Mars from Above: Carving Channels
Adapted from selected activities from Mapping Mars, Destination: Mars, NASA Johnson Space Center, 2002, and the Scratching the Surface unit of Explore! Mars: Inside and Out, Lunar and Planetary Institute, 2007.
Carving Channels is a 15-minute activity in which children ages 8–13 create channel features with flowing water, comparing their observations to real images of Mars and Earth taken by satellites/orbiters. Their observations of the ways in which flowing water alters the surrounding terrain are used as clues to draw conclusions about Mars’ geologic past and its ability to support life, as well as how scientists view these features from space.
What's the Point?
- Channels are surface features carved by a flowing liquid, like water.
- The types of features formed by flowing water indicate the slope of the terrain.
- The presence of channels on a planet or moon is evidence that liquid once flowed on its surface and suggests that it possessed an atmospheric pressure high enough that the water was stable as a liquid at the surface (i.e., it would not boil off instantly).
- Scientists are interested in knowing if water is — or was — present on other planets and moons because all life as we know it requires water. If there is or was water, life might be — or have been — present.
- Models — such as the children are using here — can be tools for understanding the natural world.
- Geologists use features on Earth to help them understand how similar features may have formed on other planets, like Mars.
- Use group work and collaboration to help engage children. Girls benefit from collaboration, especially when they can participate and communicate fairly. 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 imagery to think critically about what it is like on Mars (what we can observe) and what that can tell us about its past and potential to support life — now or in the past.
- Provide opportunities for developing spatial skills. Spatial skills are not innate and can be improved with training and experience. This activity provides an opportunity for children to think three-dimensionally, by creating a model and drawing to represent their ideas.
The following materials are for this activity conducted as stations.
For each station: The following materials will serve approximately 8 children working in teams of 3–4. Two “stream tables” are recommended (one per team) for this station, as listed below:
- 10 pounds of clean playground sand
- 4–5 (1" to 3") rocks (2" diameter or less)
- 4–6 (2-liter) bottles, without lids, filled with water
- access to water to refill the bottles as needed
- 2 plastic wallpaper trays (from home improvement or hardware stores) or other long narrow plastic container such as plastic window planter boxes
- 4 standard bricks (foam floral/craft bricks may be used if desired)
- 2 (5-gallon or larger) trash cans or buckets (rectangular shaped is best)
- 2 large trash bags to line the buckets or trash cans
- 1 set of full-page Earth Image Placemats (stream channel images only) from the Mars Match activity
- 1 set of Mars Cards (channel images only) from the Mars Match activity
- optional (recommended): 5 pounds of pesticide-free diatomaceous earth (from a home improvement or pool supply store), gloves, and a mask; the diatomaceous earth will aid in creating well-defined channels
- optional: 1–2 bottles of craft sand, any color (24 oz. — readily available at hobby or department stores) may be used in place of diatomaceous earth
Caution: Diatomaceous earth poses an inhalant hazard and can cause eye irritation if handled improperly. If you choose to use it in your stream tables, set up the stream tables beforehand and keep the diatomaceous earth moist or covered to keep it from becoming airborne in the presence of children. Use caution when working with the diatomaceous earth and setting up the tables. You may use a mask to protect yourself. It is also a good idea to wear gloves when handling this material as it may dry hands significantly.
For each child:
- optional: 1 set of Extreme-O-File: Mars from Above activity pages
- optional: clipboard
- optional: 1 set of Life on Mars? Trading Cards
For the facilitator:
- background information
- scissors or other tool to poke holes though thin plastic trays
- Review the activity procedures, activity pages, and background information.
- Prepare the stream tables:
- Poke 3 pea-sized holes on the bottom of each narrow plastic tray, about 1" from the end. Punch holes only in one end of the trays.
- Place the trays so that the children can easily group around them.
- Tray 1: Pour 2" to 3" of sand into the tray, keeping it away from the end with holes so that the water can drain.
- Partially bury 2 or 3 rocks in the sand, so that the upper 2/3 of the rocks are exposed.
- On top of the sand, pour 2" of diatomaceous earth OR 1" of craft sand.
- Add a thin layer of regular sand across the surface of the diatomaceous earth/craft sand.
- For the top layer, sprinkle just enough diatomaceous earth/craft sand to cover the sand.
