In just over a decade, samples of Martian soil scooped up by the Mars Perseverance rover are set to return to Earth after being retrieved by the first humans to set foot on Mars.

While scientists are excited to see what scientific discoveries await, they may have to temper their expectations. That's because acidic fluids — which once flowed on the surface of the red planet — may have destroyed biological evidence hidden within Mars' iron-rich clays.

A new paper, by researchers at Cornell University and at Spain's Centro de Astrobiología, details how they came to this conclusion.