The flexure of the lithosphere under stresses imposed by the geologically young south polar cap is one of the few clues we have regarding the south polar cap composition and the present-day thermal state of Mars. Here, we combine radar, gravity, and topography data with a flexural loading model to estimate the bulk density () and average real dielectric constant () of the south polar cap, and the elastic thickness of the lithosphere (). Given the uncertainties of the data, our results constrain to be 1,100–1,300 kg (best fit of 1,220 kg ), to be 2.5–3.4 (best fit of 3.3), and to be greater than 150 km (best fit of 360 km). Based on these results, the maximum lithospheric flexure is 770 m, and the polar cap volume could be up to 26% larger than previous estimates that did not account for lithospheric flexure. Our inferred compositions imply that the dust concentration would be at least 9 vol% if the ice content were negligible, and that the ice concentration would be more than the known 1 vol% if the dust concentration were less than 9 vol%. The 1- lower limit on implies a surface heat flow that is less than 23.5 mW . This lower limit is significantly less than the range of acceptable values at the north pole (330–450 km, heat flow of 11–16 mW ), and helps satisfy global thermal evolution simulations that predict hemispheric differences in surface heat flow.

中文翻译：

---

来自轨道数据的火星南极帽的组成

岩石圈在地质上年轻的南极帽施加的压力下的弯曲是我们掌握的关于南极帽组成和火星当今热状态的少数线索之一。在这里，我们将雷达、重力和地形数据与弯曲载荷模型相结合，以估计南极帽的体积密度 ( ) 和平均实际介电常数 ( ) 以及岩石圈的弹性厚度 ( )。鉴于数据的不确定性，我们的结果限制为 1,100–1,300 kg （最佳拟合为 1,220 kg ），为 2.5–3.4（最佳拟合为 3.3），并且大于 150 公里（最适合 360 公里）。根据这些结果，最大岩石圈弯曲为 770 m，极冠体积可能比先前未考虑岩石圈弯曲的估计值大 26%。我们推断的成分意味着，如果冰含量可以忽略不计，粉尘浓度将至少为 9 vol%，如果粉尘浓度小于 9 vol% ，冰浓度将高于已知的 1 vol%。1-下限意味着小于 23.5 mW 的表面热流。这个下限明显小于北极的可接受值范围（330-450 公里，热流为 11-16 mW)，并有助于满足预测半球表面热流差异的全球热演化模拟。