Life on Mars

What the rover actually measured

The mudstone holds organic carbon, sulfur, oxidized iron, and phosphorus. Millimeter-scale spots, called leopard spots, and smaller flecks go with iron phosphate and iron sulfide minerals, consistent with vivianite and greigite. On Earth those minerals often form where microbes process mud, and they can also form without life. The team argues the textures fit cool, wet chemistry after the mud was laid down, not a later blast of heat. ^[1]

NASA's acting administrator at the time called it the closest the agency had come to discovering life on Mars. The same release says abiotic explanations are less likely given the paper, and that they cannot be ruled out. Both sentences belong in the record. ^[1]

Older hints, still short of proof

The Viking landers in 1976 ran biology tests. One of them, the labeled-release experiment, gave a result some researchers still defend. The wider judgment is that the tests did not show life, and that the soil chemistry is harsh, with Perchlorates that break organic molecules apart. Curiosity has since detected organic molecules in Gale and has reported methane that comes and goes. Methane can be made by life or by rock. A varying trace gas is not an organism.

Meteorites from Mars, found on Earth, have prompted the same argument. None of them is accepted as a fossil.

Why the sample is still there

The way to test Sapphire Canyon properly is in laboratories on Earth. That was the point of Mars Sample Return. Science reported on 5 August 2026 that the spending agreement does not support the existing program. The tube remains with the cache on Mars, alongside the Three Forks depot described on Jezero crater and Exploration of Mars. ^{[1] [2]}