Saturn layered structure and homogeneous evolution models with different EOSs
Saturn layered structure and homogeneous evolution models with different EOSs
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DOI：
10.1016/j.icarus.2013.04.018
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发表时间：
2013-04
期刊：
影响因子：
3.2
通讯作者：
N. Nettelmann;Robert Püstow;R. Redmer
中科院分区：
文献类型：
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作者：
N. Nettelmann;Robert Püstow;R. Redmer
土星的核心质量通常被假设为10- 25 M质量，这是由内部模型和各种状态方程（EOS）以及旅行者号的重力数据预测的，因此大于木星的核心质量（0- 10 M质量）。在这里，我们重新分析土星的内部结构和演变，使用更近的重力数据从卡西尼号使命和不同的物理状态方程：从头LM-REOS，这是相当软的土星的外部区域，但在高压下僵硬，标准芝麻EOS显示相反的行为，和常用的SCvH-i EOS。对于所有三种EOS，我们发现类似的核心质量范围，即SCvH-i和芝麻EOS为0- 20 M质量，LM-REOS为0- 17 M质量。假设大气中氦的质量丰度为18%，我们发现最大大气金属丰度，SCvH-i和芝麻模型的Zatmof 7×太阳，重元素的总质量，MZ为25- 30 M。有些模型是类似于反射器的。用LM-REOS，我们发现MZ=16- 20 M，比木星小，Zatm = 3×太阳。对于土星，我们计算出转动惯量值λ=0.2355（5）。此外，我们确认，均匀演化导致冷却时间只有2.5Gyr，独立于所应用的状态方程。我们的研究结果表明，需要准确测量大气中的氦和氧的丰度，以及更好地了解土星的结构和演变的惯性矩。
The core mass of Saturn is commonly assumed to be 10–25M⊕as predicted by interior models with various equations of state (EOSs) and the Voyager gravity data, and hence larger than that of Jupiter (0–10M⊕). We here re-analyze Saturn’s internal structure and evolution by using more recent gravity data from the Cassini mission and different physical equations of state: the ab initio LM-REOS which is rather soft in Saturn’s outer regions but stiff at high pressures, the standard Sesame-EOS which shows the opposite behavior, and the commonly used SCvH-i EOS. For all three EOS we find similar core mass ranges, i.e. of 0–20M⊕for SCvH-i and Sesame EOS and of 0–17M⊕for LM-REOS. Assuming an atmospheric helium mass abundance of 18%, we find maximum atmospheric metallicities, Zatmof 7× solar for SCvH-i and Sesame-based models and a total mass of heavy elements, MZof 25–30M⊕. Some models are Jupiter-like. With LM-REOS, we find MZ=16–20M⊕, less than for Jupiter, and Zatm≲3× solar. For Saturn, we compute moment of inertia values λ=0.2355(5). Furthermore, we confirm that homogeneous evolution leads to cooling times of only ∼2.5Gyr, independent on the applied EOS. Our results demonstrate the need for accurately measured atmospheric helium and oxygen abundances, and of the moment of inertia for a better understanding of Saturn’s structure and evolution.