Explore! Ice Worlds!

Ice Zones: Where We Look for Ice

Overview

In this 30 minute activity, children, ages 10 to 16, draw conclusions about where on a planetary body scientists might look for ice — and why. They use a clay ball, ice cubes, and a heat lamp to model the permanently-shadowed polar regions of planets and moons that may harbor ice. They learn that our Moon and even Mercury may have areas with ice!

What's the Point?

  • Polar regions of most planets and moons receive less intensive sunlight.
  • Equatorial regions of most planets and moons receive more intensive sunlight.
  • Areas that are in permanent shadow, such as inside craters at the poles of some planets and moons, can maintain very cold temperatures.
  • Ice may exist in these permanently shadowed regions.

Materials

For each group of three to four children:

  • 1 heat lamp or work lamp with a 100 watt or greater light bulb
  • 1 (6" or larger) clay ball or Styrofoam ball
  • 1 paper plate
  • 16 coffee stir sticks or large toothpicks
  • 2 ice cubes of similar size
  • Small Styrofoam or insulated cup or container to keep the ice cubes frozen (optional)
  • Planetary Thermometer
  • Moon's surface images

For the facilitator:

Activity

1. Invite the children to share their ideas about ice.

  • What conditions does ice need to exist? Temperatures need to be cold.
  • Where in our solar system are the temperatures cold? Far from the Sun.

2. Share the Planetary Themometer cartoon with the children.

  • Which planets are cold enough to have ice? Mars, Jupiter, Saturn, Uranus, and Neptune (and Pluto, our favorite dwarf planet).
  • Earth's average temperature is above freezing according to the image. How can it have ice? The image shows average temperatures, so some temperatures can be warmer and some can be colder.
  • Earth is pretty close to the Sun, how can we have cold areas with ice and snow? Children may say that we are just the right distance from the Sun. In fact, Earth is at a distance at which it should be very cold. Earth has an atmosphere that helps regulate our temperatures, acting like a blanket to hold in the heat. Without our atmosphere, the side of Earth facing the Sun in the day would be very hot and the side facing away from the Sun (nighttime) would be very cold!
  • Is it possible that Mercury, or the Moon, which are close to the Sun, have places that are permanently cold? If the children suggest that the side that is facing away from the Sun is cold, they are partially correct, but share that the Moon and Mercury (and other planets) spin on their axes so that the night-time side will eventually become day and become hot.. Share that the Moon and Mercury don’t havean atmosphere to hold in the heat, so their  sides  facing the Sun are HOT and sides that are in darkness are COLD!
  • Are there other places on these planets that might be cold?
  • What regions on Earth are the warmest, e.g. the tropical regions around the equator, the poles, or somewhere else? The equatorial regions
  • What regions on Earth are the coldest? The polar regions
  • Why do the children think this is the case?
  • What about other planets and moons? Do they have warmer equators and colder poles? Other planets and moons are generally warmer at their equators and colder at their poles.
Facilitator's Note:

There are some exceptions. Neptune's axis is slightly tilted, like Earth's, and its south pole has pointed at the Sun for decades — making it the warmest spot on the planet. Curiously, the one planet that orbits the Sun on its side — Uranus — is not warmer at the pole facing the Sun than at its equator. Scientists are still unsure as to why this might be the case. Saturn's moon Enceladus is also warmer at its south pole than at its equator, due to tidal forces from  Saturn. All of these bodies lie far out in the solar system where their temperatures overall are cooler.


3. Provide the children with clay or styrofoam balls, coffee stirrers or toothpicks, and lamps and invite them to explore why the poles are cold and the equator is warm.

  • What could the ball represent for this activity? A planet or moon. In this case, the clay ball will represent our own Moon.
  • What might the lamp be? The Sun.

4. Have the children insert one coffee stirrer or toothpick into the north pole and one into the south pole of their clay Moon so that they are sticking out.

  • What do the coffee stirrers or toothpicks represent? The axis, or north and south poles of the Moon. The axis is the imaginary line that extends from the north pole of a planet through the planet to the south pole. Planets and moons spin — rotate —on their axes.

5. Invite the children to experiment with creating day and night on the Moon's surface using the lamp and ball. Day and night cycles are produced because a planet or moon spins on its axis.

