Mars: The Feature Story
What's the Point?
1. Invite the children to examine the picture (map of Mars).
- What is this picture showing? Answers will vary. Many children will think this is a map showing water and land because of the colors.
- Is this Earth? No.
- What planet might this be, given what they have been investigating? Mars!
- Does water exist on Mars? No. What might the map be showing? Height of the land, or elevation. This is a topographic map of the surface of Mars.
- What colors are the low areas on Mars? Refer the children to the scale. The low areas are blue. The high areas? Red and yellow and white.
2. Invite the children to share what they observe about the map. As they make their observations, invite them to show the feature or pattern they are talking about with the group by pointing it out on the map. Observations may include that:
- There are mountains or volcanos
- There are craters
- The top or northern part of the map is deeper or lower than the bottom or southern part of Mars
- The bottom or southern part has more craters or is more rough
- The top has fewer craters or is more smooth
- The mountains or volcanos occur in just a few places
- There is a bump or bulge on the surface where there is a cluster of mountains or volcanos
3. Prompt the children to link their earlier investigations to the features.
- How do craters form?
- How do volcanos form
- If a planet has volcanos, what does that tell us about the planet? That it is still — or has been recently — hot enough inside to melt rock and make lava.
- Do they see any evidence of flowing water on the map that might look like the features they formed in their stream tables? Prompt the children to look carefully at the areas where the highlands in the south (reds, oranges, and yellows) transition to the lower region in the north (blues and purples). There are some broad channels and teardrop shaped islands that look something like the features they created when they had steep, fast flowing water. Unlike the craters and volcanos, the channels that they observed in images in previous activities are very small compared to the scale of the map. There are only a few places where the channels are large enough to be observed.
4. Encourage the children to draw conclusions about the surface of Mars.
- How did the southern half (hemisphere) of Mars become so rough and cratered? Lots of impactors — like asteroids — hit the surface.
- Do you think the impactors hit only the bottom half of the planet? No, impactors come from all directions, and all locations of a planet or moon are equally likely to being hit by them.
- Which is an older surface, the cratered southern part or the smooth northern part of Mars? The cratered southern part because it has more craters. Because planets get hit all over with impactors, when geologists see smooth regions on a planet's surface, they interpret that something happened after it was cratered to smooth it out or cover it up. It is important to note that the entire planet of Mars is very old (4.56 billion years old!), and cratered but some of the old surfaces have been covered by younger, more recent, happenings.
If the children have difficulty with this idea, ask them to imagine a sheet of mud in a rainstorm. Early in the rainstorm, when only a few drops have fallen, there will be only a few raindrop patterns in the mud. With time, as the storm continues, more and more raindrop imprints will be left in the mud. The older a planet surface is, the more raindrop/impact craters it will have. After the storm, you have a mud sheet peppered with raindrop imprints; imagine taking a bowl of mud and pouring it across half of the sheet. In the area where the new mud was poured, the imprints will be filled in/smoothed over by a newer surface.
- What might have caused the northern part of Mars to become smooth? Answers will vary, but may include that it was eroded, that water smoothed it, or that lava filled it in.There is evidence that, below the surface, the northern hemisphere is just as cratered as the southern hemisphere. Scientists are debating why there is such a difference between the southern and northern regions of Mars, and what happened to smooth the surface of the northern region.
- Can you find any other areas besides the upper half of Mars that also appear smooth? Yes, the area surrounding the volcanos.
- What does this tell them about the age of the volcanos? That they are young, because they are not very cratered.