Introduction

Solar forcing affects the planets in the inner solar system in different ways, the most obvious being the solar gravitation force. But there are also other forcing terms affecting the planets solar irradiation and the solar plasma outflow. The solar irradiation, with a spectrum from X-ray to infrared, provides the highest input power to the planetary environment, corresponding to a power between 490-720 W m2 for Mars, with its elliptic orbit, for the Earth 1370 W m2, and 2620 W m2 for Venus....

References

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Habitability of Another WorldIs There a Rock Cycle on Mars that Can Sustain Life

Minerals and rocks are stable only under the conditions at which they form, though kinetics and activation energies permit sustained disequilibrium (if not, diamond rings would vaporise to CO2). Changing these conditions will initiate metamorphism of the rock and its minerals. Therein is disequilibrium, and resources for life. On Earth plate tectonics regularly remodels the face of the planet and is central to the sustained supply of ions and disequilibrium for biogeochemistry. Is there also...

The Present Loss of Volatiles from the Earth Like Planets

Venus Plasma Environment

The volatile content, abundances and states of the Earth-like planets, remains an intriguing issue in planetology. Consider the following alternative theories (1) the present differences in volatile content of the planets is directly related to the accretion process, or (2) the present differences in volatile content is a consequence of the long-term evolution of the planets (gain loss). The first theory assumes an initial accretion differentiation of the planets. The second theory suggests...

Kevin Zahnle Nick Arndt Charles Cockell Alex Halliday Euan Nisbet Franck Selsis Norman H Sleep

Received 16 March 2006 Accepted 17 January 2007 Published online 25 July 2007 Springer Science+Business Media B.V. 2007 Abstract We address the first several hundred million years of Earth's history. The Moon-forming impact left Earth enveloped in a hot silicate atmosphere that cooled and condensed over 1,000 yrs. As it cooled the Earth degassed its volatiles into the atmosphere. It took another 2 Myrs for the magma ocean to freeze at the surface. The cooling rate was determined by atmospheric...

Obliquity Insolation and Atmosphere

Insolation (the flux emitted by the Sun and received at the surface of the planet) and obliquity (the angle between the equator and the orbit plane of a planet) are essential for the understanding of the past climate of the Earth and Mars. The insolations and obliquities of planets are changing with time as gravitational interaction between solar system bodies causes their orbits and spin axes to evolve. The long-term orbital and spin dynamics of the planets depends also on internal planetary...

Sustaining Habitability The Long Term ScaleIs There an Outlook

Is Mars a lesson Does habitability end Will Earth become Mars-like or, for that matter, Venus-like Why has Earth, uniquely, sustained habitability The habitable zone is usually defined as the range of distances from the Sun where liquid water is stable on the planet's surface. This definition has both parochial and operational aspects. The latter in particular focus attention on the kinds of extrasolar planets we might plausibly detect within the horizons of our lives. The conventional...

The History of Water and Climate on Mars

I will discuss the hydrologic history of Mars and what it means for climate on that planet. Although the origin of the valleys and channels on Mars has been debated for over thirty years their origin remains almost as puzzling as it was when they were first observed in 1972 during the Mariner 9 mission. For liquid water to be thermo-dynamically stable, temperatures must exceed 273 K and the atmospheric pressure must exceed 6.1 mbar. For most of the planet the total pressure is...

Variability of the Solar Radiation and Plasma Environment

The Sun is the main source of surface and atmosphere energy for the Earth-like planets, interior energy heat flow playing a negligible role. Without a dependable (stable) star like the Sun, the Earth would not have developed a rich and diverse biosphere, the home to millions of living species. This raises two questions Why only on the Earth, and not also on Mars and Venus Has the Sun always been dependable We focus in this section on the second question, addressing in the following continuing...

Lessons from Earth Contemporary Systems

When addressing the fundamental aspects of life on Earth and its relationship to geology, we have focused on bacteria, which are considered to be a ubiquitous form of life, and exhibit the greatest molecular and metabolic diversity of any life form on Earth (Barns and Nierzwicki-Bauer 1997 Pace 1997 Reysenbach and Shock 2002). Bacteria are active in all surface and subsurface environments (Amy et al. 1992 Bechtel et al. 1996, 1998 Colwell et al. 1997 Lovley and Chapelle 1995 Parkes et al. 1994...

