From ScienceDaily: Yes, NASA is shaking the can again but never mind.
Iron-rich rocks near ancient lake sites on Mars could hold vital clues that show life once existed there, research suggests.
These rocks — which formed in lake beds — are the best place to seek fossil evidence of life from billions of years ago, researchers say.
A new study that sheds light on where fossils might be preserved could aid the search for traces of tiny creatures — known as microbes — on Mars, which it is thought may have supported primitive life forms around four billion years ago.
A team of scientists has determined that sedimentary rocks made of compacted mud or clay are the most likely to contain fossils. These rocks are rich in iron and a mineral called silica, which helps preserve fossils.
They formed during the Noachian and Hesperian Periods of Martian history between three and four billion years ago. At that time, the planet’s surface was abundant in water, which could have supported life.
The rocks are much better preserved than those of the same age on Earth, researchers say. This is because Mars is not subject to plate tectonics — the movement of huge rocky slabs that form the crust of some planets — which over time can destroy rocks and fossils inside them.
The team reviewed studies of fossils on Earth and assessed the results of lab experiments replicating Martian conditions to identify the most promising sites on the planet to explore for traces of ancient life. Paper. (open access) – S. McMahon, T. Bosak, J. P. Grotzinger, R. E. Milliken, R. E. Summons, M. Daye, S. A. Newman, A. Fraeman, K. H. Williford, D. E. G. Briggs. A Field Guide to Finding Fossils on Mars. Journal of Geophysical Research: Planets, 2018; DOI: 10.1029/2017JE005478 More.
Paper (pdf).
In short, they haven’t really found anything except a promising place to look, but that is a start.
There are those who believe that we have in fact discovered life on Mars during previous missions (see links below). Answers will likely only come from a manned mission. There is only so much one can do from a desk.
By the way, don’t expect a big religious crisis to follow such a discovery, as some grantseekers have claimed. Rather, people who haven’t taken panspermia (maybe life came from outer space) seriously will need to rethink the matter.
See also: Did Viking discover life on Mars forty years ago?
Ethan Siegel at Forbes: Was life found on Mars 40 years ago?
Panspermia (maybe life came from outer space) is back, in Progress in Biophysics and Molecular Biology
and
Don’t let Mars fool you. Those exoplanets teem with life!