Colors of Extreme Exo-Earth Environments

Hegde, Siddharth; Kaltenegger, Lisa

doi:10.1089/ast.2012.0849

Cited by 54 publications

(32 citation statements)

References 60 publications

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“…Toward lower wavelengths, radiation in the UV regime is capable of causing extensive damage to nucleic acids, proteins, and lipids of any carbon-based life forms that dwell on the planetary surface (13). In addition, recent studies show that planet characterizability (3,14) is usually excellent in the visible waveband, which is useful in distinguishing different surface features. Finally, reflection spectra of microbes in the near-infrared (up to 2.5 μm) portion are thought to have absorption features unique to life owing to their water of hydration and biomolecular components (10).…”

Section: Discussionmentioning

confidence: 99%

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Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

Hegde

Paulino-Lima

Kent

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Exoplanet discovery has made remarkable progress, with the first rocky planets having been detected in the central star's liquid water habitable zone. The remote sensing techniques used to characterize such planets for potential habitability and life rely solely on our understanding of life on Earth. The vegetation red edge from terrestrial land plants is often used as a direct signature of life, but it occupies only a small niche in the environmental parameter space that binds life on present-day Earth and has been widespread for only about 460 My. To more fully exploit the diversity of the one example of life known, we measured the spectral characteristics of 137 microorganisms containing a range of pigments, including ones isolated from Earth's most extreme environments. Our database covers the visible and near-infrared to the short-wavelength infrared (0.35-2.5 μm) portions of the electromagnetic spectrum and is made freely available from biosignatures. astro.cornell.edu. Our results show how the reflectance properties are dominated by the absorption of light by pigments in the visible portion and by strong absorptions by the cellular water of hydration in the infrared (up to 2.5 μm) portion of the spectrum. Our spectral library provides a broader and more realistic guide based on Earth life for the search for surface features of extraterrestrial life. The library, when used as inputs for modeling disk-integrated spectra of exoplanets, in preparation for the next generation of space-and ground-based instruments, will increase the chances of detecting life.biosignatures | spectral library | reflectivity | extremophiles | pigments I n the last decade, the field of exoplanet research has transitioned rapidly from detection to detection and characterization, with the first rocky exoplanets detected in the central star's liquid water habitable zone. Much of the excitement of this research in both the astrobiology community and the general public is motivated by the quest to discover a second genesis of life. The great distances that separate us from even the most nearby stars dictate that all measurements of the exoplanet must be made through remote sensing techniques for the foreseeable future. Thus, it is critical for us to determine the types of biosignatures that we should be looking for when designing the next generation of ground-and space-based instruments that will observe these planets at high spectral and possibly spatial resolutions.Since the mid-1960s a primary life-searching strategy has been to look for a specific combination of an oxidizing and a reducing gas in the exoplanetary atmosphere, such as the O 2 and CH 4 in our atmosphere, because this is a thermodynamically unstable situation suggesting that an active agent such as life is responsible for the chemical disequilibrium (1, 2). Of particular interest, both from an observational and modeling perspective, is to complement those indirect life detection studies with surface features that are direct properties of the organisms themselves (3).Alt...

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Section: Discussionmentioning

confidence: 99%

“…Of particular interest, both from an observational and modeling perspective, is to complement those indirect life detection studies with surface features that are direct properties of the organisms themselves (3).…”

mentioning

confidence: 99%

Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

Hegde

Paulino-Lima

Kent

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…The first method relies on surface-dwelling life having molecules that absorb in regions of the spectrum to yield spectral features not expected from known abiotic materials (Hegde and Kaltenegger 2013;Kiang et al 2007aKiang et al , 2007b. A particularly strong candidate is the red edge of chlorophyll, which is a distinctive surface feature of vegetation on planet Earth (Seager et al 2005;Tinetti et al 2006) indicating complex life form which were however not present on the early Earth.…”

Section: Around Other Stars?mentioning

confidence: 99%

Astrobiology and the Possibility of Life on Earth and Elsewhere…

et al. 2015

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Astrobiology is an interdisciplinary scientific field not only focused on the search of extraterrestrial life, but also on deciphering the key environmental parameters that have enabled the emergence of life on Earth. Understanding these physical and chemical parameters is fundamental knowledge necessary not only for discovering life or signs of life on other planets, but also for understanding our own terrestrial environment. Therefore, astrobiology pushes us to combine different perspectives such as the conditions on the primitive Earth, the Team of interdisciplinary scientists focused on astrobiology to review the profound transformations in the field that have occurred since the beginning of the new century. The present paper is an interdisciplinary review of current research in astrobiology, covering the major advances and main outlooks in the field. The following subjects will be reviewed and most recent discoveries will be highlighted: the new understanding of planetary system formation including the specificity of the Earth among the diversity of planets, the origin of water on Earth and its unique combined properties among solvents for the emergence of life, the idea that the Earth could have been habitable during the Hadean Era, the inventory of endogenous and exogenous sources of organic matter and new concepts about how chemistry could evolve towards biological molecules and biological systems. In addition, many new findings show the remarkable potential life has for adaptation and survival in extreme environments. All those results from different fields of science are guiding our perspectives and strategies to look for life in other Solar System objects as well as beyond, in extrasolar worlds.

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“…Hypersaline conditions exist in other planets of our solar system. Salt deposits have been formed by evaporation of the primitive oceans on Mars and the oceans lying just beneath the frozen surfaces of Europa and Enceladus, the moons of Jupiter and Saturn are believed to be hypersaline (9,(41)(42)(43)(44). Terrestrial environments can be quite similar to such planetary conditions.…”

Section: Halophiles: Model Organisms In Exobiology and Environmental mentioning

confidence: 99%

New insights into microbial adaptation to extreme saline environments

Vauclare

Madern²,

Girard³

et al. 2014

BIO Web of Conferences

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Abstract. Extreme halophiles are microorganisms adapted to low water activity living at the upper salt concentration that life can tolerate. We review here recent data that specify the main factors, which determine their peculiar salt-dependent biochemistry. The data suggested that evolution proceeds by stage to modify the molecular dynamics properties of the entire proteome. Extreme halophiles therefore represent tractable models to understand how fast and to what extent microorganisms adapt to environmental changes. Halophiles are also robust organisms, capable to resist multiple stressors. Preliminary studies indicated that they have developed a cellular response specifically aimed to survive when the salt condition fluctuates. Because of these properties halophilic organisms deserve special attention in the search for traces of life on other planets.

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Colors of Extreme Exo-Earth Environments

Cited by 54 publications

References 60 publications

Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

Surface biosignatures of exo-Earths: Remote detection of extraterrestrial life

Astrobiology and the Possibility of Life on Earth and Elsewhere…

New insights into microbial adaptation to extreme saline environments

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