Lapôtre Mathieu G A, Malaska Michael J, Cable Morgan L
Department of Gelogical Sciences Stanford University Stanford CA USA.
Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA.
Geophys Res Lett. 2022 Apr 28;49(8):e2021GL097605. doi: 10.1029/2021GL097605. Epub 2022 Apr 25.
Titan is a sedimentary world, with lakes, rivers, canyons, fans, dissected plateaux, and sand dunes. Sediments on Saturn's moon are thought to largely consist of mechanically weak organic grains, prone to rapid abrasion into dust. Yet, Titan's equatorial dunes have likely been active for 10s-100s kyr. Sustaining Titan's dunes over geologic timescales requires a mechanism that produces sand-sized particles at equatorial latitudes. We explore the hypothesis that a combination of abrasion, when grains are transported by winds or methane rivers, and sintering, when they are at rest, could produce sand grains that maintain an equilibrium size. Our model demonstrates that seasonal sediment transport may produce sand under Titan's surface conditions and could explain the latitudinal zonation of Titan's landscapes. Our findings support the hypothesis of global, source-to-sink sedimentary pathways on Titan, driven by seasons, and mediated by episodic abrasion and sintering of organic sand by rivers and winds.
土卫六是一个沉积世界，有湖泊、河流、峡谷、冲积扇、切割高原和沙丘。土星卫星上的沉积物被认为主要由机械强度较弱的有机颗粒组成，容易迅速磨蚀成尘埃。然而，土卫六赤道地区的沙丘可能已经活跃了数十至数百千年。在地质时间尺度上维持土卫六的沙丘需要一种在赤道纬度产生沙粒大小颗粒的机制。我们探讨了这样一种假设：当颗粒被风或甲烷河流搬运时发生的磨蚀，以及当它们静止时发生的烧结，两者相结合可以产生保持平衡大小的沙粒。我们的模型表明，季节性沉积物搬运在土卫六的表面条件下可能产生沙子，并可以解释土卫六地貌的纬度分带。我们的研究结果支持了土卫六上由季节驱动、由河流和风对有机沙的间歇性磨蚀和烧结介导的全球源到汇沉积路径的假设。
