From extreme terrestrial analogues to returned samples: Implications of organic carbon evolution for China’s Tianwen-2 and Tianwen-3 missions

China’s upcoming deep-space sample return missions, Tianwen-2 and Tianwen-3, will provide unprecedented opportunities to investigate the origin, evolution and preservation of organic matter beyond Earth. A critical challenge for these missions is not only the detection of organics, but also the interpretation of their molecular signatures under complex thermal and geological histories. Here we present how recent advances in molecular-scale characterization of organic carbon in extreme terrestrial and extraterrestrial analogues can inform scientific strategies for these future missions.

We integrate results from three complementary research directions: (1) abyssal hydrothermal systems on Earth, (2) Martian meteorite Tissint, and (3) terrestrial hot-spring sinters as Mars analogues. Using metabolomics-inspired molecular networking , we show that hydrothermal alteration drives a systematic molecular evolution from simple reduced carbon to increasingly functionalized, heteroatom-rich compounds. Stepwise pyrolysis GC–MS and algorithmic spectral deconvolution applied to the Tissint meteorite reveal strong thermal–spatial heterogeneity of indigenous insoluble organic matter, indicating high-temperature synthesis linked to impact-related hydrothermalism and magmatism on Mars. Parallel studies of siliceous hot spring sinters further demonstrate how distance from hydrothermal centers controls the preservation state of recalcitrant organic molecules under Mars-like extreme conditions.

Together, these findings provide a framework for interpreting organic signals in returned samples: (i) distinguishing indigenous organics from contamination through molecular-network fingerprints, (ii) reconstructing thermal histories using molecular structural distributions, and (iii) identifying sampling contexts most favorable for preserving primitive or prebiotic compounds. These insights are directly relevant to the scientific planning of Tianwen-2 asteroid samples and the forthcoming Tianwen-3 Mars sample return mission, particularly for strategies targeting life-marker detection, sample triage, and laboratory analytical protocols after return.

Our work demonstrates how Earth-based extreme analogues and meteorite studies can serve as a methodological and conceptual bridge between current remote/in-situ observations and the next era of Chinese deep-space sample science.