If you are trying to get funding from NASA for a mission to another world to look
for life, saying you need money to look for something that we don't know if it
exists is a sure way not to get funding. That is the reality. You got to have some
idea of what you are looking for and it has to have some basis in reality - that
is why we sent the MERs to find signs of past water on Mars rather than some
other molecule.

What we have to hope for in your desire is serendipity - that while our probes
are out there exploring they come across something unexpected by chance.
That is how more than one paradigm-changing discovery has been made.