Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA
Mapping Vinyl Cyanide and Other Nitriles in Titan’s Atmosphere Using ALMA
复制标题
使用 ALMA 绘制土卫六大气中的乙烯基氰和其他腈的图谱
DOI：
10.3847/1538-3881/aa8eef
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
P. Irwin
中科院分区：
文献类型：
--
作者：
J. Lai;M. Cordiner;C. Nixon;R. Achterberg;E. Molter;N. Teanby;M. Palmer;S. Charnley;J. Lindberg;Z. Kisiel;M. Mumma;P. Irwin
乙烯基氰化物（C2 H3CN）理论上是在泰坦的大气中通过高空光化学形成的，并且由于其在液态甲烷中形成细胞膜状结构（偶氮体）的预测能力，因此对寒冷行星表面的天体生物学很感兴趣。在这项工作中，我们跟进了Palmer等人在Titan上对C2 H3CN的初始光谱检测，在亚毫米频率下检测到三条新的C2 H3CN旋转发射线。这些新的、高分辨率的探测使得首次绘制出泰坦上C2 H3CN的空间分布图成为可能。我们提出了同时观测C2 H5 CN，HC 3 N，和CH 3CN的排放，并获得第一个（暂定）检测C3 H8（丙烷）在无线电波长。我们目前的磁盘平均垂直丰度剖面，二维空间地图，和纬度通量剖面所观察到的腈。类似于HC 3 N和C2 H5 CN，理论上它们在土卫六大气中的寿命很短，C2 H3CN在南极（冬季）最丰富，而寿命较长的CH 3CN则更多地集中在北部。这种丰富的模式是一致的高海拔光化学生产的综合影响，向极平流，以及随后的逆转泰坦的大气环流系统后，最近从北方到南方的冬天。我们确认C2 H3CN和C2 H5 CN在200 km以上的高度最丰富。使用300 km台阶模型，发现C2 H3CN的平均丰度为3.03 ± 0.29 ppb，C2 H5 CN/C2 H3CN丰度比为2.43 ± 0.26。我们的HC 3 N和CH 3CN光谱可以准确地使用对流层顶以上的丰度梯度，分数标度高度分别为2.05 ± 0.16和1.63 ± 0.02。
Vinyl cyanide (C2H3CN) is theorized to form in Titan’s atmosphere via high-altitude photochemistry and is of interest regarding the astrobiology of cold planetary surfaces due to its predicted ability to form cell membrane-like structures (azotosomes) in liquid methane. In this work, we follow up on the initial spectroscopic detection of C2H3CN on Titan by Palmer et al. with the detection of three new C2H3CN rotational emission lines at submillimeter frequencies. These new, high-resolution detections have allowed for the first spatial distribution mapping of C2H3CN on Titan. We present simultaneous observations of C2H5CN, HC3N, and CH3CN emission, and obtain the first (tentative) detection of C3H8 (propane) at radio wavelengths. We present disk-averaged vertical abundance profiles, two-dimensional spatial maps, and latitudinal flux profiles for the observed nitriles. Similarly to HC3N and C2H5CN, which are theorized to be short-lived in Titan’s atmosphere, C2H3CN is most abundant over the southern (winter) pole, whereas the longer-lived CH3CN is more concentrated in the north. This abundance pattern is consistent with the combined effects of high-altitude photochemical production, poleward advection, and the subsequent reversal of Titan’s atmospheric circulation system following the recent transition from northern to southern winter. We confirm that C2H3CN and C2H5CN are most abundant at altitudes above 200 km. Using a 300 km step model, the average abundance of C2H3CN is found to be 3.03 ± 0.29 ppb, with a C2H5CN/C2H3CN abundance ratio of 2.43 ± 0.26. Our HC3N and CH3CN spectra can be accurately modeled using abundance gradients above the tropopause, with fractional scale-heights of 2.05 ± 0.16 and 1.63 ± 0.02, respectively.
DOI：
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发表时间：
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期刊：
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影响因子：
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作者：
通讯作者：
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影响因子：
7.9
作者：
Cordiner, M. A.;Palmer, M. Y.;Wang, K. -S.
通讯作者：
Wang, K. -S.