研究人员在海底热泉附近发现了可能是古代微生物留下的生物特征。

Researchers discovered potential ___bio-signatures near hydrothermal vents that may indicate ancient microbial life.

科学家在火星土壤中发现了可能暗示过去存在生命的生物标记。

Scientists found a potential ___bio-signature in Martian soil that may suggest past life.