6. Share that, because the Moon has no atmosphere to help control its temperatures, the Moon's daytime side is very hot (about 225°F / 107°C), and the Moon's nighttime side is very cold (about -244°F / -153°C). Areas in the shade during the lunar day are also very cold. Let the children know also that the Moon turns more slowly on its axis than Earth. The lunar day and the lunar night are each about 14 days long.

7. Share with the children that the Moon's axis is almost straight up and down (it’s only tilted  1.5°). This is much smaller than Earth's axial tilt of 23.5°. As they are creating day and night, make sure they hold the Moon so that the north pole is upright and not tilted.

  • Which part of the Moon gets  the most sunlight: the top, the middle, or the bottom? At the middle —the equator; the light is the "strongest" or most intense.
  • Which part of the Moon will have the shortest shadows? Which part will have the longest shadows?

8. Invite the children to add the rest of their toothpicks or coffee stirrers to their Moon in a line stretching from the north to the south lunar pole. They should be spaced evenly, and sticking out, with one at the equator of their Moon.

9. Darken the room lights and invite the children to shine their “Sun” lamp at their Moon from two to three feet away, so that the center of the beam of light is aimed at the Moon's equator, then slowly turn their Moon.

  • What do they observe about the shadows cast by the coffee stirrers or toothpicks? The toothpick at the equator has the shortest shadow. The toothpicks near the poles have the longest shadows.
  • Are there any parts of the Moon that are shielded from the Sun? Even at the low levels of incoming — "incident" — sunlight, the polar regions receive some light.

10. Have the children brainstorm some ideas about how they might create places that are permanently in shadow on the Moon’s surface. Share the images of the cratered lunar surface.

  • Are the craters lit by sunlight as the Moon spins on its axis?
  • Are there places where craters may be lit and places where they may not be lit?

11. Invite the children to create craters in their moons by poking half-inch-deep holes, including one in the north.

  • When they shine the “Sun” light on their Moonand turn the Moon, what do they observe about the light in the cratered regions?
  • Is there a difference between craters at the pole and craters at the equator? Craters across much of the surface are illuminated by the light, but the bottoms of craters at the poles stay dark all the time.
  • What does this mean for the temperature in the craters that stay dark? These craters do not receive any light or energy from the Sun, so they are very cold.

Scientists have found evidence for ice in some of the deep, dark, cold craters at the Moon's north and south poles, at at  Mercury’s poles.

  • Where might the ice have come from? Can the children think of any small icy bodies in our solar system that may occasionally run into a planet or moon? Comets! Scientists have evidence that comets do strike planets (we observed Comet Shoemaker- Levy hitting Jupiter!). These comets can bring water and ice to the planets they strike.

12. Tell the children that two comets are about to strike their Moon. Provide the groups with two ice cubes. Have them place once in a crater at the north pole and one in a crater at the equator. Make sure to push the ice cubes into the ball so that they are beneath the surface with the tops of the cubes exposed. This will help them stay in place.

  • Which ice cube will melt faster when the  “sunlight” (from the lamp) reaches the planet: the ice cube at the pole or the one at the equator?

13. Invite the children to illuminate their Moon, holding the lamp about 5 to 6 inches from the surface, for about three minutes. The child holding the Moon should hold it so that his or her fingers are as far from the ice cubes as possible.

  • Where is the sunlight more intense? The middle of the Moon, at the equator.
  • What affect do they think this is having on the ice cube that is at the equator?
  • What about the ice cube at the pole?

The children may notice that the ice cube at the pole is melting slightly. This is not the case for ice in permanently shadowed regions on the Moon!

14. After three minutes have the children remove the ice cubes and examine them.

  • Do they see a difference in the size of the two ice cubes now? The ice cube at the equator melted more and should be significantly smaller.
  • Why did this happen? The ice cube at the equator received more intense sunlight (from the lamp). The ice cube at the pole received less intense sunlight.

Conclusion

Have the children reflect on where ice might be in the solar system based on what they know about ice and what they have learned in the experiment.

  • What does ice need to exist on a planet? Temperatures that are sufficiently cold.
  • What planets have surface temperatures that are cold enough for ice?
  • Are there planets that are "too hot" — too close to the Sun — to have ice?
  • On these planets, might ice exist? If so, where? Why?