Warming Early Mars with Carbon Dioxide Clouds That Scatter Infrared Radiation

Forget, F.; Pierrehumbert, Raymond T.

doi:10.1126/science.278.5341.1273

Cited by 426 publications

(414 citation statements)

References 22 publications

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“…As calculated in the previous section, the abundance of carbonates in meteorites, if extrapolated globally, suggests the presence of no more than ∼0.25 bar of CO 2 in the upper kilometer. Such CO 2 , if released, would not be sufficient to raise the global mean surface temperature to above freezing (Forget and Pierrehumbert, 1997) although it might contribute to seasonal tropical warming above freezing in combination with obliquity cycles (Haberle et al, 2000). More concentrated subsurface deposits of carbonate sediments are needed to explain sequestration of a thick, early martian atmosphere.…”

Section: Carbonates In the Martian Crust And Atmospheric Loss Processesmentioning

confidence: 99%

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Bridges

Catling

Saxton

et al. 2001

Space Science Reviews

218

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Abstract. The SNC (Shergotty-Nakhla-Chassigny) meteorites have recorded interactions between martian crustal fluids and the parent igneous rocks. The resultant secondary minerals -which comprise up to ~ 1 vol.% of the meteorites -provide information about the timing and nature of hydrous activity and atmospheric processes on Mars. We suggest that the most plausible models for secondary mineral formation involve the evaporation of low temperature (25-150 o C) brines. This is consistent with the simple mineralogy of these assemblages -Fe-Mg-Ca carbonates, anhydrite, gypsum, halite, clays -and the chemical fractionation of Ca-to Mg-rich carbonate in ALH84001 'rosettes'. Longer-lived, and higher temperature, hydrothermal systems would have caused more silicate alteration than is seen and probably more complex mineral assemblages. Experimental and phase equilibria data on carbonate compositions similar to those present in the SNCs imply low temperatures of formation with cooling taking place over a short period of time (e.g. days). The ALH84001 carbonate also probably shows the effects of partial vapourisation and dehydration related to an impact event postdating the initial precipitation. This shock event may have led to the formation of sulphide and some magnetite in the Fe-rich outer parts of the rosettes.Radiometric dating (K-Ar, Rb-Sr) of the secondary mineral assemblages in one of the nakhlites (Lafayette) suggests that they formed between 0 and 670 Ma, and certainly long after the crystallisation of the host igneous rocks. Crystallisation of ALH84001 carbonate took place 0.5 Ga after the parent rock. These age ranges and the other research on these assemblages suggest that environmental conditions conducive to near-surface liquid water have been present on Mars periodically over the last ~1 Ga. This fluid activity cannot have been continuous over geological time because in that case much more silicate alteration would have taken place in the meteorite parent rocks and the soluble salts would probably not have been preserved.The secondary minerals could have been precipitated from brines with seawater-like composition, high bicarbonate contents and a weakly acidic nature. The co-existence of siderite (Fe-carbonate) and clays in the nakhlites suggests that the pCO 2 level in equilibrium with the parent brine may have been 50 mbar or more. The brines could have originated as flood waters which percolated through the top few hundred metres of the crust, releasing cations from the surrounding parent rocks. There is no spectroscopic or photographic evidence for extensive evaporite deposits on the current martian surface but some salt precipitation through solute concentration must have occurred as floodwaters associated with many of the martian channels ponded in low-lying areas. The high sulphur and chlorine concentrations of the martian soil have most likely resulted from aeolian redistribution of such aqueously-deposited salts and from reaction of the martian surface with volcanic acid volatiles. However, the SNC...

