| Clue | Source | Date |
|---|---|---|
| Methane produced in a swamp (2 wds.) | ||
| Methane variant (5-3) | ||
| Planet Mercury has less hot methane (5,3) | ||
| Methane, it's produced when vegetation decomposes in water (5-3) | ||
| Swampy emission making gash in planet (5,3) | ||
| Methane planet has -- breathing ultimately 'restricted'! | The Telegraph Cryptic | 08 Sep 2022 |
| Methane from bogs | The Times Concise | 27 Sep 2018 |
| Ignis fatuus source | ||
| Methane from a swamp |