There are a number of reports of salt deposits found on mars. While salt does not necessarily = life it does show where large bodies of water may have
been and water 'usually' equals life.

March 20, 2008 -- Scientists have discovered salt deposits on the surface of Mars, indicating that water was once plenty and pointing to sites
that could provide evidence of past life, a study said Thursday.
link to story
Here is another related story suggesting liquid water might still be found on Mars.
Is the Signature Still Wet?
Every day we are getting closer to finding lief on Mars. Or have they already found it and we are just being drip fed the facts?