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...
WaterRich 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...
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Comparative Study of the Evolution of the Upper Atmospheres of Terrestrial
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
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...