The search for biosignatures is likely to generate controversial results, with no single biosignature being clear proof of the presence of life. Bayesian statistical frameworks have been suggested as a tool for testing the effect that a new observation has on our belief in the presence of life on another planet. We test this approach here using the tentative discovery of phosphine on Venus as an example of a possible detection of a biosignature on an otherwise well-characterized planet. We report on a survey of astrobiologists' views on the likelihood of life on Enceladus, Europa, Mars, Titan and Venus before the announcement of the detection of phosphine in Venus' atmosphere (the Bayesian Prior Probability) and after the announcement (the Posterior Probability). Survey results show that respondents have a general view on the likelihood of life on any world, independent of the relative ranking of specific bodies, and that there is a distinct ‘fans of icy moons’ sub-community. The announcement of the potential presence of phosphine on Venus resulted in the community showing a small but significant increase in its confidence that there was life on Venus; nevertheless the community still considers Venus to be the least likely abode of life among the five targets considered, last after Titan. We derive a Bayesian formulation that explicitly includes both the uncertainty in the interpretation of the signal as well as uncertainty in whether phosphine on Venus could have been produced by life. We show that although the community has shown rational restraint about a highly unexpected and still tentative detection, their changing expectations do not fit a Bayesian model.

中文翻译：

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天体生物学家是理性的，但不是贝叶斯的

寻找生物印记可能会产生有争议的结果，没有单一的生物印记可以明确证明生命的存在。贝叶斯统计框架已被建议作为一种工具，用于测试新观察对我们对另一个星球上存在生命的信念的影响。我们在这里测试这种方法，使用金星上磷化氢的初步发现作为可能在其他特征良好的行星上检测到生物印记的例子。我们报告了一项关于天体生物学家对土卫二、欧罗巴、火星、土卫六和金星生命可能性的看法的调查，该调查在宣布在金星大气中检测到磷化氢之前（贝叶斯先验概率）和宣布之后（后验概率） ）。调查结果表明，受访者对任何世界上存在生命的可能性都有一般看法，与特定天体的相对排名无关，并且存在明显的“冰月爱好者”子社区。金星上可能存在磷化氢的宣布导致社区对金星上存在生命的信心小幅但显着增加；尽管如此，社区仍然认为金星是所考虑的五个目标中最不可能的生命栖息地，仅次于泰坦。我们推导出一个贝叶斯公式，该公式明确包括信号解释的不确定性以及金星上的磷化氢是否可能由生命产生的不确定性。我们表明，尽管社区对高度出乎意料且仍处于试探性的检测表现出理性克制，