Data collected 25 years ago on the surface of Mars by NASA’s twin Viking landers show evidence of life, a scientist claimed Friday. Other scientists quickly cast doubt on the claim by Joseph Miller. They cited a variety of other explanations for the data radioed back to Earth as the landers performed experiments in an effort to find any trace of life on the Red Planet. Miller, an associate professor in the Department of Cell and Neurobiology at the University of Southern California in Los Angeles, said he detected distinct rhythms in the levels of gas given off during the range of experiments that sought to prompt the growth of microbial life in samples of Martian soil doused with water and nutrients.