Traces of what looked like a green clay mineral.

看上去像是某种绿色粘土矿物的痕迹。

At the bottom of ancient rivers, now dry and lifeless, scientists have discovered clay minerals buried in the soil.

在如今干涸且毫无生气的古老河流底部，科学家们发现了埋藏在土壤中的粘土矿物。