Education and
Public Engagement
at the Lunar and Planetary Institute
Explore! Life on Mars

Searching for Life

Adapted from “It’s Alive!” from Destination: Mars, NASA Johnson Space Center, 2002.


In this 45–60-minute indoor activity, children ages 8–13 discuss how life is defined and conduct a simple experiment, looking for signs of life in three different “soil” samples. The experiment introduces the children to the difficulty that scientists face in defining life. By observing the soil samples, the children try to determine if any contain signs of life and work to identify, refine, and create a set of characteristics that may be used to identify living versus nonliving things. The activity concludes with the development of a group definition of life. This group definition will be important, and should be referred to as the children work through the subsequent module activities (if they are undertaken).

This activity complements the later Mars Engineering activity and can be combined with a presentation by an astrobiologist, planetary scientist, or NASA Solar System Ambassador, if desired. It is highly recommended that this activity be preceded by the Ice Breaker activity.

What's the Point?

Tips for Engaging Girls in STEM:
  • Use group work and collaboration to help engage children. Girls benefit from collaboration, especially when they can participate and communicate fairly. Girls are energized by the social part of science, working and learning together. This activity gives the children the opportunity to collaborate and work together in a fun and engaging social environment.
  • Encourage critical thinking. Girls gain confidence and trust in their own reasoning when encouraged to think critically. This activity provides an opportunity for children to use their observational skills and think critically about identifying signs of life.
  • Expose girls to female role models who have achieved in math and science in order to promote positive beliefs regarding women’s abilities. If possible, have a female speaker share the science of astrobiology, and how scientists look for life in the universe. This activity also provides activity pages, Scientist Spotlight pages, and Trading Cards featuring female (and male) astrobiologists as an additional resource to connect children with careers in science and to challenge existing stereotypes of scientists.



For each pair of children:

For each child:

For the facilitator:


Note:  Make sure to use a different stirring stick/spoon for each type of cup (A, B, and C) to avoid cross-contamination.

Suggested books


Divide the children into small groups of 2–3 children each.

 1. Welcome and introduce the topic/module. Explain to the children that in this activity, they are going to discuss how we define life and conduct an experiment to test for the signs of life (much like a rover on Mars may do) – creating a group definition of life to use in later activities. Having a clear definition is important for scientists, too. In order for a rover, like the Curiosity rover on Mars, to find signs of life, scientists need to have a clear understanding of what to look for — how to identify living versus non–living!

2. Ask the children what the characteristics of life are. Invite the children to work in their small groups and then to share their answers and examples. Write their responses on the White Board/Poster/Chalk Board.  Optional: You may write their responses on colorful Post–It ® notes and post them on a poster or wall.

As a group, you should work to create an initial definition for life together that they will use as they move on to complete more of the Explore: Life on Mars? activities. Optional: Have the children record their definition (set of characteristics) on their Extreme–O–File activity page. Note: If you have previously conducted the Ice Breaker activity, you should incorporate the characteristics compiled during that activity here and add to them/refine them.

3. Invite the children to conduct an experiment searching for signs of life in three different “alien” samples, based on the characteristics they defined. Pass each small group the 3 prepared cups A, B, and C, and a copy of the Extreme–O–File: Searching for Life activity page.

4. Invite the children to add hot water to their samples. Pass around the hot water to the children and ask them to add the water to each cup, filling it up halfway (to completely cover the sand and leave some water on top). Alternatively, fill the cups to the appropriate level for them. Note: Caution them to be careful while handling the hot water.

After a few minutes…

5. Discuss the definition of life with the children, while the water continues to react with the materials in the cups. Discuss the scientific perspective on life, and consider how life might be different on other planets. Encourage all ideas, and write their responses on the flip chart/white board.

Facilitator’s Note: Share that scientists do not agree on exactly how to define life; it is a difficult subject. Machines can be built to make other machines, computers can be programmed to learn, and cars also need fuel and use energy and move. One of the most basic definitions that may be applied is that life does something and keeps on doing it (while living).

Observe any further changes in the “alien” samples. Ask the children to observe their three cups again and record their last observations.

Describe the ingredients for each cup, and for each cup, ask whether the sample contained life. Describe the yeast sample last. Let the children know that yeast is a fungus that was growing, using the sugar and giving off carbon dioxide, which created the foam. While they could not see the yeast itself (it is microscopic), they were able to observe signs of life, such as the foam and gas bubbles. They may have also noticed that the cup was getting warmer — another sign of life from the yeast. Scientists suspect that any life present on Mars would have been (or is) microscopic (i.e., too small to see with the human eye). Thus, scientists need to observe for signs of life much like the children have just done!

Revisit the group definition/set of the characteristics of life. Do you have any changes or additions to make to your definition? If so, add/change as needed. Have the children record it their findings in their Extreme-O-File activity pages.

Facilitator’s Note:

Studying (unicellular) yeast cells, such as those in the experimental cup C, has provided many scientific advances in biology over the years. Yeast has even made it into space to study the effects of microgravity. In fact, researchers today are using yeast to help understand the development of multicellular life forms that exist on Earth today, alongside the unicellular forms. By understanding how life developed on Earth, they hope to understand how life may have developed beyond our planet.

For more information about how yeast is being used to study the origin of life, please visit

In Conclusion

Ask the children whether it was difficult to identify the soil sample with life. If so, why? Which of their senses were most useful as they were observing? Note that scientists use instruments to make observations. For example, they can use instruments that measure the chemical composition of air as a remote form of “smell” on another planet (like Mars). Did the children use their noses and notice any differences between the “soil” samples during the activity?

Summarize the experiment and its results. How did this experiment affect and help you to create your group definition of life? 

Share that, while at first it might seem like determining if something is alive or not is easy, defining life is actually much more difficult than many people realize. Optional:  Have the children record the group definition in their activity pages.

Revisit your refined group definition. Explain how an experiment may be used in missions (such as their rovers) to search for signs of life in other places, such as Mars. By refining our understanding of life, we are better able to look for it elsewhere. This is what astrobiology strives to do!

Defining life is not a simple task and even scientists do not completely agree on all the characteristics that should be used to do so. Tell the children that they will refine their group definition as they continue to explore the possibilities of life on Mars in the later activities.