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tony1967
2010-Jul-08, 11:49 AM
Hello,
Iíve been watching some programmes which have suggested that as the Sun ages the circumference of the habitable zone will increase. Also they suggest that in the past the sun was 25% cooler than today, but the Earth was kept warm by more greenhouse gases. Can anyone point me to any animations or utilities that show the changes in the habitable zone with time and / or gases in atmosphere with time? Thanks.
Also at what point did Venus leave the habitable zone and at what point will Mars enter? I was thinking that perhaps the gaseous composition of planets has almost as much to do with the habitable zone which is supposed to be the circumference of the zone?
Thanks

swampyankee
2010-Jul-08, 02:04 PM
James Kasting has quite a few of his papers posted on his web site, here (http://www.geosc.psu.edu/~kasting/PersonalPage/Kasting.htm). You can also do a search at www.arXiv.org. Look for "habitable zone."

jfribrg
2010-Jul-09, 03:31 PM
Welcome to BAUT Tony!

eburacum45
2010-Jul-09, 10:02 PM
This page includes a section on the changes in habitable zones for various star types, and has some equations and tables relevant to the subject.
http://www.markelowitz.com/exobiology.htm

It also has quite a lot of other material about habitable zones, although the page itself is a bit haphazard. Hopefully it can give you some useful data.

tony1967
2010-Jul-10, 09:40 AM
Welcome to BAUT Tony!

Thank you it's my third attempt, I've tried to join twice before, registered, then next time I tried to log on and got a "you have be banned, no reason given". After doing nothing, not even posting. I tried to use the contact button but got no reply. Anyway third time lucky :)


I've read the links, my chemistry is poor, but my maths is fairly advanced, but it seems, I think that they still don't really have any solid answers to early cold earth problem, as a great many results seem to contradict themselves.

tony1967
2010-Jul-10, 09:44 AM
One other thing struct me, would there be evidence if earth 3.5+ billion years ago was a snowball? Ice crust with oceans below? Wouldn't this answer the cold early earth paradox? There's no paradox, oit was cold?

dtilque
2010-Jul-11, 08:11 AM
One other thing struct me, would there be evidence if earth 3.5+ billion years ago was a snowball? Ice crust with oceans below? Wouldn't this answer the cold early earth paradox? There's no paradox, oit was cold?

The Earth's albedo was significantly lower during the Archean Eon (3.8 to 2.5 b years ago) thus keeping it warmer. See here (http://www.sciencenews.org/view/generic/id/57810/title/Warmth_in_the_dark_age) for more.

The Earth was also slightly closer to the Sun in that era, which may have helped a little bit. Not sure exactly how much, since the factors that cause the tidal drag (the main cause of the Earth's recession) have not been constant over the history of the Solar System. It will no doubt take some computer modelling to determine exactly how close the Earth was that long ago.

Hernalt
2010-Jul-11, 09:56 AM
"Distant Future of the Sun and Earth Revisited"
http://arxiv.org/abs/0801.4031