Mars and Life Evidence

Overview

In this lesson (Lesson 12 of 20) students explore why Mars is a target for life-search missions and analyse evidence scientists use to make claims about past or present life. Students practise planning and justifying an investigation idea by identifying variables, assumptions, and possible sources of error.

Learning intentions

• Students will discuss the purpose of Mars exploration and how evidence guides scientific claims.
• Students will analyse a range of evidence (photos, rover data summaries, and secondary information) to decide what it can and cannot prove.
• Students will identify assumptions and sources of error that may affect conclusions about life on Mars.
• Students will construct a short evidence-based argument evaluating a claim about Mars having conditions suitable for life.

Success criteria

• I can explain what counts as evidence when scientists look for life on Mars.
• I can state a testable question and a hypothesis about how one factor could affect habitability.
• I can identify variables and assumptions for a simple, reproducible investigation model.
• I can write a claim-supported-by-evidence conclusion and explain at least one possible error or limitation.

Curriculum links

• Students plan and conduct reproducible investigations by identifying variables, assumptions, and risks where appropriate, including ethical considerations about accessing and using information.
• Students analyse methods, conclusions and claims by identifying assumptions, possible sources of error, conflicting evidence and unanswered questions.
• Students construct evidence-based arguments to support conclusions and evaluate claims, considering ethical issues and cultural protocols when using or citing secondary data.
• Students apply scientific thinking about causal relationships (e.g., how a changed condition could influence a measurable outcome in an analogous model).
• Students develop investigable questions, reasoned predictions and hypotheses.

Lesson structure (30 minutes)

1. 0–5 min · Hook: “What would count as life?” Teacher displays 3 evidence cards (examples: “organic molecules detected”, “liquid water features”, “today Mars is cold and dry”) and asks: “Which pieces of evidence are strongest for life, and why?” Students choose one card, then write one sentence: what the evidence suggests and one limitation.

2. 5–12 min · Direct teach: evidence vs claims Teacher explains how scientists move from observations to claims, focusing on: evidence quality, assumptions, and what alternative explanations could look like. Teacher models an example claim: “Mars once had conditions suitable for life.” Students annotate an anchor chart: Evidence → Reasoning → Assumptions → Possible errors/limitations.

3. 12–20 min · Guided analysis: assumptions and sources of error Teacher gives a short scenario with conflicting information (e.g., “A sample shows signs that could be organics” but could also be contamination; or “features suggest water” but may not prove it was liquid long enough). Students in pairs (or teacher-led if needed) complete a “Claim–Evidence–Assumption–Error” table for one claim:

• What is the claim?
• What evidence supports it?
• What assumption is required?
• What source of error or alternative explanation is possible?

4. 20–27 min · Small investigation plan (model for habitability) Teacher introduces a simple analogous investigation idea students can plan without needing lab materials (or with minimal materials if available): “Does water availability affect growth/survival of living things?” (Students use the idea only as a model of habitability conditions.) Students write a mini-plan (3–4 sentences) including:

• investigable question,
• hypothesis,
• one independent variable, one dependent variable, and one controlled variable,
• one assumption and one risk/safety note (if any materials would be used).

5. 27–30 min · Exit ticket: evidence-based argument Teacher prompts: “Select one evidence card and write a 5–6 sentence argument: claim, evidence, reasoning, limitation, and unanswered question.” Students submit their exit ticket.

Resources

• 3 evidence cards or printed summary sheets about Mars exploration findings (teacher-prepared)
• Anchor chart template: Evidence → Reasoning → Assumptions → Possible errors
• “Claim–Evidence–Assumption–Error” table worksheet
• Mini investigation planning template (question, hypothesis, variables, assumption, limitation)
• Exit ticket template (5–6 sentence argument frame)
• Whiteboard/markers or slideshow with the evidence cards (no hyperlinks needed)

Assessment

• Formative checks during the hook: sentence about evidence suggestion and limitation.
• Formative worksheet review: accuracy in identifying claim, evidence, assumptions and possible errors.
• Exit ticket: quality of evidence-based argument (claim supported by evidence; includes limitation/unanswered question).

Differentiation

• Support: provide sentence starters for the assumption and error sections (e.g., “This assumes that…”, “A possible error is…”).
• Support: offer a narrowed choice of evidence cards (e.g., only 2 options) for students who need reduced cognitive load.
• Challenge/extension (within the lesson): ask students to propose an additional piece of evidence that would reduce uncertainty for their claim.
• If students require language support, allow responses to be partly scaffolded using the frames and a word bank (evidence, claim, assumption, limitation, uncertainty, variables).