Explore! Marvel Moon

Time Travelers

Adapted from the Lunar and Planetary Institute's interactive website and associated classroom activity, Evolution of Our Solar System Timeline.


Children, ages 8–13, embark on an exploration of Earth's and the Moon's shared history in this 30 –minute introductory activity for the Explore! Marvel Moon module. They work in groups to determine the order of geologic events  — such as the formation of the Moon and when the bright crater of Tycho formed — and arrange images depicting those events in the correct order. The children are introduced to NASA lunar scientists, who are currently investigating the Moon's history, through comic-book style visualizations of their real-life work. Finally, the children share their own histories by drawing, comic-book style, a past connection with the Moon in their own lives.

What's the Point?

  • The Moon shares Earth's long history, from the formation of the Moon through a giant impact to the Apollo Moon landings in the 1960s and ‘70s.
  • NASA lunar scientists are working together to understand the history of our Moon. They each bring unique skills to the effort.
  • The Moon has inspired diverse personal connections.


Facility needs:

  • A large room, hallway, or sidewalk
  • Optional: wall space for creating a library display with the timeline

For each group of 11 children (or up to about 30 children working in teams):

  • Optional: white board, or poster paper and markers, or chalkboard and chalk, to record the children's ideas
  • One set of Event Cards (11 total events), preferably printed in color on card stock, for 11 individuals or small groups to sort
  • Optional: 1 timeline of the universe's history, prepared as described under "Preparation" using:
    • 1 (185') roll of butcher's twine
    • Measuring tape (preferably 50')
    • 3 signs, made from sheets of colorful paper marked with the following terms:
      • Today
      • Solar System Forms
      • Big Bang
  • Art supplies, such as colored pencils, crayons, and markers

For each child:

For the facilitator:


  • Review the background information.
  • Print the Event Cards, preferably in color on card stock. Shuffle them into random order.
  • Provide a space for the children to move around as they determine the order of the event cards and form a human timeline.
  • If desired, provide wall space for the children to post the event cards and feature the timeline as a library display.
  • If desired, prepare a timeline to help the children visualize the Big Bang's relative place in history. Unroll the twine measure out 40 feet; tie a knot and tape the "Solar System Forms" sign there. Tape the "Today" sign at the end (i.e. the end nearest the knot). Uncoil the twine and tape the "Big Bang" sign at the beginning.
  • Display several books about the Moon in a place where the children can page through them before and after the activity. Be prepared to direct the children to books about other key topics mentioned in this activity, such as dinosaurs, asteroids, and anthropology.
  • You may wish to split mixed ages of children into two age groups: 8–10–year–olds and 11–13-year-olds. The older children may be more familiar with the events and be able to sort them more quickly than the younger group. If possible, invite another adult or teenager to work with the younger children to place their cards as they work separately to assemble the single timeline.

Facilitator's Note: Earth and the Moon are companions in space, and experienced many similar events over their long, shared history due to their proximity to one another.

  • The components of our solar system all formed at the same time — and formed quickly! The planets formed 4.56 billion years ago, and the Moon formed 30 to 150 million years later.
  • Scientists hypothesize that the Moon formed as a result of a planetary body, about half the diameter of Earth, striking Earth approximately 4.5 billion years ago.
  • Earth and the other inner, rocky planets of our solar system were dominated by physical activity for much of their early history (formation, bombardment by asteroids and comets, volcanism, formation of layers — core, mantle, crust; formation of atmospheres, in the case of Earth and possibly Mars, formation of oceans).
  • The inner planets are cooling. Small bodies, like the Moon, essentially are geologically inactive because they have cooled; they no longer have interiors hot enough to produce volcanic activity and to release atmospheric gases at the surface.
  • Scientists hypothesize that the planets and moons of our inner solar system underwent a period of intense bombardment by asteroids.  This created the large, circular craters we observe on the Moon. This period ended approximately 3.9 billion years ago.
  • Even though the period of intense asteroid bombardment ended almost 4 billion years ago, smaller, less frequent impacts continue occur on all planets and moons. Such impacts can influence Earth's biosphere.
  • The biosphere got underway ~1 billion years after Earth formed, but was dominated by simple life forms for a loooooooooong time.
  • Dinosaurs went extinct 65 million years ago, and most scientists agree that a single, large asteroid impact was the cause.
  • Modern humans — Homo sapiens — appeared only recently with respect to geologic time.

Asteroids played an important role in shaping the histories of both Earth and the Moon. They struck the Moon throughout its history, creating the "holes" we still see on its surface today. They also struck Earth — even more frequently because Earth's greater gravitational pull attracted more asteroids — and one impact is famous for ending the dinosaurs' reign.


1. Assemble the children in a group and invite them to share what they know about the Moon. If desired, keep track of their ideas on poster paper. It is not important to correct the children’s ideas, rather this activity should encourage them to explore and learn more.

  • When was the last time you saw the Moon? Was it during the day or night?
  • What does the Moon look like?
  • Does its appearance in the sky change over time?
  • What is it made of? Rock.
  • How big is it compared to Earth? Compared to the Sun or other familiar solar system objects?
  • Is the Moon important to you in your life? How? Answers will vary.
  • How old do you think the Moon is? Accept all answers.
  • Do you think that dinosaurs looked at the Moon? Accept all answers.
  • How do you think it formed? Accept all answers.

2. Optional: Set the stage for the children’s investigation into history by showing them a simple timeline of the universe's history. The children may suggest that the "Big Bang," or the event that formed the universe, is related to the Moon's formation.Have two or more children help you demonstrate that a long period of time separates the Big Bang and the Moon’s formation.

