What signs of life are scientists looking for on Mars?
The smells of digestion. Life, as we know it, depends on chemicals built up from carbon and nitrogen, and whenever those chemicals break down they release gases like methane (CH4) and ammonia (NH3). To read this story in full you will need to login or make a payment (see right). Comments Reader comments are usually moderated after posting. If you find something offensive or inappropriate, you can speed this process by clicking ‘Report this comment’ (or, if that doesn’t work for you, email webadmin@nature.com). For more controversial topics, we reserve the right to moderate before comments are published. There are currently no comments.
