Across
- 3. Equation for estimating extraterrestrial civilizations.
- 7. Building block of proteins.
- 9. Hypothesis life spreads across space.
- 10. Early Earth organisms that produced oxygen.
- 15. Paradox about missing extraterrestrial life.
- 16. Planet outside our solar system.
Down
- 1. The "Red Planet," often a target for life search.
- 2. Gas that could signal microbial life.
- 4. Moon of Jupiter, possibly harboring life beneath its ice.
- 5. Essential for life as we know it.
- 6. Evidence of past or present life.
- 8. Conditions suitable for life.
- 11. Layer of microorganisms adhering to surfaces.
- 12. Molecule critical for life, may predate DNA.
- 13. Single-celled organism, often used in life research.
- 14. Saturn's moon with possible subsurface oceans.