Cruikshank Dale P, Pendleton Yvonne J, Grundy William M
NASA Ames Research Center, Moffett Field, CA 94035, USA.
Lowell Observatory, Flagstaff, AZ 86001, USA.
Life (Basel). 2020 Jul 28;10(8):126. doi: 10.3390/life10080126.
The close encounters of the Pluto-Charon system and the Kuiper Belt object Arrokoth (formerly 2014 MU) by NASA's New Horizons spacecraft in 2015 and 2019, respectively, have given new perspectives on the most distant planetary bodies yet explored. These bodies are key indicators of the composition, chemistry, and dynamics of the outer regions of the Solar System's nascent environment. Pluto and Charon reveal characteristics of the largest Kuiper Belt objects formed in the dynamically evolving solar nebula inward of ~30 AU, while the much smaller Arrokoth is a largely undisturbed relic of accretion at ~45 AU. The surfaces of Pluto and Charon are covered with volatile and refractory ices and organic components, and have been shaped by geological activity. On Pluto, N, CO and CH are exchanged between the atmosphere and surface as gaseous and condensed phases on diurnal, seasonal and longer timescales, while Charon's surface is primarily inert HO ice with an ammoniated component and a polar region colored with a macromolecular organic deposit. Arrokoth is revealed as a fused binary body in a relatively benign space environment where it originated and has remained for the age of the Solar System. Its surface is a mix of CHOH ice, a red-orange pigment of presumed complex organic material, and possibly other undetected components.
美国国家航空航天局（NASA）的“新视野号”航天器分别于2015年和2019年对冥王星-卡戎系统以及柯伊伯带天体“天涯海角”（原名2014 MU）进行了近距离探测，为迄今已探索的最遥远行星天体带来了新的视角。这些天体是太阳系初始环境外部区域组成、化学和动力学的关键指标。冥王星和卡戎揭示了在动态演化的太阳星云内距离约30天文单位处形成的最大柯伊伯带天体的特征，而小得多的“天涯海角”则是在约45天文单位处基本未受干扰的吸积遗迹。冥王星和卡戎的表面覆盖着挥发性和难熔性冰以及有机成分，并受到地质活动的塑造。在冥王星上，氮、一氧化碳和甲烷在大气和表面之间以气态和凝聚态在昼夜、季节和更长时间尺度上进行交换，而卡戎的表面主要是惰性的水冰，带有氨化成分和一个由大分子有机沉积物染色的极地地区。“天涯海角”在其起源并在太阳系存在至今的相对温和的空间环境中被揭示为一个融合的双星天体。它的表面是甲醇冰、一种推测为复杂有机物质的红橙色色素以及可能其他未检测到的成分的混合物。
