Fluctuations of CO2, O2, O3, and CH4 in atmospheres

Regular oscillations of atmospheric gases e.g. seasonal fluctuations of CO2, O2, O3, and CH4 are solely a product of biological activity and thus can be regarded as biosignatures.
Created at: 
2020-04-20
  Updated at: 
2020-04-21
Curator:
Pengxiao Xu   Subscribe ...

Background

Biological Prevalence

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Seasonal oscillation of CO2 is a result of plant activity and can be a biosignature.

eSeasonal oscillation of atmospheric CO2 found on Earth mainly due to activity of land plants.
Earth

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Some abiotic processes can also cause seasonal changes in CO2 level.

eCO2 level in Mars’ atmosphere changes seasonally, primarily due to the exchange between atmosphere and Mars’s seasonal polar cap.
Earth

eSome abiotic processes can result in regional CO2 variation on time scales shorter than one year.
Earth

eCO2 oscillation caused by land plants might be offset by orbital effect, which is possible to be a false negative.
Exoplanets Earth

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Seasonal oscillation of O2 is caused by plant activity.

eAtmospheric molecular oxygen level changes seasonally in both hemispheres, due to the biological activity.
Earth

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Abiotic processes can also lead to seasonal variation in atmospheric O2 level.

eSeasonal variations in atmospheric O2/N2 ratio that is not related to biological activity has been reported in both hemispheres on Earth.
Earth

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Seasonal variation in O3 is caused by plant activity and is a biosignature.

eOzone varies significantly between wet seasons and dry seasons in Amazonia because of rainforest activity.
Earth

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Seasonal variations in CH4 due to plant activity can be a biosignature.

eSeasonal variations of CH4 can be an indicator of temporal changes in biological methanogenesis.
Mars

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Changes in CH4 level in the Earth’s atmosphere is mainly caused by abiotic processes.

eAtmospheric CH4 level is mainly controlled by its reaction with OH which increases in summer, due to higher surface temperatures.
Earth

Abiotic Prevalence

Biotic Signal Strength

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These biosignature gases especially CO2 and CH4 are spectrally active and detectable on an exoplanet.

eEvidence: Researchers have detected CH4 and CO2 in the atmosphere of an exoplanet.

Abiotic Signal Strength