Re: Hottest and coldest habitable worlds...

Johnny1a wrote:

This is a question that doesn't lend itself to precise formulation,
but consider the 'Golden Age' concepts of Venus and Mars, i.e. the
swampy jungle tropical Venus and desert-and-canals Mars. Both
fictional worlds are 'habitable' in that a human being can exist in
their surface environments without life-support equipment, s/he might
not be comfortable, but s/he can live, at least on some parts of the
surface.

(It might get too cold at night on Golden Mars, or there might be
parts of Golden Venus that are _too_ hot or high-pressure to survive,
but in each case there are parts of the surface where an unaided Human
can survive. There are spots on Earth where an unaided Human can't
survive, too.)

Certainly Golden Mars/Venus are gardenworlds compared to any real
planets in the Solar System except Earth.

So...in the real universe, just how much like Golden Venus could a
planet be before conditions ran away and turned it into something
resembling Real Venus? Likewise, how cold can an Earth-like world be
(and how globaly dry) before a survivable environment can't exist?

Another way to express this question: had conditions been different,
_could_ Golden Venus and/or Golden Mars have existed, under the laws
of nature as we know them? In some alternative history with the same
physics?

I expressed this in a set of stories that never got written - set in an F1
system that had one superjovian where the other star should have happened,
and two binary planets absorbing the slack in the rather wide temperate
zone:
one pair of planets, the closer to the sun, was light - approx .4 E and .7
E, and consequently couldn't hold on to much H2O.
the other pair, much further out from the sun, was much more massive -
approx 1.8 E and 2.3 E,, and consequently full of H2O. One was an ocean
planet, the other was an almost-ocean planet.

The key variable for the Golden Venus and Golden Mars is of course water.
And the truism is that the lighter the planet, the less water it will have.
so a putative "Golden Venus" is going to be more massive than a
putative "Gold Mars".

(We can vary the mass or other vital stats as long as we stay with
known phsyics and chemistry.)


Shermanlee

.

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