The only convincing evidence for life on Mars will be when we have a microbe in the lab from a sample return mission.

火星上存在生命的唯一可信依据将会是我们实验室里有从返回任务带回的样本中提取的微生物。

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"It has so much capability, so much more capability than any other vehicle, that I think we can start to contemplate missions like a Mars sample return, which requires a tremendous amount of lift capability because you've got to send a lander to Mars that still has enough propellant to return to Earth."

VOA: special.2011.04.11

DiGregorio, who founded the International Committee Against Mars Sample Return, will present his new report later this month at an astrobiology conference in San Diego sponsored by the International Society for Optical Engineers.

CNN: Researcher: Mars rock varnish hints of life