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A1.1.7 (HL)—Extraplanetary origin of water on Earth

Earth’s water may have arrived partly through water-rich asteroids, while suitable planetary temperatures allowed vapour to condense and remain as liquid water.

Syllabus
First assessment 2025
Objective
A1.1.7
Level
HL

Exam analysis

Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paper—
Typical marks1

Common command terms

  • Identify

Scoring notes

Common mistake
Treating asteroid delivery as the only accepted source of Earth’s water.

Recent exam appearances

November 2025Paper1A HL · TZ32[ 1 ]A1.1.7 (HL)—Extraplanetary origin of water on Earth
Practice this objective

Coverage 2025–2025 · Updated 14 Jul 2026

Concept essentials

  • Water-rich asteroids are a proposed source of Earth’s water.
  • Delivery and retention are separate parts of the explanation.
  • Cooling allowed water vapour to condense.
  • The current exam evidence for this objective is limited.
ConceptIB Biology HL