Airapetian Vladimir S, Jackman Charles H, Mlynczak Martin, Danchi William, Hunt Linda
NASA/GSFC, Greenbelt, MD, USA.
American University, Washington, DC, USA.
Sci Rep. 2017 Nov 2;7(1):14141. doi: 10.1038/s41598-017-14192-4.
The current explosion in detection and characterization of thousands of extrasolar planets from the Kepler mission, the Hubble Space Telescope, and large ground-based telescopes opens a new era in searches for Earth-analog exoplanets with conditions suitable for sustaining life. As more Earth-sized exoplanets are detected in the near future, we will soon have an opportunity to identify habitale worlds. Which atmospheric biosignature gases from habitable planets can be detected with our current capabilities? The detection of the common biosignatures from nitrogen-oxygen rich terrestrial-type exoplanets including molecular oxygen (O), ozone (O), water vapor (HO), carbon dioxide (CO), nitrous oxide (NO), and methane (CH) requires days of integration time with largest space telescopes, and thus are very challenging for current instruments. In this paper we propose to use the powerful emission from rotational-vibrational bands of nitric oxide, hydroxyl and molecular oxygen as signatures of nitrogen, oxygen, and water rich atmospheres of terrestrial type exoplanets "highlighted" by the magnetic activity from young G and K main-sequence stars. The signals from these fundamental chemical prerequisites of life we call atmospheric "beacons of life" create a unique opportunity to perform direct imaging observations of Earth-sized exoplanets with high signal-to-noise and low spectral resolution with the upcoming NASA missions.
开普勒任务、哈勃太空望远镜以及大型地面望远镜目前在探测和表征数千颗系外行星方面取得的进展，开启了寻找与地球类似、具备适宜生命存在条件的系外行星的新纪元。随着在不久的将来探测到更多地球大小的系外行星，我们很快将有机会识别出宜居世界。凭借我们目前的能力，能够探测到宜居行星的哪些大气生物特征气体呢？要探测富含氮氧的类地型系外行星的常见生物特征，包括分子氧（O）、臭氧（O）、水蒸气（HO）、二氧化碳（CO）、一氧化二氮（NO）和甲烷（CH），需要使用最大的太空望远镜进行数天的积分时间观测，因此对于当前仪器来说极具挑战性。在本文中，我们提议利用一氧化氮、羟基和分子氧的转动 - 振动带发出的强大辐射，作为富含氮、氧和水的类地型系外行星大气的特征，这些行星被年轻的G型和K型主序星的磁活动“突显”出来。我们将这些生命基本化学先决条件产生的信号称为大气“生命灯塔”，这为利用美国国家航空航天局（NASA）即将开展的任务，以高信噪比和低光谱分辨率对地球大小的系外行星进行直接成像观测创造了独特机会。
