A trained dog can detect a single drop of blood diluted in 20 Olympic-sized swimming pools — a sensitivity so extreme that dogs can pick up the molecular traces of cancer in a person's breath — and a 2024 study found them correctly identifying breast, lung, prostate, and colorectal cancer with roughly 94 percent accuracy

A trained dog can detect a single drop of blood diluted in 20 Olympic-sized swimming pools — a sensitivity so extreme that dogs can pick up the molecular traces of cancer in a person's breath — and a 2024 study found them correctly identifying breast, lung, prostate, and colorectal cancer with roughly 94 percent accuracy

Somewhere in a quiet research facility outside Tel Aviv, a Labrador retriever named Mars is being asked to do something a $100,000 mass-spectrometry machine cannot reliably do in twenty minutes: identify whether the person who recently breathed into a surgical mask has cancer. Mars sniffs the mask, considers the result for a moment, and either sits down — his signal for cancer — or moves to the next sample. He gets it right about 94 percent of t…