2a. Have the children stretch out the first 40 feet of butcher's twine (they may need to stand along the walls of the room in order to get the entire length to fit). One child should hold the end of the twine with the attached "Today" sign facing outward. The other should hold the twine at the knot with the attached "Solar System Forms" sign facing outward. Coil the remaining twine next to his or her feet.Invite the group to imagine that the length of twine represents the entire history of our universe.

  • When did our solar system form? At the knot marked "Solar System Forms."
  • When did Earth form? Discuss all ideas and then reveal then answer: when the solar system formed, along with the other planets.
  • When did the Moon form? Discuss all ideas and then reveal then answer: shortly after the solar system — including Earth — formed.
  • Where does the extinction of the dinosaurs fall on this timeline? Discuss all ideas and then reveal then answer: About a foot before "Today."
  • Why does the twine keep going beyond the knot? What happened before our solar system formed? Accept all answers.

2b. Show the children the "Big Bang" sign at the beginning of the coil, then explain that scientists understand that the universe began from an immense explosion long, long ago (14 BILLION years ago). Emphasize that our solar system which includes all of the planets formed much later.

2c. If desired, use the white board or poster paper to write down the children's ideas about the different events on the timeline.

  • How would you describe the universe? EVERYTHING! Old. BIG.
  • How would you describe the solar system? The solar system is made up of the Sun and eight planets (as well as comets and asteroids).

Facilitator's Note: You may wish to clarify some terms:

  • Universe: all matter and energy.
  • Solar system: One small part of the universe, including our Sun and eight planets.
  • Big Bang theory: The scientific theory used to describe the formation of the universe. While our own solar system's formation was certainly an important event, it lacks a catchy title. Many children — and adults — misapply the term "Big Bang" to the formation of our solar system.
  • Scientific theory: Scientists don't use the word "theory" like people do in casual conversation, as in "Oh, that's just a theory...". A scientific theory is supported by enough evidence to serve as a guiding principle until a better explanation is developed!

2d. Congratulate the children on modeling a timeline of the entire history of the universe! Have everyone return to their seats.

3. Explain to the children that they will be investigating the history of Earth and the Moon — and it is up to them to determine the order of major events! Provide each child or small group with an event card.If you have less than 11 children present, distribute the cards among evenly among them so that each child has a few cards. If you have a very small group, you may wish to order all the cards together. With a large group, invite up to three children to work together with a single card. Invite the entire group to work together to determine which events happened first, second, third, and so on. Have them arrange themselves as a human timeline across the room or along a hallway or sidewalk. (If fewer than 11 children are present, have each child hold up to two cards or tape them along a wall.)

4. Guide the children with the logic behind ordering the events. For example:

  • Which of these events occurred 8-13 years ago? “Your Birth Year!”
  • Which of these events had to have happened first, before the Moon and life could form? "Planets Form."
  • Who has the "Tycho Crater Forms on the Moon, Dinosaurs Watch" card? Who has the "Dinosaurs Go Extinct" card? Which of these cards came first? Dinosaurs watched Tycho Crater form before they went extinct.

Facilitator’s Note: Dinosaurs — and their demise due to an asteroid impact — captivates many children. Direct the children to the library’s resources about dinosaurs and asteroids to help them explore further.

5. Once everyone has placed themselves in order, compare their results to the actual timeline provided in the Master List of Events. Help the children reason through any events that need to be re-ordered. Once the timeline is in correct order, you may wish to have the children read the descriptions of their events and hang the cards along a wall as a library display. Compare the changes on the Earth and Moon over their history and connect related events where possible.

  • Where can geologists find information about the early Earth and Moon? Moon rocks.
  • How did events on Earth relate to the Moon's history? A giant impact between a young Earth and a smaller planetary body threw up a ring of debris into orbit. The material in this ring then clumped together (accreted) to form our Moon. Asteroids and comets struck the Moon and the Earth throughout their history. Early in their history, 3.8–3.9 billion years ago, especially frequent and large impacts created the Moon's largest features we see on the Moon's surface  the large circular impact basins. Homo sapiens — our species — first appeared 150,000–200,000 years ago, and later, humans walked on the Moon!
  • How do the children think scientists learn about events so far back in time?

6. Introduce the children to real time-travelers: lunar scientists! Provide each child with a copy of the Marvel Moon comic book. Explain that since no one can really travel back in time, NASA scientists work as a team to create a timeline of events on the Moon. Invite the children to read about six scientists who will share their team's science through the Explore! Marvel Moon module of activities. They will find that computer models, astronomy, geology, chemistry, and careful observations of planetary surfaces  including those of the Moon allow the scientists to understand ancient geologic history of our Moon and Earth.

7.  Invite the children to look back into their own histories and remember a story about the Moon. Provide each child with a copy of the Moon Stories comic panel. They may wish to illustrate, comicbook style, their first memories of the Moon,or they may feature a lunar scientist looking at the Moon. Instruct them to add the panel as the next page in the Marvel Moon comic book by clipping the book together at the upper left corner. Have them use the art supplies to color their comic books and ask them to bring their comic books with them to each program. They will collect additional pages during the activities. After completing the last activity in the module, My Take on the Moon, they will staple the pages together into complete masterpieces to show their families!


Regroup the children and ask them to share their earliest memories of the Moon.

  • Are the children still inspired by the Moon? Are they curious about any of the events in Earth's or the Moon's history?

Invite the children to return for an investigation of the giant impact that formed our Moon in Wham! Moon!, where they can collect the next pages for their comic books.

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