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| Paper: |
Detecting Alien Living Worlds and Photosynthetic Life using Imaging Polarimetry with the HWO Coronagraph |
| Monograph: |
10, HWO25 Proceedings Part I: Community Science Case Development Documents |
| Page: |
331 |
| Authors: |
Svetlana Berdyugina; Lucas Patty; Jonathan Grone; Brice Demory; Kim Bott; Vincent Kofman; Giulia Roccetti; Kenneth Goodis Gordon; Frans Snik; Theodora Karalidi; Victor Trees; Daphne Stam; Mary N. Parenteau |
| DOI: |
10.26624/LNJL1138 |
| Abstract: |
Our Earth, being the only living planet that we know, provides us with clues that photosynthetic
life-forms may be dominant on other exoplanets for billions of years. Spectropolarimetric signatures of
the terrestrial photosynthetic life (PSLife) are well studied in the lab and remotely sensed with space and
airborne instrumentation. An astonishing biosignature revealed by these measurements is an extremely strong
linear polarization (tens %) associated with broad absorption bands of biological pigments (biopigments)
driving photosynthesis in various organisms. Also, unique circular-polarization signatures are associated with
biopigments and other complex macromolecules as a sign of homochirality which is ubiquitous in terrestrial
life forms. Thus, low-resolution spectro- or multi-band polarimetry of exoplanets directly imaged at an
unprecedented contrast using the HWO coronagraph is a novel opportunity for a robust discovery of life
on exoplanets. Here we propose to carry out two surveys and two follow-up observing programs. Survey
1 will identify potentially habitable planets (PHPs) through detection of atmospheres, clouds and liquid
surface water (ocean) using linear polarimetry. Survey 2 will identify Living World (LW) candidates among
PHPs by searching for strong linear polarization signatures associated with strong and broad absorption
bands reminiscent of terrestrial biopigments. Follow-up program 3 will obtain multi-color surface maps
of LWs, determine the distribution and abundance of alien photosynthetic organisms with exo-biopigments
(exoBPs) and correlate their properties with the atmospheric and surface compositions. Follow-up program 4
will employ circular polarization to verify homochirality of exoBPs. This comprehensive approach aims at
providing a quantitative answer to the ultimate question ”Are we are alone in the Universe?” |
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