Initial Publication Date: September 24, 2025

The Moon pcMEL

The Moon pcMEL asks students to weigh the connections between evidence and alternative explanations about the formation of the Moon. Understanding how the Moon formed supports understanding of Earth's formation and early history.

The Models

Model A: The Moon is an object that came from elsewhere in the solar system and was captured by Earth's gravity.
Model B: The Moon formed after a large object collided with Earth and material from both combined to create the moon.

Student Handouts


Lines of Evidence

Evidence #1: Earth's average density is higher than the Moon's. The density of Earth's crust is a little lower than the Moon's, but Earth's density increases toward the core.
Evidence #2: Simulations of other star systems show that planets form when smaller objects collide.
Evidence #3: The Moon's orbit around Earth is tilted compared to the planets' orbits around the Sun.
Evidence #4: Earth is about 35% iron, most of which is in the core. The Moon has very little iron.


Student Handouts

Virtual MEL

*NOTE: The virtual materials below are from an older version of the activity than what is posted above.

The Google Drive folder below contains MEL resource documents in the Google formats. In order to maximize the flexibility of our activities, the MEL Project Team wanted to make more resources compatible with virtual settings. We have made our MEL scaffolds available in Google formats, so that they can be copied, modified, and uploaded more easily on a variety of platforms and devices. Please note that to access all the materials for each MEL scaffold, you will need a Google account. View the README file first.