Question 1
Multiple choiceHard1 markFor one star, a model places the Goldilocks zone—the orbital band where surface conditions could permit liquid water—at 1.20–2.00 × 10¹¹ m. A survey retains a site only if it is in this band, has liquid water and shows the expected solubility pattern for known hydrophilic and hydrophobic probes. Which site should be retained?
| Site | Orbital distance / (10¹¹ m) | Water observed | Hydrophilic probe in water | Hydrophobic probe in water |
|---|---|---|---|---|
| A | 1.50 | Liquid | Dissolved | Dissolved |
| B | 1.70 | Ice | No liquid sample | No liquid sample |
| C | 1.80 | Liquid | Dissolved | Undissolved |
| D | 2.20 | Liquid | Dissolved | Undissolved |
Show answer and explanation
Answer: C. The modeled zone spans 1.20–2.00 × 10¹¹ m, so site C at 1.80 × 10¹¹ m is within it. Its sample is liquid, with the hydrophilic probe dissolved and the hydrophobic probe undissolved, matching water’s solvent properties. Many hydrophilic molecules dissolve in water, and most enzymes catalyse reactions in aqueous solution, so these observations support a possible medium for metabolism, but do not establish that life is present.
A: the location and liquid water fit, but dissolution of the known hydrophobic probe does not match the expected solvent pattern.
B: being in the zone does not make ice a liquid aqueous medium for enzyme catalysis.
D: the solvent observations fit, but 2.20 × 10¹¹ m is beyond the survey’s zone.
Remember: the Goldilocks zone makes surface liquid water possible; it does not guarantee water or life.