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

Abstract: 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: ligiacoelho@tecnico.ulisboa.pt

Calibrated Data - 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). 

Raw Data - 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.  

Reference Data - 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. 

Affiliations 

1. Centro de Química Estrutural, Departamento de Engenharia Química, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
2. Institute for Bioengineering and Biosciences, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal.
3. Department of Astronomy, Cornell University, Ithaca, New York, USA.
4. Carl Sagan Institute, Ithaca, New York, USA.
5. Department of Microbiology, Cornell University, Ithaca, New York, USA.
6. School of Civil and Environmental Engineering, Cornell University, Ithaca, New York, USA.
7. Landscape, Environment, Agriculture and Food—LEAF Centre, Instituto Superior de Agronomia, Universidade de Lisboa, Lisboa, Portugal.
8. Centre for Northern Studies (CEN), Takuvik & Biology Department, Université Laval, Québec, Canada.