Park R S, Berne A, Konopliv A S, Keane J T, Matsuyama I, Nimmo F, Rovira-Navarro M, Panning M P, Simons M, Stevenson D J, Weber R C
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA.
Seismological Laboratory, California Institute of Technology, Pasadena, CA, USA.
Nature. 2025 May;641(8065):1188-1192. doi: 10.1038/s41586-025-08949-5. Epub 2025 May 14.
The Moon undergoes periodic tidal forcing due to its eccentric and oblique orbit around the Earth. The response to this tidal interaction drives temporal changes in the lunar gravity field and is sensitive to the satellite's internal structure. We use data from the NASA GRAIL spacecraft to recover the time-varying lunar gravity field, including a degree-3 gravitational tidal Love number, k. Here, we report our estimated value of k = 0.0163 ± 0.0007, which is about 72% higher than that expected for a spherically symmetric moon. Such a large k can be explained if the elastic shear modulus of the mantle varies by about 2-3% between the nearside and farside, providing an observational demonstration of lateral heterogeneities in the deep lunar interior. This asymmetric structure suggests preservation of a predominantly thermal anomaly of roughly 100-200 K in the nearside mantle that formed surface mare regions 3-4 billion years ago and could influence the spatial distribution of deep moonquakes.
由于月球绕地球的轨道偏心且倾斜，月球会受到周期性的潮汐力作用。对这种潮汐相互作用的响应驱动了月球重力场的时间变化，并且对卫星的内部结构很敏感。我们使用美国国家航空航天局（NASA）圣杯号航天器的数据来恢复随时间变化的月球重力场，包括一个3阶引力潮汐勒夫数k。在此，我们报告我们估计的k值为0.0163±0.0007，这比球形对称月球预期的值高出约72%。如果地幔的弹性剪切模量在近月面和远月面之间变化约2 - 3%，那么如此大的k值就可以得到解释，这为月球深部内部的横向非均匀性提供了一个观测证据。这种不对称结构表明，在近月面地幔中大致保留了一个100 - 200K的主要热异常，该热异常在30 - 40亿年前形成了月海区域，并且可能影响深部月震的空间分布。
