Piqueux Sylvain, Müller Nils, Grott Matthias, Siegler Matthew, Millour Ehouarn, Forget Francois, Lemmon Mark, Golombek Matthew, Williams Nathan, Grant John, Warner Nicholas, Ansan Veronique, Daubar Ingrid, Knollenberg Jörg, Maki Justin, Spiga Aymeric, Banfield Don, Spohn Tilman, Smrekar Susan, Banerdt Bruce
Jet Propulsion Laboratory California Institute of Technology Pasadena CA USA.
DLR Institute for Planetary Research Berlin Germany.
J Geophys Res Planets. 2021 Aug;126(8):e2021JE006859. doi: 10.1029/2021JE006859. Epub 2021 Aug 12.
Measurements from the InSight lander radiometer acquired after landing are used to characterize the thermophysical properties of the Martian soil in Homestead hollow. This data set is unique as it stems from a high measurement cadence fixed platform studying a simple well-characterized surface, and it benefits from the environmental characterization provided by other instruments. We focus on observations acquired before the arrival of a regional dust storm (near Sol 50), on the furthest observed patch of soil (i.e., ∼3.5 m away from the edge of the lander deck) where temperatures are least impacted by the presence of the lander and where the soil has been least disrupted during landing. Diurnal temperature cycles are fit using a homogenous soil configuration with a thermal inertia of 183 ± 25 J m K s and an albedo of 0.16, corresponding to very fine to fine sand with the vast majority of particles smaller than 140 μm. A pre-landing assessment leveraging orbital thermal infrared data is consistent with these results, but our analysis of the full diurnal temperature cycle acquired from the ground further indicates that near surface layers with different thermophysical properties must be thin (i.e., typically within the top few mm) and deep layering with different thermophysical properties must be at least below ∼4 cm. The low thermal inertia value indicates limited soil cementation within the upper one or two skin depths (i.e., ∼4-8 cm and more), with cement volumes <<1%, which is challenging to reconcile with visible images of overhangs in pits.
洞察号着陆器着陆后获取的辐射计测量数据，用于表征家园洼地火星土壤的热物理性质。该数据集独一无二，因为它源于一个具有高测量频率的固定平台，该平台研究的是一个特征明确的简单表面，并且受益于其他仪器提供的环境特征描述。我们重点关注在一场区域沙尘暴到来之前（接近第50个火星日）获取的观测数据，这些数据来自观测到的最远处的土壤斑块（即距离着陆器甲板边缘约3.5米处），在那里温度受着陆器存在的影响最小，且土壤在着陆期间受到的扰动也最小。利用具有183±25焦耳·米·开尔文·秒热惯性和0.16反照率的均匀土壤配置来拟合昼夜温度循环，这对应于绝大多数颗粒小于140微米的极细到细砂。利用轨道热红外数据进行的着陆前评估与这些结果一致，但我们对从地面获取的完整昼夜温度循环的分析进一步表明，具有不同热物理性质的近地表层必定很薄（即通常在顶部几毫米内），而具有不同热物理性质的深层必定至少在约4厘米以下。低热惯性值表明在一两个趋肤深度（即约4 - 8厘米及更深）范围内土壤胶结作用有限，胶结体积远小于1%，这很难与坑中悬垂物的可见光图像相协调。
