The Scientific Importance of Returning Airfall Dust as a Part of Mars Sample Return (MSR)

Dust transported in the martian atmosphere is of intrinsic scientific interest as well as having relevance for the planning of human missions in the future. The MSR Campaign, as presently designed, presents an important opportunity to return serendipitous, airfall dust. The tubes containing samples collected by the Perseverance rover would be placed in cache depots on the martian surface perhaps as early as 2023-24 for recovery by a subsequent mission no earlier than 2028-29, and possibly as late as 2030-31. Thus, the sample tube surfaces could passively collect dust for multiple years. This dust is deemed to be exceptionally valuable as it would inform our knowledge and understanding of Mars’s global mineralogy, surface processes, surface-atmosphere interactions, and atmospheric circulation. Preliminary calculations suggest that the total mass of such dust on a full set of tubes could be as much as 100 mg and, therefore, sufficient for many types of laboratory analyses. Two planning steps would optimize our ability to take advantage of this opportunity: 1) the dust-covered sample tubes should be loaded into the Orbiting Sample container (OS) with minimal cleaning, and 2) the capability to recover this dust early in the workflow within the SRF needs to be established. A further opportunity to advance dust/atmospheric science using MSR, depending upon the design of the MSR Campaign elements, may lie with direct sampling and the return of airborne dust.

火星大气中输送的尘埃既具有内在的科学研究价值，也与未来载人火星任务的规划息息相关。按当前方案设计的火星样本返回（Mars Sample Return, MSR）任务计划，为偶然收集并返回降落尘埃提供了重要契机。由毅力号（Perseverance）火星车采集的样本管，最早可能于2023至2024年间被放置在火星表面的缓存库中，待后续任务最早于2028至2029年、最晚至2030至2031年期间完成回收。因此，样本管表面可在多年间被动收集尘埃。此类尘埃被认为具有极高的科研价值，因为它将为我们认知火星全球矿物学、表面过程、地表-大气相互作用及大气环流提供关键支撑。初步计算表明，一套完整样本管上附着的尘埃总质量可达100毫克，足以支撑多种实验室分析工作。有两项规划步骤可优化我们利用该契机的能力：其一，附着尘埃的样本管应仅经过最低限度的清洁后装入轨道样本容器（Orbiting Sample Container, OS）；其二，需在样本返回设施（Sample Return Facility, SRF）的工作流程早期建立回收此类尘埃的能力。此外，根据MSR任务计划各环节的设计方案，借助该任务开展尘埃/大气科学研究的另一契机，或在于直接采样并返回大气尘埃。