https://www.vice.com/en_us/article/88a3ka/earth-microbes-can-survive-on-the-surface-of-mars-study-suggests

Last week, NASA landed its Perseverance rover on Mars, kicking off a new mission that will hunt for signs of microbial life that might have thrived in the wetter, warmer conditions on the red planet billions of years ago. Finding tiny Martian fossils would be one of the most spectacular breakthroughs in history. But what about the odds that life could exist on Mars right now?

Answering this question is important not only for understanding modern Mars, but also to mitigate the risk that microbes from Earth are accidentally deposited by spacecraft on this pristine planet, a process known as forward contamination.