What Mars Fossils Might Look Like

[mickw]

Fossil microbes found along an iron-rich river in Spain reveal how signs of life could be preserved in minerals found on Mars. The discovery may help to equip the next generation Mars rover with the tools it would need to find evidence of past life on the planet.
The Rio Tinto arises from springs west of Seville. These springs percolate up through iron ores that were deposited by geothermal activity more than 200 million years ago. Spring water dissolves iron sulfide minerals from the ores, and this stains the river red. The iron sulfide minerals also dissociate to form sulfuric acid.

More:  http://www.space.com/scienceastronomy/080501-am-mars-life-iron.html