A meteorite that fell to Earth from Mars purported to offer evidence of past Martian biology has fallen from grace. That’s the assertion from two scientists who say the rock’s strongest link to life — as claimed by other researchers — has broken down. In December 1984, ALH 84001 — often called the “Mars rock” — was picked up in Antarctica by a National Science Foundation-sponsored meteorite-hunting expedition. Tossed into space by an asteroid or comet that hit Mars billions of years past, the tiny piece of rock eventually found its way to Earth. It is believed to have landed in Antarctica some 13,000 years ago. In August 1996, a science team led by NASA Johnson Space Center experts declared that they had uncovered evidence inside ALH 84001 for Martian biological activity. Ultra-small and segmented, rod-shaped structures were read by the team as the fossil leftovers of Martian microbial life. Since that time, the diminutive four and three-quarter pounds (1.93 kilograms) of potato-shaped Mars rock has weighed heavy on minds of scientists around the world.