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Section: Carbonates In the Martian Crust And Atmospheric Loss Processesmentioning

confidence: 99%

Untitled

Bridges

Catling

Saxton

et al. 2001

Space Science Reviews

218

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“…One eliminates the CO2 clouds by invoking heating of the atmosphere due to the absorption of ultraviolet radiation by small amounts of SO2 [Yung et al, 1997]. The other exploits the presence of CO2 clouds by showing that they can reflect infrared radiation back to the surface [Forget and Pierrehumbert, 1997]. While each mechanism is promising, more detailed 3-D modeling is needed to better assess their potential for warming early Mars.…”

Section: Discussionmentioning

confidence: 99%

Early Mars Climate Models

Haberle¹

1998

J. Geophys. Res.

122

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Abstract.It is often stated that Mars and Earth had similar environmental conditions early in their history and that life might therefore have originated on Mars as well as on Earth. However, the atmospheric conditions required to produce and sustain a warm, wet climate on early Mars remain uncertain. State-of-the-art greenhouse models predict global mean surface temperatures early in Mars' history that differ little from today's, unless special conditions are invoked. The greatest difficulty the models have is coping with a faint early Sun. IntroductionIn spite of the failure of the Viking landers to detect life of any kind, Mars remains a high-priority target for exobiological investigations. The reason for this is the possibility that Mars and Earth experienced similar climatic conditions early in their history and that because life started on Earth, it might also have started on Mars. Then as the planets evolved, life flourished on Earth but became extinct on Mars. Certainly, the evidence for possible Martian microbes found in ALH84001 has heightened interest in this scenario [McKay et al., 1996]. If confirmed, it would rank as one of the most significant discoveries in the history of civilization.However, in spite of a great deal of work on the subject, our understanding of early Mars' climate history remains fuzzy. While the evidence for flowing liquid water in Mars' ancient terrains is compelling, a widely accepted mechanism for producing warm, wet conditions through climate change has yet to emerge. The main difficulty is dealing with the faint young Sun and finding a way to generate and sustain an atmosphere capable of producing a significant greenhouse effect.As will become evident, our thinking about how the early Mars atmosphere could have produced a significant greenhouse effect has alternated between views concluding it could have, and those concluding it could not have. It is the classic modus operandi of scientific thinking; theories are proposed, scrutinized, revised, or abandoned altogether.The purpose of this paper is to review the history of this fascinating subject to provide a context for where we presently stand on this issue. The paper draws heavily from related reviews by Cart [1996], Squyres and Kasting [1994], and Fanale et al. [1992] but emphasizes the climate models themselves and the processes they represent. The presentation is chronological, so that the reader can follow how our thinking has evolved with time. BackgroundAt the turn of the century the possibility that Mars had liquid water flowing on its surface was popularized in the writings of Percival Lowell, who envisioned vast canal systems constructed by intelligent beings struggling to survive on a dying planet. This romantic view of the red planet was convincingly dispelled This paper is not subject to U.S. copyright. Published in 1998 by the American Geophysical Union. Paper number 98JE01396.in the 1960s by the early Mariner spacecraft, which found no evidence for canals and, more important, near-surface temperatures and...

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“…Using the boundaries of the HZ as defined by Kasting et al (1993), the size of this zone is limited to a small region, depending on the spectral type and the age of the host-star. Taking into account the studies by Forget et al (1997) or Mischna et al (2000), we get a potentially larger HZ for a sun-like star. However, the planet's eccentricity has to be small enough if we require that the whole orbit of a planet is in the HZ.…”

Section: Binary Star Systems and Habitable Planets?mentioning

confidence: 99%

Dynamical Stability and Habitability of Extra-Solar Planets

Pilat-Lohinger¹

2011

Proc. IAU

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Abstract.Observations of about 60 binary star systems hosting exoplanets indicate the necessity of stability studies of planetary motion in such multi-stellar systems. For wide binary systems with separations between hundreds and thousands of AU, the results from single-star systems may be applicable but, in tight double stars systems, we have to take the stellar interactions into account which influences the planetary motion significantly. This review discusses the different types of planetary motion in double stars and the stability of the planets for different binary configurations. An application to the most famous tight binary system (γ Cephei) is also shown. Finally, we analyze the habitability from the dynamical point of view in such systems, where we discuss the motion of terrestrial-like planets in the so-called habitable zone.

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Warming Early Mars with Carbon Dioxide Clouds That Scatter Infrared Radiation

Cited by 426 publications

References 22 publications

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Early Mars Climate Models

Dynamical Stability and Habitability of Extra-Solar Planets

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