Re: Right Stuff for the Red Planet

From: Darin Sunley (
Date: Thu Feb 17 2000 - 00:54:32 MST

> James Swayze wrote:
> > A little off the subject but can someone explain to me why people promoting the
> > terraforming of Mars still think it will hold a man made atmosphere despite the
> > believed theory that it lost it's atmosphere in the first place due to it's
> > diminutive size and thus lack of sufficient gravity?

Well, here goes my tri-monthly de-lurk...

In Greg Egan's "Diaspora", a group of post singularity aliens accomplished this
(weighing an atmosphere down) by inserting extra neutrons into the nuclei of
everything on the planet. One of the characters described it as "... they inserted
the changes at the lowest level, beneath the ecosystem."

Would this actually work? In other words, would Terran biochemistry (as distinguished
from any other kind, 'natch :)) continue to work if everything was the next stable
isotope up?

More to the point, can _unmodified_ humans breathe a heavy oxygen/heavy nitrogen
atmosphere without developing lung cancer, or asphyxiation, or similar

Furthermore, what would this do the the half-life of the atmosphere? My knowledge of
gas behavior (does this fall under chemistry, physics, or celestial mechanics? ) is a
little weak (CS degree). Actually, it consists almost entirely of what I've learned
here. Say for example in the simple case, where each particle in the atmosphere is
twice as heavy as it was before. How does this affect atmospheric dissipation rates
due to Brownian motion and/or insufficient gravity?

As a first approximation, a particle at the top of the atmosphere will dissipate if
it exceeds the escape velocity of the planet at that altitude. The average velocity
of all the particles in the atmosphere is simply another way of expressing the
temperature of the atmosphere. Conclusion number one: if the atmosphere was all heavy
atoms, the particles would move less for the same energy input, and would therefore
be colder. (unless I'm wrongly conflating the vibration identified as heat with the
vibration identified as Browning motion. Anybody feel free to jump in :))

So if the rate of dissipation of the atmosphere is proportional to the temperature of
the atmosphere, then doubling the mass of the particles should roughly double the
atmosphere's half-life.

Anybody feel free to tighten this up somewhat?

Darin Sunley

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