Sample return from a main-belt asteroid has not yet been attempted, but appears technologically feasible. While the cost implications are significant, the scientific case for such a mission appears overwhelming. As suggested by the “Grand Tack” model, the structure of the main belt was likely forged during the earliest stages of Solar System evolution in response to migration of the giant planets. Returning samples from the main belt has the potential to test such planet migration models and the related geochemical and isotopic concept of a bimodal Solar System. Isotopic studies demonstrate distinct compositional differences between samples believed to be derived from the outer Solar System (CC or carbonaceous chondrite group) and those that are thought to be derived from the inner Solar System (NC or non-carbonaceous group). These two groups are separated on relevant isotopic variation diagrams by a clear compositional gap. The interface between these two regions appears to be broadly coincident with the present location of the asteroid belt, which contains material derived from both groups. The Hayabusa mission to near-Earth asteroid (NEA) (25143) Itokawa has shown what can be learned from a sample-return mission to an asteroid, even with a very small amount of sample. One scenario for main-belt sample return involves a spacecraft launching a projectile that strikes an object and flying through the debris cloud, which would potentially allow multiple bodies to be sampled if a number of projectiles are used on different asteroids. Another scenario is the more traditional method of landing on an asteroid to obtain the sample. A significant range of main-belt asteroids are available as targets for a sample-return mission and such a mission would represent a first step in mineralogically and isotopically mapping the asteroid belt. We argue that a sample-return mission to the asteroid belt does not necessarily have to return material from both the NC and CC groups to viably test the bimodal Solar System paradigm, as material from the NC group is already abundantly available for study. Instead, there is overwhelming evidence that we have a very incomplete suite of CC-related samples. Based on our analysis, we advocate a dedicated sample-return mission to the dwarf planet (1) Ceres as the best means of further exploring inherent Solar System variation. Ceres is an ice-rich world that may be a displaced trans-Neptunian object. We almost certainly do not have any meteorites that closely resemble material that would be brought back from Ceres. The rich heritage of data acquired by the Dawn mission makes a sample-return mission from Ceres logistically feasible at a realistic cost. No other potential main-belt target is capable of providing as much insight into the early Solar System as Ceres. Such a mission should be given the highest priority by the international scientific community.

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通过来自主小行星带的样本返回探索双峰太阳系：重新审视谷神星的案例

尚未尝试从主带小行星返回样本，但在技术上似乎可行。虽然成本影响很大，但这种任务的科学案例似乎势不可挡。正如“Grand Tack”模型所暗示的那样，主带的结构很可能是在太阳系演化的最早阶段为响应巨行星的迁移而形成的。从主带返回的样本有可能测试此类行星迁移模型以及双峰太阳系的相关地球化学和同位素概念。同位素研究表明，被认为来自外太阳系（CC 或碳质球粒陨石群）的样本与被认为来自内太阳系（NC 或非碳质群）的样本之间存在明显的成分差异。这两组在相关的同位素变化图上被明显的成分差距分开。这两个区域之间的界面似乎与小行星带的当前位置大致一致，其中包含来自这两个群体的物质。Hayabusa 对近地小行星 (NEA) (25143) 的任务表明，即使样本量非常少，也可以从对小行星的样本返回任务中学到什么。主带样本返回的一个场景是航天器发射一个射弹，撞击物体并飞过碎片云，如果在不同的小行星上使用多个射弹，这可能允许对多个物体进行采样。另一种情况是更传统的登陆小行星获取样本的方法。大量主带小行星可作为样本返回任务的目标，这样的任务将代表小行星带矿物学和同位素测绘的第一步。我们认为，小行星带的样本返回任务不一定必须从 NC 和 CC 组返回材料才能有效地测试双峰太阳系范式，因为来自 NC 组的材料已经大量可用于研究。相反，有压倒性的证据表明我们有一套非常不完整的 CC 相关样本。根据我们的分析，我们主张对矮行星 (1) 谷神星进行专门的样本返回任务，作为进一步探索太阳系固有变异的最佳手段。谷神星是一个富含冰的世界，它可能是一个流离失所的海王星外天体。我们几乎可以肯定没有任何陨石与从谷神星带回的物质非常相似。黎明号任务获得的丰富数据遗产使得谷神星的样本返回任务在后勤上可行，成本切实可行。没有其他潜在的主带目标能够像谷神星那样深入了解早期太阳系。国际科学界应高度重视此类任务。