Hadean Geography and Geodynamics

Earth today has a global mean heat flow of 0.086 W m2, which much exceeds heating by radioactive decay 0.040 W m2 . The mismatch is even bigger if the continents aren't included in the accounting. The mismatch shows us that mantle convection is not well described by textbook boundary layer theory, which predicts that heating and cooling are nearly equal. To fix this with plate tectonics requires taking the strength of the plates into account Sleep 2007 . When this is done, the model of plate...

Water Rich Environments on Mars

Volatiles are crucial to habitability see Chap. 4 of this book . Not only are they essential for life, they also shape the enviroment. Although we do not have evidence for a rock cycle driven by plate tectonics, alteration of rocks due to weathering and transportation is common on Mars. The surface geology exhibits giant outflow channels which start fully developed at discrete sources and expand for hundreds of kilometers. e.g. Sharp and Malin 1975 Baker et al. 1992 Carr 1996 Jaumann et al....

The Late Bombardment

A major scientific result of the Apollo program is that the Moon was hit by several 100-km-size asteroids and by hundreds of 10-km-size asteroids ca. 3.9 Ga Wilhelms 1987 . Earth was hit at the same time, and because Earth's effective cross section is 20 times bigger than the Moon's, Earth was hit 20 times as often. Not only was Earth hit by a hundred 100-km asteroids or comets , it was also hit by a dozen bodies bigger than any to hit the Moon. Here we speak of probabilities in lieu of direct...

Key Questions and Needed Observations

It is too late to ask many of the questions surrounding an origin of life on Earth. How exactly, did life originate on Earth How long did it take for life to originate Did life originate before or during the period of late heavy bombardment, and if it originated before the late heavy bombardment, how did it survive However, the question concerning the possible ori-gin s of life elsewhere in our solar system can be addressed. Are there fossilised remains of extant life on Mars Is there...

Thermospheric Heat Balance and Composition Modelling

The main radiation responsible for heating of upper atmospheres and the formation of planetary ionospheres is the solar XUV radiation. The part of the atmosphere where the XUV radiation is absorbed and a substantial fraction of its energy is transformed into heat, leading to a positive temperature gradient dT dz gt 0, is the thermosphere, which extends from about 90 to 210 km on Venus and Mars and from about 90 to 500 km on Earth. In the lower thermosphere convection can play an important role...

Planets Refrenses

Planet Symp. 1988 , pp. 225-231 Y. Abe, T. Matsui, J. Atm. Sci. 45, 3081-3101 1988 Y. Abe, E. Ohtani, T. Okuchi, K. Righter, M. Drake, in Origin of the Earth and Moon, ed. by R.M. Canup, K. Righter University of Arizona Press, Tucson, 2000 , pp. 413-433 F.C. Adams, G. Laughlin, Icarus 150, 151-162 2001 F.C. Adams, D. Hollenbach, G. Laughlin, U. Gorti, Astrophys. J. 611, 360-379 2004 C.B. Agnor, W.R. Ward, Astrophys. J. 567, 579-586 2002 C. Agnor, E. Asphaug,...

Comparative Study of the Evolution of the Upper Atmospheres of Terrestrial Planets

Exospheric Temperature

For a study of the heating of the Earth thermosphere by XUV radiation from the young Sun, we apply our thermospheric model to an atmosphere with the present atmospheric composition and a related heating efficiency for the solar XUV radiation. The heating efficiency of the ionizing solar radiation in the terrestrial thermosphere can be estimated through the analysis of the photoelectron and ion energy production processes and the ways of conversion of the non-thermal energy of the photolysis...

Yuri N Kulikov Helmut Lammer Herbert IM Lichtenegger Thomas Penz Doris Breuer Tilman Spohn Rickard Lundin Helfried K

Received 1 February 2006 Accepted 10 April 2007 Published online 8 June 2007 Springer Science Business Media B.V. 2007 Abstract Because the solar radiation and particle environment plays a major role in all atmospheric processes such as ionization, dissociation, heating of the upper atmospheres, and thermal and non-thermal atmospheric loss processes, the long-time evolution of planetary atmospheres and their water inventories can only be understood within the context of the evolving Sun. We...