NASA scientists propose new 'alien life evidence' scale

 As the search for extraterrestrial life heats up, scientists may need to step up their reporting game a bit.
Researchers should report evidence for alien life on a scale similar to the technological readiness level scale commonly used to assess the readiness of spaceflight components, a new paper argues. The goal is to make the search for life less "binary" — life or no life — and to express it more accurately in terms of agreed-upon scientific uncertainty.
The newly proposed alien-life evidence scale was outlined in a study published online Oct. 27 in the journal Nature that was led by NASA chief scientist Jim Green. The scale includes seven levels, which are subject to change depending on the type of environment involved and how the scientific community responds. 

For a Mars mission, for example, finding hints of a signature of life would register at Level 1 on the scale, and showing that the discovery was not due to contamination by Earth life would raise it to Level 2. The highest levels include verifying signs of life with several instruments (Level 6) and in different locations on a world (Level 7).