Space/Science — HabitableZone

Space/Science » in reply to Re: Johannes, start here... Thanks again

Johannes...

Please clarify your thought processes and ask coherent questions without all the extraneous stuff. I literally cannot see where you are going (other than to advise you to refer to the original form of each item, so in the case of the planetary science course you quote, the powerpoint is better than the html translation, especially as regards suffixes and exponents in equations.

Use a bit of common sense, too. If we're looking at whether atmospheres are stable for millions of years or not, a few % difference in g between equator and pole is irrelevant (it only determines where the bulk of the escape occurs). To quote data to 7 significant figures is a sign that you don't understand what the numbers mean.

Re-read the bit about Jeans escape and the evaporation timescale of the Earth (or actually it's hydrogen). This is quoted as 10^15 years (one million billion years).

Jeans escape depends on kinetic energy, which depends on temperature. (it actually depends on the energy of the fastest fraction of the molecules, since these are the ones that escape)

Try this reference

The equations are difficult, and complex. The relationship to temperature, T is non-trivial, but to a first approximation the escape rate scales as something like T^2. So, for the Earth, to reduce the timescale for ocean evaporation from one million billion years to a "mere" billion years (which would have seen the oceans lost before life adapted to land), you must increase temperature by a factor of 1000

So a surface temperature of 273,000 K would be required to "boil-off" the atmosphere.

Since this is hotter than a nuclear reactor core, your worries appear groundless...

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