Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. Southwest Research Institute, 6220 Culebra Road, San Antonio, TX 78238, USA.
Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland. Center for Space and Habitability (CSH), University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland.
Science. 2015 Jan 23;347(6220):aaa0276. doi: 10.1126/science.aaa0276. Epub 2015 Jan 22.
Comets contain the best-preserved material from the beginning of our planetary system. Their nuclei and comae composition reveal clues about physical and chemical conditions during the early solar system when comets formed. ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) onboard the Rosetta spacecraft has measured the coma composition of comet 67P/Churyumov-Gerasimenko with well-sampled time resolution per rotation. Measurements were made over many comet rotation periods and a wide range of latitudes. These measurements show large fluctuations in composition in a heterogeneous coma that has diurnal and possibly seasonal variations in the major outgassing species: water, carbon monoxide, and carbon dioxide. These results indicate a complex coma-nucleus relationship where seasonal variations may be driven by temperature differences just below the comet surface.
彗星包含了太阳系形成之初保存最完好的物质。它们的核和彗发成分揭示了彗星形成时早期太阳系的物理和化学条件的线索。罗塞塔飞船上的 ROSINA（罗塞塔轨道飞行器离子和中性分析光谱仪）以每旋转一次的时间分辨率对 67P/楚留莫夫-格拉希门克彗星的彗发成分进行了很好采样的测量。这些测量是在许多彗星自转周期和广泛的纬度范围内进行的。这些测量结果表明，彗发的成分存在很大的波动，这是一种不均匀的彗发，其中主要的出气物种——水、一氧化碳和二氧化碳——存在昼夜和可能的季节性变化。这些结果表明彗核关系复杂，季节性变化可能是由彗星表面以下的温差驱动的。
