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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.


Related in: MedlinePlus

Schematic of a transmission spectrum.Transmission spectra are created by planet atmosphere absorption imprinted on starlight passing through the planet atmosphere. (Top) Shown are a variety of different cases: deep and wide spectral features are expected from a low–molecular weight atmosphere, which presents a relatively large volume to be sampled. (Middle) In contrast, only narrow, shallow spectral features are expected from a high–molecular weight atmosphere, which results in a limited atmosphere to be sampled by the starlight. (Bottom) Clouds block starlight and may entirely prevent sampling of the dense part of the atmosphere where spectral lines form. Other situations are also possible. Many exoplanet spectra including (22) find no spectral features, consistent with clouds. Figure credit: S. Seager and D. Beckner.
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Figure 4: Schematic of a transmission spectrum.Transmission spectra are created by planet atmosphere absorption imprinted on starlight passing through the planet atmosphere. (Top) Shown are a variety of different cases: deep and wide spectral features are expected from a low–molecular weight atmosphere, which presents a relatively large volume to be sampled. (Middle) In contrast, only narrow, shallow spectral features are expected from a high–molecular weight atmosphere, which results in a limited atmosphere to be sampled by the starlight. (Bottom) Clouds block starlight and may entirely prevent sampling of the dense part of the atmosphere where spectral lines form. Other situations are also possible. Many exoplanet spectra including (22) find no spectral features, consistent with clouds. Figure credit: S. Seager and D. Beckner.

Mentions: The exoplanet community had hoped that atmosphere measurements via transmission spectroscopy would possibly be able to discriminate among the scenarios for GJ 1214b’s interior bulk composition (37, 38). An atmosphere dominated by H2 or H2/He would be puffy (have a large scale height), and with no clouds, it would show deep spectral features. In contrast, a clear atmosphere dominated by a higher–molecular weight species (H2O, N2, CO2) would have a smaller scale height than for the hydrogen atmosphere, resulting in an atmosphere with small “compressed” spectral features (Fig. 4). Clouds were not expected because at GJ 1214b’s temperature of ~580 K (predicted from a simple calculation of stellar heating and the main elements in planet atmospheres), no condensates were expected at all or to exist in high enough abundance to form blanketing clouds.


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

Seager S, Bains W - Sci Adv (2015)

Schematic of a transmission spectrum.Transmission spectra are created by planet atmosphere absorption imprinted on starlight passing through the planet atmosphere. (Top) Shown are a variety of different cases: deep and wide spectral features are expected from a low–molecular weight atmosphere, which presents a relatively large volume to be sampled. (Middle) In contrast, only narrow, shallow spectral features are expected from a high–molecular weight atmosphere, which results in a limited atmosphere to be sampled by the starlight. (Bottom) Clouds block starlight and may entirely prevent sampling of the dense part of the atmosphere where spectral lines form. Other situations are also possible. Many exoplanet spectra including (22) find no spectral features, consistent with clouds. Figure credit: S. Seager and D. Beckner.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Schematic of a transmission spectrum.Transmission spectra are created by planet atmosphere absorption imprinted on starlight passing through the planet atmosphere. (Top) Shown are a variety of different cases: deep and wide spectral features are expected from a low–molecular weight atmosphere, which presents a relatively large volume to be sampled. (Middle) In contrast, only narrow, shallow spectral features are expected from a high–molecular weight atmosphere, which results in a limited atmosphere to be sampled by the starlight. (Bottom) Clouds block starlight and may entirely prevent sampling of the dense part of the atmosphere where spectral lines form. Other situations are also possible. Many exoplanet spectra including (22) find no spectral features, consistent with clouds. Figure credit: S. Seager and D. Beckner.
Mentions: The exoplanet community had hoped that atmosphere measurements via transmission spectroscopy would possibly be able to discriminate among the scenarios for GJ 1214b’s interior bulk composition (37, 38). An atmosphere dominated by H2 or H2/He would be puffy (have a large scale height), and with no clouds, it would show deep spectral features. In contrast, a clear atmosphere dominated by a higher–molecular weight species (H2O, N2, CO2) would have a smaller scale height than for the hydrogen atmosphere, resulting in an atmosphere with small “compressed” spectral features (Fig. 4). Clouds were not expected because at GJ 1214b’s temperature of ~580 K (predicted from a simple calculation of stellar heating and the main elements in planet atmospheres), no condensates were expected at all or to exist in high enough abundance to form blanketing clouds.

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.


Related in: MedlinePlus