The finding by the OSIRIS‐REx (Origins, Spectral Interpretation, Resource Identification, and Security‐Regolith Explorer) mission that its target (101955) Bennu is an active asteroid has raised questions as to whether the observed particle ejection events are driven by temperature. To investigate sublimation of water ice and rock thermal fracture as possible temperature‐driven causes, we modeled the global temperatures of Bennu and searched for correlations with the identified ejection points on the asteroid surface. We computed temperatures with the Advanced Thermophysical Model and the 75‐cm‐resolution global shape model of Bennu derived by the OSIRIS‐REx mission. We find that ~1,856 m² of Bennu's polar regions have orbit‐averaged temperatures that are sufficiently cold to enable water ice, if buried within the top few meters of the surface, to remain stable over geological timescales. Millimeter thick layers of surface water ice are also stable over ~10³‐year timescales within polar centimeter‐scale cold traps. However, we do not find evidence of conditions enabling ice stability in the warmer equatorial regions, where ejection events have been observed, implying that sublimation of water ice is not the cause of particle ejection. Conversely, rock thermal fracture remains a possible mechanism of particle ejection. We find high amplitudes of diurnal temperature variation, a proxy for the efficacy of thermal fracturing, at all latitudes on Bennu due to its extreme ruggedness. Therefore, if rock thermal fracture is the mechanism, particles could be ejected from any latitude, which is consistent with the continued observations of particle ejection by OSIRIS‐REx.

中文翻译：

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小行星的高分辨率温度模拟对冰稳定性和颗粒喷射的影响（101955）Bennu

OSIRIS-REx（起源，光谱解释，资源识别和安全性-雷戈利斯探索者）任务发现其目标（101955）Bennu是一颗活跃的小行星，这引起了人们对观察到的粒子喷射事件是否受温度驱动的质疑。为了研究水冰和岩石热破裂的升华是可能的温度驱动原因，我们对Bennu的全球温度进行了建模，并搜索了与小行星表面上确定的喷射点的相关性。我们使用OSIRIS-REx任务导出的高级热物理模型和Bennu的75厘米分辨率全球形状模型计算了温度。我们发现〜1,856 m ²Bennu的极地地区的轨道平均温度足够冷，以使水冰（如果掩埋在地表的顶部几米之内）可以在地质时标上保持稳定。毫米厚的地表水冰层在约10 ³内也稳定极厘米级冷阱内的年时间尺度。但是，我们没有找到证据证明在较暖的赤道地区能够使冰稳定的条件，在这些较暖的赤道地区已经观测到喷射事件，这意味着水冰的升华不是粒子喷射的原因。相反，岩石热破裂仍然是颗粒喷射的可能机制。由于Bennu的极端坚固性，我们在Bennu的所有纬度上都发现了昼夜温度变化的高幅度，这是热压裂效果的代表。因此，如果是岩石热破裂的机理，则颗粒可以从任何纬度喷出，这与OSIRIS-REx对颗粒喷出的持续观察一致。