Photochemical escape of oxygen from early Mars

Zhao, Jie; Tian, Feng

doi:10.1016/j.icarus.2014.12.032

Cited by 14 publications

(25 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All reactions, apart from DR of CO + and PD of CO, decrease for a higher EUV flux than 10 times the present level. Such a behavior has also been reported by Zhao and Tian [] for DR of

O_{2}^{+}

.…”

Section: Resultssupporting

confidence: 83%

“…From these times until today, the Martian atmosphere was most likely modified by a complex interplay of escape by suprathermal atoms [e.g., Fox , ], sputtering [ Jakosky et al , ], ion escape, impacts, carbonate precipitation, and serpentinization [ Chassefière and Leblanc , ], which led to the present‐day surface pressure. Zhao and Tian [] calculated photochemical escape of oxygen from a Mars atmosphere exposed to 1, 3, 10, and 20 times the present solar EUV flux. They focused on dissociative recombination of

O_{2}^{+}

as source of the energetic oxygen atoms.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms

et al. 2017

View full text Add to dashboard Cite

With a Monte Carlo model we investigate the escape of hot oxygen and carbon from the Martian atmosphere for four points in time in its history corresponding to 1, 3, 10, and 20 times the present solar EUV flux. We study and discuss different sources of hot oxygen and carbon atoms in the thermosphere and their changing importance with the EUV flux. The increase of the production rates due to higher densities resulting from the higher EUV flux competes against the expansion of the thermosphere and corresponding increase in collisions. We find that the escape due to photodissociation increases with increasing EUV level. However, for the escape via some other reactions, e.g., dissociative recombination of O2+, this is only true until the EUV level reaches 10 times the present EUV flux and then the rates start to decrease. Furthermore, our results show that Mars could not have had a dense atmosphere at the end of the Noachian epoch, since such an atmosphere would not have been able to escape until today. In the pre‐Noachian era, most of the magma ocean and volcanic activity‐related outgassed CO2 atmosphere could have been lost thermally until the Noachian epoch, when nonthermal loss processes such as suprathermal atom escape became dominant. Thus, early Mars could have been hot and wet during the pre‐Noachian era with surface CO2 pressures larger than 1 bar during the first 300 Myr after the planet's origin.

show abstract

“…All reactions, apart from DR of CO + and PD of CO, decrease for a higher EUV flux than 10 times the present level. Such a behavior has also been reported by Zhao and Tian [] for DR of

O_{2}^{+}

.…”

Section: Resultssupporting

confidence: 83%

O_{2}^{+}

as source of the energetic oxygen atoms.…”

Section: Introductionmentioning

confidence: 99%

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms

et al. 2017

View full text Add to dashboard Cite

show abstract

“…More recently, Zhao and Tian [] revisited past epoch photochemical escape rates using one‐dimensional Monte Carlo methods. The increase of escape rate with EUV flux was much less than that found by Zhang et al .…”

Section: Implications For Past Mars Atmospheric Lossmentioning

confidence: 99%

“…It makes sense that oxygen escape rates and exospheric densities associated with photochemistry should scale linearly with EUV irradiance. This should remain true if the basic atmospheric composition remains the same for the different solar conditions, but the Zhao and Tian [] model indicated that for EUV irradiances more than 10 times current values the O escape rate actually decreases. This was attributed to an increasing fraction of atomic species rather than molecular species in the upper atmosphere due to increased photodissociation rates.…”

Section: Introductionmentioning

confidence: 99%

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

et al. 2017

View full text Add to dashboard Cite

The evolution of the atmosphere of Mars and the loss of volatiles over the lifetime of the solar system is a key topic in planetary science. An important loss process for atomic species, such as oxygen, is ionospheric photochemical escape. Dissociative recombination of O2+ ions (the major ion species) produces fast oxygen atoms, some of which can escape from the planet. Many theoretical hot O models have been constructed over the years, although a number of uncertainties are present in these models, particularly concerning the elastic cross sections of O atoms with CO2. Recently, the Mars Atmosphere and Volatile Evolution mission has been rapidly improving our understanding of the upper atmosphere and ionosphere of Mars and its interaction with the external environment (e.g., solar wind), allowing a new assessment of this important loss process. The purpose of the current paper is to take a simple analytical approach to the oxygen escape problem in order to (1) study the role that variations in solar radiation or solar wind fluxes could have on escape in a transparent fashion and (2) isolate the effects of uncertainties in oxygen cross sections on the derived oxygen escape rates. In agreement with several more elaborate numerical models, we find that the escape flux is directly proportional to the incident solar extreme ultraviolet irradiance and is inversely proportional to the backscatter elastic cross section. The amount of O lost due to ion transport in the topside ionosphere is found to be about 5–10% of the total.

show abstract

“…Because the collisional cross sections of energetic oxygen atoms are small, photochemical escape of oxygen is a nontrivial process on present-day Mars. If the upper atmosphere of early Noachian Mars was highly expanded, as suggested by Tian et al (2009), it would have been more difficult for the energetic oxygen atoms produced through dissociative recombination reactions in the lower thermosphere to escape, which could have made photochemical escape an inefficient process for oxygen escape on early Mars (Zhao & Tian 2015). Photochemical escape is unlikely to be an efficient escape mechanism on Earth or super-Earths, because the maximum kinetic energy an oxygen atom can obtain from the dissociative recombination reaction of O 2 + is fixed and is substantially lower than the escape energies of planets more massive than Mars.…”

Section: Nonthermal Escapementioning

confidence: 99%

Atmospheric Escape from Solar System Terrestrial Planets and Exoplanets

Tian

2015

Annu. Rev. Earth Planet. Sci.

Self Cite

View full text Add to dashboard Cite

It has been known for decades that atmospheric escape is important for the evolution of terrestrial planets in the Solar System, although exactly how atmospheric escape changes the atmospheres of these bodies is still hotly debated. Rapidly increasing numbers of exoplanet observations provide new targets against which atmospheric escape models are tested. In this review we summarize recent studies related to atmospheric escape from exoplanets. The most important conclusions are that (a) escape can significantly influence the volatile contents of low-mass exoplanets (with mass lower than those of Uranus and Neptune) and the atmosphere and climate evolution histories of Solar System terrestrial planets; (b) models including detailed physics and chemistry in planetary upper atmospheres will be important for the interpretation of existing and future observations of exoplanets; (c) fluid models considering 2D or 3D planetary upper atmospheres and particle models for planetary exospheres will be important not only for comparisons with observations but also for order of magnitude estimates of atmospheric escape rates. Our understanding of how escape shapes planetary atmospheres and influences the climate of low-mass planets can be expected to advance substantially in the coming decade. 15.1

show abstract

Photochemical escape of oxygen from early Mars

Cited by 14 publications

References 24 publications

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

Atmospheric Escape from Solar System Terrestrial Planets and Exoplanets

Contact Info

Product

Resources

About

Photochemical escape of oxygen from early Mars

Cited by 14 publications

References 24 publications

Escape and evolution of Mars's CO2 atmosphere: Influence of suprathermal atoms

Escape and evolution of Mars's CO2 atmosphere: Influence of suprathermal atoms

Hot oxygen escape from Mars: Simple scaling with solar EUV irradiance

Atmospheric Escape from Solar System Terrestrial Planets and Exoplanets

Contact Info

Product

Resources

About

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms

Escape and evolution of Mars's CO₂ atmosphere: Influence of suprathermal atoms