoS achievement aims: Understanding about science icon. Understanding about science
Contextual strands: Planet Earth and beyond icon. Planet Earth and beyond
Topic: Space


Mars has the largest volcano in the solar system (Olympus Mons), and a huge canyon system (Valles Marineris), but no canals.

Once thought to be home to life forms that built canals, the current view is that Mars is unlikely to host life. Keeping open-minded about new information allows scientists to fully explore options. Open-mindedness is important to the culture of science.

What you need

  • Access to resources about the surface of Mars, as well as books and Internet resources.
  • Large sheet of paper or wall space for mapping out a timeline.

Note: Supporting activity resources are provided below.


  • What stories do you know about life on Mars?
  • Where do ideas about near-space objects, like Mars, come from?
  • What do you think it is actually like on Mars?
  • How do you decide which information to believe about Mars?
  • Do all scientific discoveries lead to an improved understanding about Mars?


  1. Get students to share their ideas of what they have heard about the possibility of life on Mars.
  2. Give them a copy of The story behind life on Mars .
  3. As a class, devise a plan to develop the resource into a large timeline (for example, a wall chart), making sure the design allows room to add further information.
  4. Get the students to pose questions about any further information they'd like to know about the surface of Mars, and/or the events on the timeline.
  5. Some questions (see also Reflection) might be:
    • Where have the ideas about life on Mars come from? Why did people think there might be life on Mars? How did scientists check those ideas out?
    • What is the same/different about the surface of Mars and of Earth?
    • Does Mars have an atmosphere that might support life?
    • Have them research and investigate answers to their questions, using print, web resources, and the Mars versus Earth resource supplied, and add the results to the timeline.
    • Have them research and investigate answers to their questions, using print, web resources, and Mars versus Earth (page 2, The story behind life on Mars ), and add the results to the timeline.
  6. Alternatively, or as an extension, get students to:
    • hold a debate for/against the existence of canals on Mars
    • develop a drama or role-play of the development of ideas about possible life on Mars.


  • What evidence helped open-minded scientists change their minds over the last 20–30 years about what is on the surface of Mars?
  • How was that evidence gathered?
  • How easy do you think it has been for scientists to remain open-minded enough to shift their theories about Mars, when there were so many stories around that captured the popular imagination?
  • Why do scientists now think life on Mars is unlikely?
  • What conditions would be needed to support life on Mars?
  • How does research about life in extreme environments on Earth help us with our understanding of the likelihood of life on Mars?

Activity resources

Word icon. The story behind life on Mars (Word 32 KB)

  • The various ideas about Mars mapped out in a timeline and a chart comparing Mars and Earth.