Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter
Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter
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DOI：
10.1016/j.icarus.2004.04.010
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发表时间：
2004-09
期刊：
影响因子：
3.2
通讯作者：
M. Wong;P. Mahaffy;S. Atreya;H. Niemann;T. Owen
中科院分区：
文献类型：
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作者：
M. Wong;P. Mahaffy;S. Atreya;H. Niemann;T. Owen
伽利略探针质谱仪 (GPMS) 的原位测量预计会限制形成云的可凝性挥发性气体：H2O、H2S 和 NH3 的丰度。然而，由于探测器入口点 (PES) 是一个异常干燥的气象系统（5 μm 热点），测量的可凝结挥发物丰度并不遵循平衡云凝结模型 (ECCM) 的规范凝结限制垂直剖面，例如 Weidenschilling 和 Lewis (1973, Icarus 20, 465–476)。相反，H2S和NH3的混合比随着深度的增加而增加，最终在远大于提升凝结水平的压力下达到充分混合的平衡水平，而深部充分混合大气中H2O的混合比无法测量。 8.9–11.7 bar GPMS 数据的深部 NH3 混合比（相对于 H2）为（6.64±2.54）×10−4，与探测器到轨道器信号衰减的 NH3 剖面一致（Folkner et al., 1998, J. Geophys. Res. 103, 22847–22856），其具有平衡水平约8巴。 GPMS 深层大气 H2S 混合比为 (8.9±2.1)×10−5，是木星硫丰度的唯一测量值，PES 平衡水平在 12 到 15.5 bar 之间。最深的水混合比测量值为(4.9±1.6)×10−4（仅相当于太阳丰度的30%左右），压力为17.6–20.9 bar，这个值可能比木星的整体水丰度小得多。木星NH3中的15N/14N比值在(2.3±0.3)×10−3处测量，可以提供原太阳氮同位素比值的最佳估计。 GPMS甲烷混合比为(2.37±0.57)×10−3；尽管甲烷不会在木星上凝结，但我们在本报告中包含了其最新分析，因为与可凝挥发分一样，它可能是以冰冷的星子形式带到木星的。我们对校准和误差分析补充的详细讨论先前报道了可冷凝挥发性混合比的 GPMS 测量（Niemann 等人，1998，J. Geophys. Res. 103, 22831–22846；Atreya 等人，1999，Planet. Space Sci. 47, 1243–1262；Atreya 等人，2003，Planet. Space科学51， 105–112）和氮同位素比（Owen 等人，2001b，Astrophys. J. Lett. 553，L77–L79）。 NH3（以及 CH4 和 H2S）的丰度大约为太阳丰度的三倍，这与温度 <40 K 时形成的冰冷星子对木星大气层的富集一致（Owen 等人，1999，Nature 402 (6759), 269–270），但也意味着 H2O 的丰度也应至少是太阳丰度的 3 倍。另一种模型使用笼形水合物将氮成分输送到木星，预测 O/H⩾9×太阳（Gautier 等人，2001，Astrophys. J. 550 (2)，L227–L230）。最后我们表明，只有当基本状态（预拉伸柱或夹带源区域）由比平衡云凝结模型中更干燥的可凝挥发分垂直剖面描述时，PES中测量的可凝挥发分垂直剖面才与柱拉伸或夹带下沉气流情景一致。这种干燥得到了许多遥感结果的支持，但似乎与氨和硫化氢平衡云凝结模型预测的压力水平下木星上广泛云层的观测结果不一致。
The in situ measurements of the Galileo Probe Mass Spectrometer (GPMS) were expected to constrain the abundances of the cloud-forming condensible volatile gases: H2O, H2S, and NH3. However, since the probe entry site (PES) was an unusually dry meteorological system—a 5-μm hotspot—the measured condensible volatile abundances did not follow the canonical condensation-limited vertical profiles of equilibrium cloud condensation models (ECCMs) such as Weidenschilling and Lewis (1973, Icarus 20, 465–476). Instead, the mixing ratios of H2S and NH3increased with depth, finally reaching well-mixed equilibration levels at pressures far greater than the lifting condensation levels, whereas the mixing ratio of H2O in the deep well-mixed atmosphere could not be measured. The deep NH3mixing ratio (with respect to H2) of (6.64±2.54)×10−4from 8.9–11.7 bar GPMS data is consistent with the NH3profile from probe-to-orbiter signal attenuation (Folkner et al., 1998, J. Geophys. Res. 103, 22847–22856), which had an equilibration level of about 8 bar. The GPMS deep atmosphere H2S mixing ratio of (8.9±2.1)×10−5is the only measurement of Jupiter's sulfur abundance, with a PES equilibration level somewhere between 12 and 15.5 bar. The deepest water mixing ratio measurement is (4.9±1.6)×10−4(corresponding to only about 30% of the solar abundance) at 17.6–20.9 bar, a value that is probably much smaller than Jupiter's bulk water abundance. The15N/14N ratio in jovian NH3was measured at (2.3±0.3)×10−3and may provide the best estimate of the protosolar nitrogen isotopic ratio. The GPMS methane mixing ratio is (2.37±0.57)×10−3; although methane does not condense on Jupiter, we include its updated analysis in this report because like the condensible volatiles, it was presumably brought to Jupiter in icy planetesimals. Our detailed discussion of calibration and error analysis supplements previously reported GPMS measurements of condensible volatile mixing ratios (Niemann et al., 1998, J. Geophys. Res. 103, 22831–22846; Atreya et al., 1999, Planet. Space Sci. 47, 1243–1262; Atreya et al., 2003, Planet. Space Sci. 51, 105–112) and the nitrogen isotopic ratio (Owen et al., 2001b, Astrophys. J. Lett. 553, L77–L79). The approximately three times solar abundance of NH3(along with CH4and H2S) is consistent with enrichment of Jupiter's atmosphere by icy planetesimals formed at temperatures <40 K (Owen et al., 1999, Nature 402 (6759), 269–270), but would imply that H2O should be at least 3×solar as well. An alternate model, using clathrate hydrates to deliver the nitrogen component to Jupiter, predicts O/H⩾9×solar (Gautier et al., 2001, Astrophys. J. 550 (2), L227–L230). Finally we show that the measured condensible volatile vertical profiles in the PES are consistent with column-stretching or entraining downdraft scenarios only if the basic state (the pre-stretched column or the entrainment source region) is described by condensible volatile vertical profiles that are drier than those in the equilibrium cloud condensation models. This dryness is supported by numerous remote sensing results but seems to disagree with observations of widespread clouds on Jupiter at pressure levels predicted by equilibrium cloud condensation models for ammonia and H2S.