There's an interesting paper in "Astrobiology" (Volume 15, Number 2, 2015) entitled:
"Ancient Sedimentary Structures in the <3.7 Ga Gillespie Lake Member, Mars, That Resemble Macroscopic Morphology, Spatial Associations, and Temporal Succession in Terrestrial Microbialites"
http://online.liebertpub.com/doi/pdf.../ast.2014.1218
The author Nora Noffke hasn't actually claimed that she has found compelling evidence for life on Mars. She has published a "Hypothesis Article" , and provides a hypothesis (NOT a claim!) that:
"The sedimentary structures in the <3.7 Ga Gillespie Lake Member on Mars are ancient microbially induced sedimentary structures (MISS) produced by interactions between microbial mats and their environment"
She goes on to spell out what further detailed investigations this would prompt to test the hypotheses; specifically, she gives "a strategy for detecting, identifying, confirming, and differentiating possible MISS during current and future Mars missions."
It seems like an entirely reasonable and scientific paper to me, which will no doubt be examined and tested by others in accordance with "The Scientific Method".