What is the key non-living component scientists have found on Mars
that suggest the possibility of life there?

Gina8912 --

As early as 2000, scientists were finding increasing evidence of water
on Mars, an indication that microbial life might exist:

Space.com
"NASA announces discovery of evidence of water on Mars" (June 25, 2000)
http://www.space.com/scienceastronomy/solarsystem/mars_water_000620.html

These findings have been supported by evidence found by the Mars Rover:

NASA/JPL
"Opportunity Rover Finds Strong Evidence Meridiani Planum Was Wet," (March 2, 2004)
http://marsrovers.jpl.nasa.gov/newsroom/pressreleases/20040302a.html

Google search strategy:
Mars "evidence of water"

Best regards,

Omnivorous-GA