Posted to uplink.space.com:


exoscientist
dust
10/25/04 10:42 PM
A closer Mars orbit as the cause of its early "warm, wet period." [re: exoscientist]


In reply to:
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Re: Planetary accretion in the inner Solar System [re: AlexBlackwell]

Thanks for the link. This reminds me of research on the position of planets at their formation and where they wind up:

Moving the Orbits of Planets
http://www.ifa.hawaii.edu/faculty/je...b/migrate.html

This notes that present theories suggest some planets moved outwards while others moved inwards. There is also a paper on the outwards migration of Neptune in the August issue of Icarus.
I wonder if this can explain the "faint-Sun paradox" in regards to the Earth and Mars.
This is the problem that the Sun was supposed to be significantly fainter early in the life of the Solar System but both Earth and Mars show signs of liquid water carved channels at this early time.
This is a big part of the justification for the viewpoint of some Mars scientists that Mars was cold and dry early in its history because theories that propose greenhouse heating under a thicker atmosphere have difficulty getting the required amount of heating.
But perhaps the explanation lies in the possibility that these planets were closer to the Sun early on and that is what allowed them to have the extensive liquid water carved features.



Bob Clark



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A report to be presented to the Fall 2004 AGU meeting will argue that a Mars' orbit closer to the Sun may partially explained how Mars was able to remain warm enough for large scale water carved features to be formed early in its history:

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0800h
AN: P21A-0211
TI: Mars Orbit and Temperature: Why and When an Early wet Mars
AU: * Leubner, I H
EM: ileubner@crystallizationcon.com
AF: Rochester Institute for Fundamental Research, 35 Hillcrest Drive, Penfield, NY 14526 United States
AB: It is the intent of this work to present a model which predicts the time when liquid water was present on Mars. Experimental evidence indicates that liquid water existed on the planet Mars at 2.9 - 3.4 billion years ago, when Mars was considered to be cold. A model is presented that predicts Mars orbit and temperature variations based on solar radiative and non-radiative (solar wind) mass losses which affect planetary orbits. Mars orbits are predicted between 198 and 206 million Km at its formation five billion years ago vs. presently 228 million Km. The correlation between the solar (radiative) constant and planetary orbit estimates the transition from liquid water to ice (273K) to have occurred at about 3.4-3.8 billion years before the present time, which is in good agreement with the experimental estimate (2.9 - 3.4 Byr). Additional effects that are expected to extend higher Mars surface temperatures closer to the present are discussed. Examples are the planetary cooling rate after formation and effects due to hothouse gases, like carbon dioxide and water vapor, and effects dependent on variations in solar volume.

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These are non-peer reviewed abstracts of course.


Bob Clark

there have been ideas before that suggested that another planet Venus, may have experieced planetry migrations

nice article