In the next decade, a space mission will scoop up samples from Mars and bring them to Earth. We don't want life to contaminate our planet, so scientists have developed a technique to scan the samples for evidence of microbial life. While conventional instruments couldn't detect life in samples of 100 million-year-old basaltic rock, they shined infrared light on thin slices of rock and detected microbes. Next, they need to push the technique to 2 billion-year-old samples.

https://www.u-tokyo.ac.jp/focus/en/press/z0508_00392.html