Block 3: Mars as Calibration: What Does Earth Have That Mars Doesn't?
Comparison table: Earth (1 AU, magnetic field, thick atmosphere, liquid water surface) vs. Mars (1.52 AU, no global magnetic field, thin atmosphere, frozen water).
Task: Which row is most important for habitability? Defend in one sentence.
Answer in your Field Notebook, dated.
I can name three differences between Earth and Mars relevant to habitability, explain why Mars lost its atmosphere, and apply the habitability framework to identify where Mars fails.
I can show how one change on Earth sets off feedback loops that change other Earth systems.
"Analyze geoscience data to make the claim that one change to Earth's surface can create feedbacks that cause changes to other Earth systems."
Where this runs:
- U1 B2: Earth as Baseline: Systems Thinking + Subsystems
- U1 B3: Mars as Calibration: What Does Earth Have That Mars Doesn't? ← you are here
- U1 B7: Habitability Framework: Building the Comparison
Assessed:
Goldilocks Report: framework criteria with feedback reasoning, esp. field 5 'where it can fail' (K/U, Component 1 locks U1 Block 7)
On track looks like:
You can run the perturbation test on a loop and say whether it amplifies or stabilizes, and your framework uses that move on real criteria.
Feedback Loops handout (in Google Classroom) · The Systems Diagrammer · Reading: Four Spheres, One System
I can model what is inside Earth, and explain how heat moving through it drives what happens on the surface.
"Develop a model based on evidence of Earth's interior to describe the cycling of matter by thermal convection."
Where this runs:
- U1 B2: Earth as Baseline: Systems Thinking + Subsystems
- U1 B3: Mars as Calibration: What Does Earth Have That Mars Doesn't? ← you are here
Assessed:
Goldilocks Report: the geosphere and magnetic-field criteria (K/U, Component 1 locks U1 Block 7)
On track looks like:
You can say what each layer is, how we know it is there without anyone having been down, and why a liquid moving core is what produces a magnetic field.
I can check an AI's answer against real sources and decide: use it, fix it, or bin it.
In brief: "Evaluate whether an AI output should be accepted, revised, or rejected (paraphrased; full framework at ailiteracyframework.org)"
Where this runs:
- U0 B1: Welcome + How We Work
- U0 B2: OPVL Across Source Types
- U0 B3: AI as a Source + Documentation Protocol
- U0 B4: Source Dossier Launch + Choosing Your Topic
- U0 B5: Source Dossier Work Day 2: AI Source + Documentation
- U1 B1: Phenomenon Launch: What Makes a Planet Habitable?
- U1 B3: Mars as Calibration: What Does Earth Have That Mars Doesn't? ← you are here
- U1 B5: Exoplanet Detection: Transits and What They Tell Us
- U1 B6: Reading Exoplanet Data Cards: Choosing Your Planet
- U1 B7: Habitability Framework: Building the Comparison
- U2 B3: Rivers as Landscape Sculptors
- U2 B6: Field Photo / Map Analysis Work Day
- U2 B7: Reading the Landscape: Worked Example + OPVL
- U4 B5: IPCC AR6 Deep Dive + Chennai Climate Brief Assigned
- U4 B6: Climate Models: How They Work, How They're Wrong, How to Read Them
Assessed:
Every AI Documentation Template: the 'one thing the AI got wrong' field
On track looks like:
You catch specific errors ('it said 2024; the report says 2023'), and you've stopped writing 'AI can hallucinate.'
What today is about
Mars is the failed-habitable case. Today we use it to test our framework.
Four billion years ago, Mars had a thicker atmosphere than Earth has today, liquid water carving river valleys on its surface, and a global magnetic field. The riverbeds, deltas, clay minerals, and sulfate deposits are still there; we can see them. Then Mars lost all three. The question is how, and the answer chains together every framework criterion you're building this unit.
The chain: Mars is smaller than Earth, so its iron core cooled faster. By about 4.1 billion years ago its magnetic field collapsed. With no magnetic field to deflect the solar wind, Mars's atmosphere was stripped over hundreds of millions of years. Thinner atmosphere meant less greenhouse warming and lower surface pressure, both required for liquid surface water. With no liquid water at the surface there was no carbon-silicate weathering thermostat. The climate fell into a stable frozen state. Habitability isn't a property; it's a balance, and Mars lost it.
Today's move is calibration. A habitability framework that classifies Earth and Mars identically is broken (Mars isn't habitable). A framework that says only Earth could ever be habitable is also broken (Mars almost certainly was, briefly). The framework should classify Earth as MEETS, Mars as FAILS or PARTIAL on most criteria, and explain why Mars fails with a mechanism, not just "Mars is cold." Today also introduces the Planet Hunter, an exoplanet-focused Socratic tutor that asks before it tells and never gives habitability verdicts. Read its opening message on the partner page before your first conversation.
Before you start the work
Keep these open. They are the reference data and the tools for today's framework calibration. Notes go in your Class Notebook as a Power outline.
Taking notes? Power 1 seeds for today
| Criterion | Earth (today) | Mars (today) | Mars (~4 Gya) |
|---|---|---|---|
| Distance from star | 1.00 AU | 1.52 AU | 1.52 AU (same) |
| Atmospheric pressure | 101 kPa | 0.6 kPa (~0.6% of Earth) | 0.5–1.0+ bar (estimated) |
| Surface temperature | −89 to +57 °C (mean +15) | −143 to +35 °C (mean −60) | Liquid water possible |
| Magnetic field | Active (25–65 μT) | Absent globally; crustal remnants only | Present (paleomagnetic evidence) |
| Surface water | 71% liquid, all three phases | Subsurface + polar ice; trace vapor | Dendritic valleys, deltas, riverbeds |
Today's work: choose one path
Three real paths, same destination: Mars classified against at least 3 of your framework criteria.
Open your Class Notebook and type today's entry header as Heading 2:
A: Sep 9 | U1 B3 | Mars as CalibrationB: Sep 8 | U1 B3 | Mars as Calibration
What you're submitting today
Mars classification artifact: feeds Step 3 of your Goldilocks Report.
At minimum 3 framework criteria, each labeled MEETS / PARTIAL / FAILS for Mars, with one-sentence reasoning that names the mechanism. Photo of the causal-chain diagram or your written classification.
Submit via Google Classroom (link posted in August)One question before you leave
Three to five minutes. Your answer is saved to your reflection journal, where you can read back everything you have written this year.
Mars as a window onto Earth's possible futures.
Today's reflection is in Google Classroom, under Reflection Journal.
Link posted in AugustSign in with your school account. Your teacher can see what you write here.