Abundances and the partitioning between ices and gases in gas–grain chemistry are governed by adsorption and desorption on grains. Understanding of astrophysical observations relies on laboratory measurements of adsorption and desorption rates on dust grains analogues. On flat surfaces, gas adsorption probabilities (or sticking coefficients) have been found to be close to unity for most gases^1,2,3. Here we report a strong decrease in the sticking coefficients of H₂O and CO₂ on substrates more akin to cosmic dust, such as submicrometre-sized particles of carbon and olivine, bare or covered with ice. This effect results from the local curvature of the grains, and then extends to larger grains made of aggregated small particles, such as fluffy or porous dust in more evolved media (for example, circumstellar disks). The main astrophysical implication is that accretion rates of gases are reduced accordingly, slowing the growth of cosmic ices. Furthermore, volatile species that are not adsorbed on a grain at their freeze-out temperature will persist in the gas phase, which will impact gas–ice partitions. We also found that thermal desorption of H₂O is not modified by grain size, and thus the temperature of snowlines should be independent of the dust size distribution.

气体-颗粒化学中冰和气体之间的丰度和分配受颗粒上的吸附和解吸控制。对天体物理观测的理解依赖于对尘粒类似物吸附和解吸速率的实验室测量。^{在平坦表面上，已发现大多数气体1,2,3}的气体吸附概率（或粘附系数）接近统一。_{在这里，我们报告了 H 2} O 和 CO ₂的粘附系数显着下降在更类似于宇宙尘埃的基底上，例如亚微米大小的碳和橄榄石颗粒，裸露或覆盖着冰。这种效应是由颗粒的局部曲率引起的，然后延伸到由聚集的小颗粒组成的较大颗粒，例如更进化的介质（例如，环星盘）中的蓬松或多孔尘埃。主要的天体物理学影响是气体的吸积率相应降低，减缓了宇宙冰的生长。此外，在冻结温度下未吸附在谷物上的挥发性物质将在气相中持续存在，这将影响气冰分区。我们还发现 H ₂ O 的热解吸不受颗粒尺寸的影响，因此雪线的温度应该与粉尘尺寸分布无关。