From: Jeff Davis (jdavis@socketscience.com)
Date: Mon Jan 08 2001 - 19:01:06 MST
In the Fish in Space thread, Ross, Spike, Anders, et al have been
discussing bases on the nearby planets.
Spike Jones wrote:
> "Ross A. Finlayson" wrote:
>
>> Also, on Mercury, as it doesn't spin as it revolves around the Sun
>> but points
>> towards it, half of Mercury is always pointed towards the Sun and
>> the other half
>> dark, like Earth's Moon.
>
> Ross, altho it was once thought to be tidelocked to the sun, it is
> now known that the planet Mercury rotates three times
> for every two times it orbits the Sun (a ``3 - 2 spin-orbit
> resonance'').
> Its too bad, for otherwise we could set up a station on Mercury's
> constant dawn, and have unlimited access to a big heat source
> and a big cold source.
If Mercury had been tidelocked, with one side continuosly facing the sun,
then Ross's 'constant dawn' would have existed in a ring around the planet.
But though it is not tide locked, all is not lost. The same basing
opportunity still exists, but now it's limited to an area around the poles.
>From Nasa's "Welcome to the Planets" page on Mercury,
http://pds.jpl.nasa.gov/planets/welcome/mercury.htm , I found the following:
Obliquity (tilt of axis in degrees)..................0
Orbit inclination (degrees)..........................7
Orbit eccentricity (deviation from circular).........0.206
Mean surface temperature (K).........................452
Maximum surface temperature (K)......................700
Minimum surface temperature (K)......................100
Note that the tilt of the axis is zero degrees. (I interpret this to mean
that the axis is perpendicular to the plane of the orbit. Is that right?)
This would mean that the incident angle of sunlight is constant at any
given lattitude. Logically, the temperature extremes shown above should be
moderated as one moves toward the poles.
At http://www.seds.org/nineplanets/nineplanets/mercury.html, I found the
following comment:
"Amazingly, radar observations of Mercury's north pole (a region not mapped
by Mariner 10)
show evidence of water ice in the protected shadows of some craters."
Water is good.
Regarding Venus, at
http://nova.stanford.edu/projects/mgs/images/t3213.gif
and
http://nova.stanford.edu/projects/mgs/images/p3213.gif
I found temperature and pressure profiles of the Venusian atmosphere.
Check out the graphs.
Right around 50 km altitude, temperature and pressure are around 300K and 1
atm, perfect for human life. Since the atmosphere is 96% CO2, with a
density of 44 gms/mole, an 80/20 N2/O2 atmosphere, at a density of 28.8
gms/mole would be bouyant. You can see where I'm going with this. No need
to put the base on the surface. Tough sledding there. Temperature and
pressure way high. But a dirigible or geodesic sphere works fine, with the
entire interior space habitable.
The atmosphere is clear below the sulphuric acid haze which, coincidently,
starts at around 50 km altitude. (I haven't found any information about
how much visible light, if any, penetrates to, or originates in, the clear
region below the sulphuric acid haze, which tops out at 65 km. Might be
pretty dark. Anyone know the absorbtion characteristics of H2SO4?) Winds
at the top of the atmosphere are pretty fierce, 350 km/hr, but below the
clouds they're mild.
Speaking of the sulphuric acid, it's sounds pretty nasty, but,...perhaps
it's an opportunity in disguise. Seems like it would be a high energy
compound pumped up by the solar radiation. Just as the ocean here on earth
is a giant solar pond, with vast quantities of energy stored in the thermal
gradient, I would guess that the sulphuric-acid-above/carbon-dioxide-below
stratification of the Venusian atmosphere might manifest a similar energy
storage phenomenon with the energy stored in chemical, rather than thermal,
form. Any chemists want to comment on the potential for energy extraction
using sulphuric acid and carbon dioxide? In any event, it seems there are
abundant supplies of C, H, O, and S.
Or perhaps you could actually have a base on the surface. With a floating
component tethered to it, you could extract energy from the thermal gradient.
Well, that's enough for now.
As always,
Best, Jeff Davis
"Everything's hard till you know how to do it."
Ray Charles
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