Magnetic Security Blankets

[m_francis]

Meanwhile the Hard Scientists Wonk On

If the Young Sun was 75% fainter than the present sun, as usually thought, how did life ever get started?  Earth should have iced over permanently.  One possible answer comes from study of κ Ceti, which is very like the sun is thought to have been in its early life.  Apparently, its greater activity makes up for

Comments

Young sun, violent sun

[rob_lowrance]

There is another incredible problem for Evolution with regards to the young sun

Re: Young sun, violent sun

[mythusmage]

It is possible the Earth did lose atmosphere to a large solar flare. However, if it did apparently the Earth generated new atmosphere.

It's also more than likely that most of the mega flares never hit the Earth, and very early in Earth career through space there was a lot of crap between us and the sun to attenuate the force of any flare. Life is never as simple as the typical scenario.

Re: Young sun, violent sun

[rob_lowrance]

Earth had to lose its first "atmosphere", if it could be called that: the predominant gasses would have been hydrogen and helium, both of which could and still can easily escape from earth gravity. The current atmosphere we enjoy is most certainly a product of outgassing (e.g., volcanic activity) and biological reactions (oxygen). Even if early earth had been able to hold on to some hydrogen and helium, the absence of a magnetic field (since the iron core had not been differentiated- it takes time) would have made the early atmosphere easy prey for the solar wind. Even if the atmosphere were stripped several times by solar flares, the outgassing of the earth would have no doubt continued. We do still have active volcanoes today

Mars and Venus

[mythusmage]

Not really. Mars, first of all, is too small to be profitably compared to Earth and Venus. If you moved Mars to the orbit of Venus it would still be a cold, dead world. As an old raconteur once said of a small town bar, no atmosphere. Place would warm up some during the day, but then freeze over again at night

[mythusmage]

Two words, carbon dioxide. CO2 levels were much higher back then. Since the start the trend has been towards lower CO2 levels over time, but at the beginnning we had giga tons more carbon dioxide in the air. As a matter of fact, even our current elevated levels are a bare fraction of what the Earth had just 4 billion years ago

Water vapor

[rob_lowrance]

Actually, CO2 is not the most important greenhouse gas. Water vapor is much more effective and much more prevalent than CO2 as a greenhouse gas. However, clouds of water droplets and of ice crystals can have quite different effects. Some cloud types enhance heating while some enhance cooling. Also, the time of day when clouds are present makes an incredible difference in whether heating or cooling predominates

[m_francis]

Makes a neat story. Perhaps the astrophysicists don't know about it. Then, too, at colder temps, more CO2 stays in solution in the oceans and winds up in sediments.

ΔF = α ln(C/C')

So the temperature increase is smaller for higher values of CO2.