Chasing Mars | Kepler’s Laws & Planetary Motion Investigation

The Description

For centuries, circular orbits seemed like the perfect way to describe planetary motion—until Mars refused to cooperate. This investigation invites students into the evidence problem that eventually led Johannes Kepler to rethink the model.

Through readings, models, eccentricity practice, an observation and triangulation demonstration, and orbital reasoning, students investigate how astronomers could locate Mars and why Kepler's laws mattered. The point is to make sense of the scientific argument, not simply memorize three laws.

What Students Will Do

• Explore how a circular-orbit model struggled to match observations of Mars.

• Model ellipses and eccentricity and interpret changes in orbit shape.

• Investigate how observation positions and triangulation help astronomers infer a planet's location.

• Connect Mars observations and patterns to Kepler's laws of planetary motion.

Why This Resource Is Different

The thing I want students to notice is that a convincing model isn't necessarily a correct one. Chasing Mars starts with the historical evidence problem: circular orbits looked reasonable until repeated observations of Mars wouldn't fit. That conflict gives a purpose to the orbital models and eccentricity work.

Students use readings, scaled representations, and triangulation reasoning to follow the problem scientists were trying to solve. They aren't memorizing three laws in isolation; they're asking why a new explanation became necessary. This is a separate investigation from the Unearthing Mars state-lab pre-lab.

What's Included?

• 21-page Chasing Mars student investigation PDF.

• 37-page teacher presentation PDF.

• Seven-page teacher overview PDF with instructional purpose and teaching guidance.

The Details

Audience: High-school Earth & Space Science or astronomy. Topics: Ellipses, eccentricity, orbital models, triangulation, Kepler's Laws, evidence from Mars. Format: Printable PDFs with teacher presentation and overview. This is a separate investigation from the Unearthing Mars state-lab pre-lab.