Lesson 6 of 6 · Choose the measurement that changes the answer
Choose the measurement that changes the answer
10 minute lesson · 3 checks along the way
Your goal for this lessonDesign a feasible observation that distinguishes two explanations of a Martian landscape.
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Turn a broad interest into a test
“Was Mars ever wet?” is an important starting question, but many observations already support ancient liquid water. A productive next question identifies an unresolved mechanism, place, or time. Did a mineral form while sediment accumulated in a lake, or when groundwater later moved through fractures? Both involve water, yet they predict different relationships between mineral deposits and the rocks surrounding them.
Write the alternatives before choosing an instrument. A lake-deposition model might predict a mineral distributed along particular sedimentary beds. A later groundwater model might predict concentrations along fractures cutting across those beds. These are simplified expectations, not universal rules: a site can record several episodes. The aim is to collect evidence that changes the comparison, including evidence that would make your preferred explanation less convincing.
Work through a decision
Work the evidence: spend the observing time
For a fictional investigation, you have ten observing credits. A regional context map costs three, and a chemical map across a selected bed–fracture intersection costs seven. Another global portrait costs ten. Your two models currently fit the regional appearance equally well but predict different mineral distributions at the intersection. Which package addresses their disagreement most directly? The context map plus chemical map uses all ten credits and targets the discriminating relationship.
A chemical map without context would be harder to interpret, while an impressive global portrait might add little to this particular comparison. Record the expected outcomes in advance. A mineral following fractures across several beds favors later fluid movement over a simple bed-confined deposition model. A result following beds would favor the other simplified explanation, while mixed patterns could require a sequence containing both episodes.
Check 1 of 3
10 pointsUse the reading above. You can try again without losing points.
Make the test representative and achievable
A spectacular target that cannot be approached safely may yield less usable evidence than an accessible exposure that tests the same idea. Slopes, loose material, communications, energy, and available instrument reach constrain fieldwork. Orbital observations from missions such as Mars Express help place local targets in a regional map. Surface explorers, including Tianwen-1 / Zhurong, illustrate how a mobile platform investigates a much smaller accessible area.
Do not confuse the photograph of a rover with a measurement of all the surrounding ground. A camera’s view extends beyond an instrument’s actual . After a first test, compare multiple intersections and control locations away from the proposed feature. If mineral enrichment appears everywhere, the fracture association may disappear. Repeating observations that can fail your model is more informative than selecting only its strongest-looking examples.
Zhurong and the Tianwen-1 landing platform photographed by the mission’s deployable remote camera. This frame, preserved from China News Service’s published video, shows surface hardware and its immediate surroundings.
Look closely
Does the visible expanse of ground equal the area that a contact instrument has chemically sampled?
See what to notice
No. A camera can show terrain beyond the location actually measured by another instrument. The picture documents a rover and lander in their surroundings; sampling coverage must come from a location log and instrument footprint, not from everything visible in the frame.
Check 2 of 3
10 pointsUse the reading above. You can try again without losing points.
Let results reshape the question
A useful report separates what was observed from what was inferred and what remains uncertain. You might conclude that a mapped mineral association supports later alteration at one outcrop while leaving its regional extent unknown. That narrower statement gives the next team something concrete to test. It also preserves room for new evidence without discarding the measurements that motivated the earlier interpretation.
Mars exploration becomes a connected investigation when landscapes guide sampling, instruments test composition, and results reshape environmental models. A negative detection can be informative if the experiment was sensitive enough to detect the predicted signal; otherwise it may simply expose a limit. Future work should follow the uncertainty that matters most, whether that means another location, a different instrument, or a better model. The best next question earns its place by making a possible answer scientifically consequential.
Check 3 of 3
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Put it together
Your lesson progress
Each check connects to a part of the story. Complete all 3 to earn your 25-point lesson bonus.
Go to the source
Explore the evidence behind this lesson. These optional readings and videos open in a new tab.
- Read: NASA: CheMin and environmental evidenceDifferent mineral identities and geological contexts constrain past environments.
- Read: ESA: Arabia Terra from Mars ExpressRegional imaging provides a different scale of evidence from a local sample.
- Read: NASA JPL: following the carbonate evidenceLocal detection leads to testable questions about deposits elsewhere.