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The search for signs of life on exoplanets at the interface of chemistry and planetary science.

Seager S, Bains W - Sci Adv (2015)

Bottom Line: The discovery of thousands of exoplanets in the last two decades that are so different from planets in our own solar system challenges many areas of traditional planetary science.However, ideas for how to detect signs of life in this mélange of planetary possibilities have lagged, and only in the last few years has modeling how signs of life might appear on genuinely alien worlds begun in earnest.Recent results have shown that the exciting frontier for biosignature gas ideas is not in the study of biology itself, which is inevitably rooted in Earth's geochemical and evolutionary specifics, but in the interface of chemistry and planetary physics.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

ABSTRACT
The discovery of thousands of exoplanets in the last two decades that are so different from planets in our own solar system challenges many areas of traditional planetary science. However, ideas for how to detect signs of life in this mélange of planetary possibilities have lagged, and only in the last few years has modeling how signs of life might appear on genuinely alien worlds begun in earnest. Recent results have shown that the exciting frontier for biosignature gas ideas is not in the study of biology itself, which is inevitably rooted in Earth's geochemical and evolutionary specifics, but in the interface of chemistry and planetary physics.

No MeSH data available.


Schematic illustration of microbial-used chemical potential energy gradients.Redox half-reactions are shown in order of their electrode potential (in volts) at pH 7.0, calculated from the standard electrode potentials for the reactions (106). Each reaction is shown as an oxidation half-reaction (left side) and as a reduction half-reaction (right side). If the oxidation of molecule A in the left column is above reduction of a molecule in the right column, then the oxidation of A can be coupled to the reduction of B yielding energy. Thus, arrows drawn between half-reactions yield energy if they run downward from left to right, and the length of the arrow indicates the amount of energy released. Coupled reactions noted in color are as follows: (1) nitrogen reduction (also nitrogen fixation or ammonia synthesis); (2) sulfate reduction (also anaerobic biomass oxidation); (3) anaerobic sulfide oxidation; (4) aerobic biomass oxidation/oxidation of organic matter/oxidation of carbohydrate; (5) aerobic sulfide oxidation; (6) aerobic ammonia oxidation; (7) aerobic iron oxidation.
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Figure 6: Schematic illustration of microbial-used chemical potential energy gradients.Redox half-reactions are shown in order of their electrode potential (in volts) at pH 7.0, calculated from the standard electrode potentials for the reactions (106). Each reaction is shown as an oxidation half-reaction (left side) and as a reduction half-reaction (right side). If the oxidation of molecule A in the left column is above reduction of a molecule in the right column, then the oxidation of A can be coupled to the reduction of B yielding energy. Thus, arrows drawn between half-reactions yield energy if they run downward from left to right, and the length of the arrow indicates the amount of energy released. Coupled reactions noted in color are as follows: (1) nitrogen reduction (also nitrogen fixation or ammonia synthesis); (2) sulfate reduction (also anaerobic biomass oxidation); (3) anaerobic sulfide oxidation; (4) aerobic biomass oxidation/oxidation of organic matter/oxidation of carbohydrate; (5) aerobic sulfide oxidation; (6) aerobic ammonia oxidation; (7) aerobic iron oxidation.

Mentions: On Earth, life exploits any chemical gradient possible (Fig. 6). A great example of this versatility is the prediction (82) and discovery 30 years later (83) of bacteria capable of anaerobic ammonia oxidation, the “annamox” reaction.


The search for signs of life on exoplanets at the interface of chemistry and planetary science.

Seager S, Bains W - Sci Adv (2015)

Schematic illustration of microbial-used chemical potential energy gradients.Redox half-reactions are shown in order of their electrode potential (in volts) at pH 7.0, calculated from the standard electrode potentials for the reactions (106). Each reaction is shown as an oxidation half-reaction (left side) and as a reduction half-reaction (right side). If the oxidation of molecule A in the left column is above reduction of a molecule in the right column, then the oxidation of A can be coupled to the reduction of B yielding energy. Thus, arrows drawn between half-reactions yield energy if they run downward from left to right, and the length of the arrow indicates the amount of energy released. Coupled reactions noted in color are as follows: (1) nitrogen reduction (also nitrogen fixation or ammonia synthesis); (2) sulfate reduction (also anaerobic biomass oxidation); (3) anaerobic sulfide oxidation; (4) aerobic biomass oxidation/oxidation of organic matter/oxidation of carbohydrate; (5) aerobic sulfide oxidation; (6) aerobic ammonia oxidation; (7) aerobic iron oxidation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4643826&req=5

Figure 6: Schematic illustration of microbial-used chemical potential energy gradients.Redox half-reactions are shown in order of their electrode potential (in volts) at pH 7.0, calculated from the standard electrode potentials for the reactions (106). Each reaction is shown as an oxidation half-reaction (left side) and as a reduction half-reaction (right side). If the oxidation of molecule A in the left column is above reduction of a molecule in the right column, then the oxidation of A can be coupled to the reduction of B yielding energy. Thus, arrows drawn between half-reactions yield energy if they run downward from left to right, and the length of the arrow indicates the amount of energy released. Coupled reactions noted in color are as follows: (1) nitrogen reduction (also nitrogen fixation or ammonia synthesis); (2) sulfate reduction (also anaerobic biomass oxidation); (3) anaerobic sulfide oxidation; (4) aerobic biomass oxidation/oxidation of organic matter/oxidation of carbohydrate; (5) aerobic sulfide oxidation; (6) aerobic ammonia oxidation; (7) aerobic iron oxidation.
Mentions: On Earth, life exploits any chemical gradient possible (Fig. 6). A great example of this versatility is the prediction (82) and discovery 30 years later (83) of bacteria capable of anaerobic ammonia oxidation, the “annamox” reaction.

Bottom Line: The discovery of thousands of exoplanets in the last two decades that are so different from planets in our own solar system challenges many areas of traditional planetary science.However, ideas for how to detect signs of life in this mélange of planetary possibilities have lagged, and only in the last few years has modeling how signs of life might appear on genuinely alien worlds begun in earnest.Recent results have shown that the exciting frontier for biosignature gas ideas is not in the study of biology itself, which is inevitably rooted in Earth's geochemical and evolutionary specifics, but in the interface of chemistry and planetary physics.

View Article: PubMed Central - PubMed

Affiliation: Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

ABSTRACT
The discovery of thousands of exoplanets in the last two decades that are so different from planets in our own solar system challenges many areas of traditional planetary science. However, ideas for how to detect signs of life in this mélange of planetary possibilities have lagged, and only in the last few years has modeling how signs of life might appear on genuinely alien worlds begun in earnest. Recent results have shown that the exciting frontier for biosignature gas ideas is not in the study of biology itself, which is inevitably rooted in Earth's geochemical and evolutionary specifics, but in the interface of chemistry and planetary physics.

No MeSH data available.