Color Catalogue of Life in Ice: Surface Biosignatures on Icy Worlds

<strong>Abstract</strong>: With thousands of discovered planets orbiting other stars and new missions that will explore our solar system, the search for life in the universe has entered a new era. However, a reference database to enable our search for life on the surface of icy exoplanets and exomoons by using records from Earth’s icy biota is missing. Therefore, we developed a spectra catalogue of life in ice to facilitate the search for extraterrestrial signs of life. We measured the reflection spectra of 80 microorganisms—with a wide range of pigments—isolated from ice and water. We show that carotenoid signatures are wide-ranged and intriguing signs of life. Our measurements allow for the identification of such surface life on icy extraterrestrial environments in preparation for observations with the upcoming ground- and space-based telescopes. Dried samples reveal even higher reflectance, which suggests that signatures of surface biota could be more intense on exoplanets and moons that are drier than Earth or on environments like Titan where potential life-forms may use a different solvent. Our spectral library covers the visible to near-infrared and is available online. It provides a guide for the search for surface life on icy worlds based on biota from Earth’s icy environments. Research Article: https://doi.org/10.1089/ast.2021.0008 Email: [e-mail] <strong>Calibrated Data</strong> - Folders organized by sample Filenames key: {month}.{day}.{sample identifier}.{dryness}.cal.txt For sample dryness "f" stands for "fresh", measurement was collected while the sample was still wet from preparation. "w" stands for "week", measurement was collected after a week of drying time. "cal" identifies that the data has been calibrated as described in the methods section of the linked article and results section of Hegde et al. (2015). <strong>Raw Data</strong> - Folders organized by sample Filenames key: {month}.{day}.{sample identifier}.{dryness}.B.txt For sample dryness "f" stands for "fresh", measurement was collected while the sample was still wet from preparation. "w" stands for "week", measurement was collected after a week of drying time. "B" identifies the black background used during sample measurement which is calibrated for using data in the Reference Data folder. <strong>Reference Data</strong> - Folders organized by reference type Controls - calibrated control samples same filename format as calibrated data. Blank sample, fresh (f) and week old (w), with a black background. DarkReference - Measurements of the dark background used to hold samples. No sample, black background only. LightTrap - Measurement of the light trap. No background. TargetReference - Service file for the white reference used. WhiteReference - White reference measurements by date. White reference only. <strong>Affiliations </strong> Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal. Department of Astronomy, Cornell University, Ithaca, New York, USA. Carl Sagan Institute, Ithaca, New York, USA. Department of Microbiology, Cornell University, Ithaca, New York, USA. School of Civil and Environmental Engineering, Cornell University, Ithaca, New York, USA. Landscape, Environment, Agriculture and Food—LEAF Centre, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal. Centre for Northern Studies (CEN), Takuvik &amp; Biology Department, Université Laval, Québec, Canada.摘要：随着数千颗系外行星（exoplanets）被发现，以及多项即将探索太阳系的新任务陆续开展，宇宙生命搜寻工作已迈入全新阶段。然而，目前仍缺乏可借助地球冰境生物记录，搜寻冰态系外行星与系外卫星（exomoons）表面生命的参考数据库。为此，本研究构建了冰中生命光谱目录，以助力地外生命信号的搜寻工作。 研究团队对从冰体与水体中分离得到的80种含多样色素的微生物进行了反射光谱测量。研究表明，类胡萝卜素（carotenoid）特征光谱是分布广泛且极具研究价值的生命信号。本测量结果可用于识别冰态地外环境中的此类表面生命，为即将启用的地面与空间望远镜观测做好准备。 干燥样品的反射率更高，这表明在比地球更干燥的系外行星与卫星，或是如土卫六（Titan）这类潜在生命可能使用不同溶剂的环境中，表面生物的特征信号可能会更强。 本光谱库覆盖可见光至近红外（near-infrared）波段，且已在线公开。该库可为基于地球冰境生物，搜寻冰态天体表面生命提供参考依据。 研究论文：https://doi.org/10.1089/ast.2021.0008 电子邮箱：[e-mail] ## 校准数据 按样品分类的文件夹，文件名格式为：{月}.{日}.{样品编号}.{干湿状态}.cal.txt 其中干湿状态参数：'f'代表新鲜样品，即样品制备后仍处于湿润状态时采集的测量数据；'w'代表风干一周后的样品，即经过一周干燥时间后采集的测量数据；后缀'cal'表明该数据已按照本文研究方法及Hegde等人（2015）的结果章节所述流程完成校准。 ## 原始数据 按样品分类的文件夹，文件名格式为：{月}.{日}.{样品编号}.{干湿状态}.B.txt 干湿状态参数含义与校准数据部分一致；后缀'B'代表样品测量时使用的黑色背景，该背景的校准数据可参考参考数据文件夹中的相关文件。 ## 参考数据 按参考类型分类的文件夹： - 对照样品（Controls）：已校准的对照样品，文件名格式与校准数据一致，包含新鲜（f）与风干一周（w）的空白样品（无微生物），搭配黑色背景。 - 暗参考（DarkReference）：用于承载样品的暗背景测量数据，无样品，仅含黑色背景。 - 光阱（LightTrap）：光阱的测量数据，无背景。 - 目标参考（TargetReference）：所用白色参考的配套文件。 - 白色参考（WhiteReference）：按日期分类的白色参考测量数据，仅含白色参考板。 ## 作者单位 1. 葡萄牙里斯本大学高等理工学院化学工程系结构化学中心 2. 葡萄牙里斯本大学高等理工学院生物工程与生物科学研究所 3. 美国纽约州伊萨卡康奈尔大学天文系 4. 美国纽约州伊萨卡卡尔·萨根研究所 5. 美国纽约州伊萨卡康奈尔大学微生物学系 6. 美国纽约州伊萨卡康奈尔大学土木与环境工程学院 7. 葡萄牙里斯本大学高等农学院景观、环境、农业与食品研究中心（LEAF中心） 8. 加拿大魁北克拉瓦尔大学北方研究中心（CEN）、Takuvik研究所与生物系