The discovery of fossils in gypsum on Earth may help scientists zero in on fossils containing past life on Mars.
Scientists find microfossils in gypsum formed when the Mediterranean Sea dried up six million years ago.
Scientists didn't know the soft mineral could preserve microscopic fossils of ancient life.
The discovery raises the prospect that Mars' rich deposits of gypsum may hold fossil records as well.
A common mineral widely believed to be a poor vessel for fossils actually contains a treasure trove of ancient life, a discovery that may lead scientists searching for life on Mars to the planet's sweet spot.
Both Earth and Mars have the mineral gypsum, though it hasn't been of much interest to scientists studying ancient life forms because no one believed tiny fossils could last in the soft, water-soluble mineral, also known as calcium sulfate.
But scientists at an astrobiology conference in Houston will report today that microscopic remnants of a diverse collection of algae and phytoplanktons have been found in samples of gypsum that formed six million years ago when the Mediterranean Sea went dry.