Parent bodies of C-type asteroids may have brought key volatile and organic-rich compounds to the terrestrial planets in the early stages of the Solar System. At the end of 2020, the JAXA Hayabusa2 mission successfully returned samples from Ryugu, providing access to a primitive matter that has not suffered terrestrial alteration. Here we report the discovery of a peculiar class of grains, up to a few hundreds of micrometres in size, that have a hydrated ammonium–magnesium–phosphorus (HAMP)-rich composition. Their specific chemical and physical properties point towards an origin in the outer Solar System, beyond most snow lines, and their preservation along Ryugu history. These phosphorus-rich grains, embedded within an organic-rich phyllosilicate matrix, may have played a major role when immersed in primitive terrestrial water reservoirs. In particular, in contrast to poorly soluble calcium-rich phosphates, HAMP grains favour the release of phosphorus-rich and nitrogen-rich ionic species, to enter chemical reactions. HAMP grains may have thus critically contributed to the reaction pathways of organic matter towards a biochemical evolution.

C型小行星的母体可能为太阳系早期的类地行星带来了关键的挥发性和富含有机物的化合物。 2020 年底，JAXA 隼鸟 2 号任务成功从龙宫带回了样本，为了解尚未遭受地球改造的原始物质提供了机会。在此，我们报告了一种特殊颗粒的发现，其尺寸可达数百微米，其成分富含水合铵镁磷 (HAMP)。它们特定的化学和物理特性表明它们起源于大多数雪线之外的太阳系外层，并且它们在龙宫历史上得到了保存。这些富含磷的颗粒嵌入富含有机物的层状硅酸盐基质中，当浸入原始陆地水库时可能发挥了重要作用。特别是，与难溶性的富钙磷酸盐相比，HAMP 颗粒有利于释放富磷和富氮离子物质，以进入化学反应。因此，HAMP 颗粒可能对有机物向生化进化的反应途径做出了至关重要的贡献。