ExplainedA solid ordinary explanation fits the evidence.
The claim
"Tiny worm-like shapes in a Martian meteorite are fossil bacteria."
Where the idea comes from
A NASA team led by David McKay announced possible microfossils in Science in August 1996; President Clinton made a statement.
What the evidence shows
- The team cited four lines of evidence: carbonate globules, magnetite crystals, organic molecules and worm-like shapes.
- The shapes are 20 to 100 nanometres long, smaller than any known cell on Earth.
- Each line of evidence was later shown to form without life, and some organics turned out to be Antarctic contamination.
- A 2022 study in Science found its organic molecules formed when water reacted with the rock (serpentinisation), not from life.
What is still open
It remains a valuable sample of early Mars, and part of why NASA wanted samples returned.
Our verdict
Explained Chemistry, not fossils.
Sources
Checked 31 October 2026. Spotted a newer source? Tell us.
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