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Xiaoou Luo

Publications and source records attributed to Xiaoou Luo.

2 recordsLinked to original sources
arXiv2026

Influence of CO versus CH$_4$ on organic haze formation in atmospheres of diverse terrestrial exoplanets

Context. Terrestrial exoplanets are expected to host secondary, high-metallicity atmospheres derived from outgassing of volatiles such as N2, CO2, H2O, CH4, and CO. Photochemical organic hazes are likely to form in such environments, significantly affecting atmospheric observations and planetary habitability. Aims. We investigate haze formation in representative terrestrial exoplanet atmospheres and assess how CH4 versus CO as the primary carbon source affects haze production rates, particle properties, and chemical complexity. Methods. We performed six laboratory simulations by exposing gas mixtures at a few mbar to glow discharge at 300 K. Each atmosphere contained 75% N2, CO2, or H2O, 10% of each of the other two gases, and 5% CH4 or CO. Gas-phase products were analyzed with a residual gas analyzer, and solid products were characterized by production rate, particle density, atomic force microscopy, Fourier-transform infrared spectroscopy, and very high-resolution mass spectrometry. Results. CH4 experiments produced more diverse gas-phase species and much higher haze yields than the corresponding CO experiments. CO-derived hazes showed a narrow particle size range of 10-80 nm, whereas CH4-derived hazes were denser and chemically more complex. The identified molecular formulas suggest growth pathways linked to gaseous precursors such as HCN, CH2O, and C2H4. Conclusions. The atmospheric redox state critically controls haze formation in simulated terrestrial exoplanet atmospheres. CH4 is significantly more effective than CO in initiating organic growth, leading to higher haze production rates and greater chemical complexity. These results provide useful constraints for exoplanet atmospheric modeling and spectral interpretation, and further support the possibility that reducing atmospheres may facilitate prebiotic organic chemistry relevant to the emergence of life.

astro-ph.EP↗
arXiv2026

Quantifying Building Blocks of Life in Planetary Analog Materials: Implications for Prebiotic Chemistry and Biosignature Identification

Building blocks of life such as amino acids, nucleobases, and fatty acids are central to prebiotic chemistry and represent key targets in the search for planetary biosignatures. In planetary materials, biomolecules typically occur at trace levels within complex matrices, posing substantial analytical challenges, particularly for quantitative characterization. Here we develop a gas chromatography tandem mass spectrometry method that enables robust qualitative and quantitative analysis of 56 prebiotically relevant molecules. The method is applied to a Titan aerosol analog and, for the first time, to a Martian gypsum analog from the Qaidam Basin, revealing diverse inventories of amino acids, nucleobases, and fatty acids in both samples. In the Titan aerosol analog, the first detection of phenylalanine and an extensive inventory of fatty acids, together with elevated nucleobase abundances, offers new insights into atmospheric photochemical synthesis of prebiotic molecules. In the Martian analog sample, amino acids are detectable and exhibit pronounced biotic abiotic contrasts in abundance patterns relative to those observed in the Titan aerosol analog, whereas fatty acids show more overlapping abiotic and biotic signatures, highlighting the potential of amino acids as robust biosignatures. These results provide quantitative constraints on prebiotic chemical evolution and underscore the utility of GC-MS-MS for biosignature identification in planetary exploration.

astro-ph.EP↗