- Dampen the sand.
- Tray 2: Pour 2" to 3" of sand into the tray, keeping it away from the end with holes so that the water can drain. Have the sand along the edges a little higher than in the center so water will flow down the center.
- Bury 2 or 3 rocks in the sand.
- Dampen the sand.
- Bury 2 or 3 rocks in the sand.
- Position each plastic tray so that the end with the holes hangs over the table edge about 6".
- Place a lined trash can or bucket under the part of the tray that extends over the edge to catch excess water as it drains from the tray.
- Place 2 or 3 bricks under the other end of the wallpaper tray #1 with the diatomaceous earth/craft sand, so it is tilted about 20°. You may want to recruit help with positioning the trays on the bricks.
- Place one brick under tray #2 with the sand only, so that it is tilted about 5°.
- Fill two, 2-liter bottles with water and place them beside the trays.
- Place copies of the Mars/Earth channel images (from Mars Cards and Earth Placemat set) near the stream tables. You may wish to laminate or put these images into page protectors to protect them from the water during the activity.
1. Consider the images of channels on Mars and Earth. Explain that these images were taken by spacecraft looking down on the planets.
- What do the features look like? Rivers, streams, etc.
- How might channels have formed on Earth? Water.
- What do you think created the channels on Mars?
2. Point out that the trays and their contents are called stream tables, and they contain sand (and possibly diatomaceous earth).
- What do you notice about the way in which the trays are positioned? The trays are positioned at an angle; one tray at a steeper angle than the other.
- Which way does fluid, like water, flow? Water — or any fluid — flows downhill.
- What do you predict will happen when you pour water onto the surface at the top of the tray? The water will flow downhill. It will create channel features much like the ones they observed in the images of Earth and Mars.
- Do you think the features in the steeply dipping tray will differ from the features in the tray tilted 5°? If so, in what way(s)? Answers may vary, but may include that in the tray with a low slope, the water will travel more slowly. The size of the material may also cause a difference. Perhaps the sand will drain more.
- What do you think will happen when the water meets an obstacle, like a buried rock? Answers will vary, but may include that the water will stop, or go around the obstacle.
3. Invite the children to create their own channels! Invite the children to take turns holding a water bottle at the high end of the tray and slowly pouring water, gently and steadily, into each tray.
- What features do you observe?
- Observe what happens along the stream edges. Can you detect sand building out some parts of the meanders and eroding others?
- Optional: Draw your observations and complete the questions on your Extreme-O-File: Mars from Above activity page for the Carving Channels activity.
- Do the channels you created look anything like those in the images of Mars and/or Earth? What is the same? What is different? Try to match one of the images to your channels.
- What happens if you increase the flow rate of the water? Do the features change?
- How do the features in the stream table with the lower tilt compare to the one with the higher tilt?
4. Discuss what the model means in terms of Earth and Mars. Explain that both Mars and Earth have features that look like meandering channels (look at the Mars Match Cards and Earth Image Placemats). Mars also has some features that look like the braided channels and teardrop-shaped islands. We know that features like these are formed by water on Earth. This means that it is likely that the channels that we see on Mars were also caused by flowing water. Using these observations, we can recreate an image of what Mars was like in the past!
Have the children reflect on what they observed and the images from Mars and Earth. Optional: Invite them to record what they learned and to finish completing the questions in their Extreme-O-Files: Carving Channels activity pages (if they have not already).
- What caused the channels in the stream tables to form? Water flowing across the surface cut into the surface and carried some of the material away.
- Do you observe flowing water in the images of Earth’s channels? What do you conclude about how Earth’s channels formed? Flowing water carved Earth’s channels.
- Do you observe water flowing in the channels on Mars? No. What do you conclude about how those channels formed? Water carved the channels but the water is no longer there.
- If you observe channels on a planet, based on your model, what do you conclude about how those channels formed? Water — or another fluid! — created the channels.
- What does this tell you about that planet? Water was once present.
- What do the channels on Mars tell us about the history of Mars? Mars once had flowing water that carved the channels, but there is no evidence of water on the surface today.
- Why might scientists be interested in water on other planets? All life as we know it needs water. If water is — or was — present, there may be — or have been — life!
Summarize that Mars and Earth have been shaped by similar processes, and that we can find stream channels on both planets.