1:45 PM - 3:15 PM
[O11-P24] Elucidating the 'Faint Young Sun Paradox' in the primitive Martian atmosphere - CO generation by silent discharges -
Keywords:Mars, Planetary weather, Greenhouse effect
[Background and Purpose]
Based on sedimentary topography, hydrous clay minerals, and D/H ratios observed to date, it is thought that liquid water once existed on Noachian (3.7-4.1 billion years ago) Mars (hereafter ‘primitive Mars’), and subsequently dissipated.1) On the other hand, the surface temperature of the planet is estimated to have been -33 to -13[°C] under the conditions of the “Faint Young Sun” (75% of present solar radiation). (1) On the other hand, surface temperatures are estimated to be -33 to -13 [°C] under the conditions of the “Faint Young Sun” (75% of current solar radiation) at that time.
“In response to this discrepancy, there is still no academic theory (in the greenhouse effect approach) that can explain how the atmosphere evolved to its current state that (a) produces the necessary warming and rainfall, (b) has a reliable source of the necessary gases, (c) is sustainable, and (d) is “ 2).
In this study, we reproduced possible chemical reaction processes in the primitive Martian atmosphere (atmospheric composition changes due to atmospheric photodischarge and silent discharge) in the laboratory, and aimed to elucidate the ‘dark sun paradox’ in the primitive Martian atmosphere due to its greenhouse effect.
[Methods]
The following ‘operations’ were performed on 3) H2/CO2 mixtures (hereafter ‘mixtures’ (H2:CO2=2:1[v/v]) that mimic the Noachian Martian atmosphere, and each was analyzed by GC Analysis was performed by GC** for each of them.
1. UV light (mercury halogen lamp/40W:0,10,20,25[min]) irradiation
2. Radiation (b-rays, γ-rays/[42μSv/h]:20[min]) irradiation
3. Radiation (b-rays, γ-rays/[42μSv/h]:60[min]), each with catalyst (Ni, Pb, Al) plates added
4. Vacuum discharge (10,100,1000[sec])
Supplement: 1. and 4. were performed in test tubes (borosilicate glass) and rubber stoppers. 2. and 3. were performed in 500 ml PET bottle containers (polyethylene) with the gas sealed.
**/equipment: GC-TCD, column: activecarbon 30/60, carrier gas: Ar
[Results]
The GC (gas chromatography) results of ‘4. vacuum discharge (1000 [sec])’ on the gas mixture are shown in Figure 1. (In addition to H2, CO2, O2, and N2, a CO peak (time=65[sec]) was observed. This indicates that the H2/CO2 mixture was subjected to a silent discharge (1000[sec]), which probably resulted in the generation of CO due to the dissociation of CO2.
No change in the composition of the gas mixture was observed before or after the other ‘operations’ on the gas mixture.
[The CO production by the discharge can be generalized to natural phenomena such as lightning strikes, etc. Since CO has a lower greenhouse effect than CO2 (Japan Meteorological Agency), this reaction as a whole may have resulted in a negative feedback on the greenhouse effect. However, given that its lifetime in the atmosphere is 2-3 months (4), it is doubtful that CO is present in sustained amounts that actually interfere significantly with the greenhouse effect, unless the frequency of discharges is substantial.
Nevertheless, given that CO is (on Earth) the ‘precursor of tropospheric ozone’(4), it is possible that this reaction had an effect on the weather, if not the greenhouse effect.
[Conclusion]
This study did not resolve the ‘dark sun paradox’ in the primitive Martian atmosphere due to the greenhouse effect, but it does suggest that CO generation may have affected the weather on primitive Mars.
[Acknowledgments]
We thank the Ezofrogs and Associate Professor Mamoru Oshiki, Division of Environmental Engineering, Graduate School of Engineering, Hokkaido University, and Dr. Yukihiro Kamada, Department of Solar and Planetary Space Physics (Planetary Atmospheric Physics), Division of Geophysics, Graduate School of Science, Tohoku University for their support of this research.
Based on sedimentary topography, hydrous clay minerals, and D/H ratios observed to date, it is thought that liquid water once existed on Noachian (3.7-4.1 billion years ago) Mars (hereafter ‘primitive Mars’), and subsequently dissipated.1) On the other hand, the surface temperature of the planet is estimated to have been -33 to -13[°C] under the conditions of the “Faint Young Sun” (75% of present solar radiation). (1) On the other hand, surface temperatures are estimated to be -33 to -13 [°C] under the conditions of the “Faint Young Sun” (75% of current solar radiation) at that time.
“In response to this discrepancy, there is still no academic theory (in the greenhouse effect approach) that can explain how the atmosphere evolved to its current state that (a) produces the necessary warming and rainfall, (b) has a reliable source of the necessary gases, (c) is sustainable, and (d) is “ 2).
In this study, we reproduced possible chemical reaction processes in the primitive Martian atmosphere (atmospheric composition changes due to atmospheric photodischarge and silent discharge) in the laboratory, and aimed to elucidate the ‘dark sun paradox’ in the primitive Martian atmosphere due to its greenhouse effect.
[Methods]
The following ‘operations’ were performed on 3) H2/CO2 mixtures (hereafter ‘mixtures’ (H2:CO2=2:1[v/v]) that mimic the Noachian Martian atmosphere, and each was analyzed by GC Analysis was performed by GC** for each of them.
1. UV light (mercury halogen lamp/40W:0,10,20,25[min]) irradiation
2. Radiation (b-rays, γ-rays/[42μSv/h]:20[min]) irradiation
3. Radiation (b-rays, γ-rays/[42μSv/h]:60[min]), each with catalyst (Ni, Pb, Al) plates added
4. Vacuum discharge (10,100,1000[sec])
Supplement: 1. and 4. were performed in test tubes (borosilicate glass) and rubber stoppers. 2. and 3. were performed in 500 ml PET bottle containers (polyethylene) with the gas sealed.
**/equipment: GC-TCD, column: activecarbon 30/60, carrier gas: Ar
[Results]
The GC (gas chromatography) results of ‘4. vacuum discharge (1000 [sec])’ on the gas mixture are shown in Figure 1. (In addition to H2, CO2, O2, and N2, a CO peak (time=65[sec]) was observed. This indicates that the H2/CO2 mixture was subjected to a silent discharge (1000[sec]), which probably resulted in the generation of CO due to the dissociation of CO2.
No change in the composition of the gas mixture was observed before or after the other ‘operations’ on the gas mixture.
[The CO production by the discharge can be generalized to natural phenomena such as lightning strikes, etc. Since CO has a lower greenhouse effect than CO2 (Japan Meteorological Agency), this reaction as a whole may have resulted in a negative feedback on the greenhouse effect. However, given that its lifetime in the atmosphere is 2-3 months (4), it is doubtful that CO is present in sustained amounts that actually interfere significantly with the greenhouse effect, unless the frequency of discharges is substantial.
Nevertheless, given that CO is (on Earth) the ‘precursor of tropospheric ozone’(4), it is possible that this reaction had an effect on the weather, if not the greenhouse effect.
[Conclusion]
This study did not resolve the ‘dark sun paradox’ in the primitive Martian atmosphere due to the greenhouse effect, but it does suggest that CO generation may have affected the weather on primitive Mars.
[Acknowledgments]
We thank the Ezofrogs and Associate Professor Mamoru Oshiki, Division of Environmental Engineering, Graduate School of Engineering, Hokkaido University, and Dr. Yukihiro Kamada, Department of Solar and Planetary Space Physics (Planetary Atmospheric Physics), Division of Geophysics, Graduate School of Science, Tohoku University for their support of this research.