https://motherboard.vice.com/en_us/article/mb4g8b/signs-of-alien-life-on-europa-might-only-be-centimeters-under-the-surface

Miles below the icy surface of Jupiter’s moon Europa, there is an ocean that likely contains more water than all the seas on Earth. This intriguing marine environment has distinguished Europa as one of the most promising candidates to host alien life in the solar system.

But there’s a catch: The moon is blasted by Jupiter’s intense radiation, so any biological material exposed on its surface would be damaged, perhaps beyond recognition. That presents an obvious challenge for future lander missions seeking signs of life in Europa’s outer crust.