In August, scientists announced they had discovered a whole lot of water on Mars, with enough sub-surface water to potentially cover the planet in a one-mile-deep ocean.
When it comes to finding life on an exoplanet many light-years away, it's becoming clear that we astrobiologists need to think deeply about life's planet context.
Biosignatures will be evidence of biospheres, showing how the sum of life on an alien world has changed that world in detectable ways.
There is always the possibility that some 'abiotic' process might also produce the signature we're looking for, which astrobiologists refer to as a 'false positive.'
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