Recent replenishment of aliphatic organics on Ceres from a large subsurface reservoir

Ceres hosts significant aliphatic-organic concentrations, ranging from approximately 5 wt.% to >30 wt.% in specific surface areas. The origins and persistence of these organics are under debate due to the intense aliphatic signature and radiation levels in Ceres' orbit, which would typically lead to their destruction, hindering detection. To investigate this, we conducted laboratory experiments to replicate how the signature of the organic-rich regions would degrade due to radiation. Our findings indicate a fast degradation rate, implying the exposure of buried organics within the last few million years. This degradation rate, coupled with observed quantities, implies that the aliphatics must be present in substantial quantities within the shallow subsurface. Our estimates suggest an initial aliphatic abundance 2-30 times greater than currently observed, surpassing significantly the levels found in carbonaceous chondrites, indicating either a significant concentration or remarkable purity.

谷神星（Ceres）拥有可观的脂肪族有机物含量，在特定表面区域内，其含量约为5重量百分比（wt.%）至30重量百分比以上。鉴于谷神星轨道区域存在高强度辐射与强烈的脂肪族特征信号，这类有机物的起源与存续性一直存在争议——此类辐射通常会破坏有机物，进而阻碍其被探测到。为探究这一问题，我们开展了实验室模拟实验，以复现富含有机物区域的特征信号如何因辐射作用发生降解。我们的研究结果显示降解速率极快，这表明埋藏的有机物是在数百万年内才被暴露出来的。结合观测到的有机物含量与该降解速率，可以推断，浅表层地下环境中必然存在大量脂肪族有机物。我们的估算显示，初始脂肪族有机物丰度是当前观测值的2至30倍，显著高于碳质球粒陨石（carbonaceous chondrites）中的有机物含量水平，这表明要么有机物经历了显著富集，要么其纯度极高。