Laskar Jacques, Levrard Benjamin, Mustard John F
Astronomie et Systèmes Dynamiques, IMC-CNRS UMR8028, 77 Av. Denfert-Rochereau, 75014 Paris, France.
Nature. 2002 Sep 26;419(6905):375-7. doi: 10.1038/nature01066.
Since the first images of polar regions on Mars revealed alternating bright and dark layers, there has been speculation that their formation might be tied to the planet's orbital climate forcing. But uncertainties in the deposition timescale exceed two orders of magnitude: estimates based on assumptions of dust deposition, ice formation and sublimation, and their variations with orbital forcing suggest a deposition rate of 10(-3) to 10(-2) cm yr(-1) (refs 5, 6), whereas estimates based on cratering rate result in values as high as 0.1 to 0.2 cm yr(-1) (ref. 7). Here we use a combination of high-resolution images of the polar layered terrains, high-resolution topography and revised calculations of the orbital and rotational parameters of Mars to show that a correlation exists between ice-layer radiance as a function of depth (obtained from photometric data of the images of the layered terrains) and the insolation variations in summer at the martian north pole, similar to what has been shown for palaeoclimate studies of the Earth. For the best fit between the radiance profile and the simulated insolation parameters, we obtain an average deposition rate of 0.05 cm yr(-1) for the top 250 m of deposits on the ice cap of the north pole of Mars.
自从火星极地地区的首批图像揭示出明暗交替的层状结构以来，人们一直猜测其形成可能与该行星的轨道气候强迫有关。但是沉积时间尺度的不确定性超过了两个数量级：基于尘埃沉积、冰形成和升华的假设及其随轨道强迫的变化所做的估计表明沉积速率为10^(-3)至10^(-2)厘米/年（参考文献5、6），而基于撞击坑形成速率的估计得出的值高达0.1至0.2厘米/年（参考文献7）。在这里，我们结合使用极地层状地形的高分辨率图像、高分辨率地形以及对火星轨道和自转参数的修正计算，以表明冰层辐射率随深度的变化（从层状地形图像的光度数据中获得）与火星北极夏季日照变化之间存在相关性，这与地球古气候研究的情况类似。为了使辐射率剖面与模拟的日照参数达到最佳拟合，我们得出火星北极冰盖顶部250米沉积物的平均沉积速率为0.05厘米/年。
