报告地点: 教学行政楼706会议室
报告时间:
2019-01-11
从 10:00 到 11:00
报告人: 秦川 博士
报告人简介:
秦川博士于2008年获得中国科学技术大学物理学本科学位，随后就读于美国科罗拉多大学攻读博士，并于2015年获得物理学博士学位，目前在哈佛大学地球与行星科学系从事博士后工作。博士期间，秦川跟随钟时杰老师对月球在不同时间尺度下的动力学过程进行了深入研究，成果包括发明了一套利用月球在潮汐力作用下的响应来约束深部长波结构的理论方法，及对月球化石隆起的成因给出了清晰的动力学解释。博士后期间，秦川尝试利用GPS观测的地表潮汐形变来约束深部地幔的弹性和密度结构。
报告题目: Formation of Moon's fossil bulge and its implication for Earth's early conditions
报告内容简介:
First recognized by Laplace over two centuries ago, the lunar gravitational anomalies associated with tidal-rotational bulges are significantly larger than hydrostatic values. They are likely relics of a former hydrostatic state when the Moon was closer to the Earth and had larger bulges, and they were established when stresses in a thickening lunar lithosphere could maintain the bulges against hydrostatic adjustment. We formulate the first dynamically consistent model of this process and show that bulge formation is controlled by the relative timing of lithosphere thickening and lunar orbit recession. Our models indicate that lunar fossil bulge formation was a geologically slow process lasting several hundred Myr, and was complete about 4 Ga when the Earth-Moon distance was less than ~32 Earth radii. The models demonstrate that the early Earth was significantly less dissipative to lunar tides than during the last 4 Gyr, suggesting a frozen Earth’s hydrosphere due to the faint young Sun and limited greenhouse effects in the Hadean eon prior to 4 Ga.