根据Rosetta/VIRTIS-H观测在近日点附近67 P彗星彗发中CO $_2$、CH PDMATHAAD和OCS丰度相对于H $_2$ O的演变
Evolution of CO$_2$, CH$_4$, and OCS abundances relative to H$_2$O in the coma of comet 67P around perihelion from Rosetta/VIRTIS-H observations
摘要：
2015年7月至9月对67 P/Churyumov-Gerasimenko的彗发进行了红外观测，即，近日点附近（2015年8月13日），使用罗塞塔号上VIRTIS仪器的高分辨率通道。本文分析了在距彗星中心2.7-5公里的观测范围内，用临边探测法探测到的H $_2$ O、CO $_2$、$^{13}$ CO $_2$、OCS和CH $_4$的荧光发射谱线。测量是从被照亮的南半球取样放气，如H $_2$ O和CO $_2$光栅图所示，其显示各向异性分布，沿投影旋转轴对齐。近日点后6天，观测到产水量突然增加。同时，CO $_2$、CH $_4$和OCS相对于水的丰度增加了2倍，分别达到32%、0.47%和0.18%的平均值，平均后近日点数据。我们解释这些变化是由于挥发性差的表面层的侵蚀。持续的灰尘消融由于水冰的升华保持挥发物丰富的层附近的表面，直到至少所考虑的期间结束，预期为低热惯性表面层。测量到的CO $_2$的大丰度应该代表了67 P核的原始组成，并表明67 P是一颗富含CO $_2$的彗星。与在北半球测得的丰度比比较表明，季节在彗星释气中起着重要作用。低CO $_2$ /H $_2$ O值测量以上的照明北半球不是原来的，但最上层的脱挥发分的结果。
英文摘要：
Infrared observations of the coma of 67P/Churyumov-Gerasimenko were carried out from July to September 2015, i.e., around perihelion (13 August 2015), with the high-resolution channel of the VIRTIS instrument onboard Rosetta. We present the analysis of fluorescence emission lines of H$_2$O, CO$_2$, $^{13}$CO$_2$, OCS, and CH$_4$ detected in limb sounding with the field of view at 2.7-5 km from the comet centre. Measurements are sampling outgassing from the illuminated southern hemisphere, as revealed by H$_2$O and CO$_2$ raster maps, which show anisotropic distributions, aligned along the projected rotation axis. An abrupt increase of water production is observed six days after perihelion. In the mean time, CO$_2$, CH$_4$, and OCS abundances relative to water increased by a factor of 2 to reach mean values of 32%, 0.47%, and 0.18%, respectively, averaging post-perihelion data. We interpret these changes as resulting from the erosion of volatile-poor surface layers. Sustained dust ablation due to the sublimation of water ice maintained volatile-rich layers near the surface until at least the end of the considered period, as expected for low thermal inertia surface layers. The large abundance measured for CO$_2$ should be representative of the 67P nucleus original composition, and indicates that 67P is a CO$_2$-rich comet. Comparison with abundance ratios measured in the northern hemisphere shows that seasons play an important role in comet outgassing. The low CO$_2$/H$_2$O values measured above the illuminated northern hemisphere are not original, but the result of the devolatilization of the uppermost layers.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
