Why are sensors used to find organic chemicals and organic waste on other planets?

Question

full question: sensors that have searched for life on the moon and on plantets other then earth have been programmed to look for organic chemicals and organic waste products, such as methane. explain why these types of sensors are used.

please answer.. good answere will get points

Answer 1

I think the question is pretty self explanatory.  They use those sensor to detect methane which is a common chemical produced by waste from most life forms, especially the oldest from of life on Earth, bacteria.  If they can find these compounds on the moon, since the atmosphere of the moon does not naturally contain methane, it would prove some kind of life from had to be present to create the methane.