From: "Ed Minchau"
To:
Sent: Monday, February 05, 2001 7:00 AM
Subject: [spacesettlers] Re: More Venus terraforming...Go Deep

How about this instead? Put up a big reflector in the L2 point of
Jupiter. Set it to reflect incoming sunlight on Europa, start a deep
melt...

In some ways, terraforming the icy Galilean moons is much easier than doing
the same with Venus. You "just" have to build the absurdly huge mirrors at
appropriate locations, melt the moons until uncover their subglacial oceans
and then seed them with adequate microorganisms to transform their brand new
atmospheres in something breathable. Then you would have nice oceanic worlds
and could colonize them using Savage's floating cities approach.

The plan above was outlined in "Padres de Contato", a science fiction book
from a Brazilian author, Jorge Luiz Calife. (Although Calife used
fusion-powered artificial suns instead of mirrors, in his book.) Of course
there is also the Galilean terraformation version used by K.S. Robinson (in
"Blue Mars") and Arthur Clarke (in "3001"): to put enough sunlight to raise
the temperature just to the melting point in the equator and leave the rest
of the world in deep freeze. I don't like this plan, perhaps because I'm
Brazilian and anything below 10 C (or 50 F) is unbearably cold for me. (In
fact, when I visited the United States during the winter, my hopes that
someday Humanity would colonize space were boosted: after all, there were
already people living in places that *I* consider uninhabitable! ;-)

:) ed
[snikt]

Lucio

--- In spacesettlers@y..., "Dr. Omni" wrote:
> to put enough sunlight to raise
> the temperature just to the melting point in the equator and leave
the rest
> of the world in deep freeze. I don't like this plan, perhaps
because I'm
> Brazilian and anything below 10 C (or 50 F) is unbearably cold for
me. (In
> fact, when I visited the United States during the winter, my hopes
that
> someday Humanity would colonize space were boosted: after all,
there were
> already people living in places that *I* consider uninhabitable! ;-)
>
> Lucio

Leaving the polar caps icy would reduce the effects of tidal waves.
Jupiter's tidal forces are incredible; they cause Io to erupt
continuously.

I live in Calgary, Canada. I just looked at the thermometer
outside: -21C at 6 am, and the sun won't be up for a few hours yet.
I have been outside in temperatures as low as -47C without the wind
chill, and temperatures as low as -86C with the wind chill (by the
way, even minor frostbite sucks). Ten degrees is a pleasant spring
day, I wouldn't even wear a jacket. 35C is unbearably hot.

I guess Einstein was right: everything IS relative.

:) ed

Does anyone realize that the Jovian satellites don't have enough
gravity to hold an atmospere? There wouldn't be a liquid ocean,
because it would immediately evaporate and be lost to space, and
Jupiter orbit. There isn't enough material on all of the planets
combined to produce a gas torus effect, so by melting the ice surface,
you will effectively boil off the water.

Bill

--- In spacesettlers@y..., "Ed Minchau" wrote:
> --- In spacesettlers@y..., "Dr. Omni" wrote:
> > to put enough sunlight to raise
> > the temperature just to the melting point in the equator and leave
> the rest
> > of the world in deep freeze. I don't like this plan, perhaps
> because I'm
> > Brazilian and anything below 10 C (or 50 F) is unbearably cold for
> me. (In
> > fact, when I visited the United States during the winter, my hopes
> that
> > someday Humanity would colonize space were boosted: after all,
> there were
> > already people living in places that *I* consider uninhabitable!
;-)

--- In spacesettlers@y..., "Bill" wrote:
>
> Does anyone realize that the Jovian satellites don't have enough
> gravity to hold an atmospere? There wouldn't be a liquid ocean,
> because it would immediately evaporate and be lost to space, and
> Jupiter orbit. There isn't enough material on all of the planets
> combined to produce a gas torus effect, so by melting the ice
surface,
> you will effectively boil off the water.
>

Good point. Perhaps a deep thaw on Europa, leaving the surface
relatively intact? If we are going to have undersea colonies on
earth, maybe we can build underice colonies as well.

Instead of a giant reflector, you would need to convert much of the
incoming radiation into microwaves; this requires a big solar panel
and a maser. With it you could heat Europa from the seabed up.

:) ed

From: "Bill"
To:
Sent: Friday, February 09, 2001 3:38 PM
Subject: [spacesettlers] Re: Galilean terraformation

Does anyone realize that the Jovian satellites don't have enough
gravity to hold an atmospere? There wouldn't be a liquid ocean,
because it would immediately evaporate and be lost to space, and
Jupiter orbit. There isn't enough material on all of the planets
combined to produce a gas torus effect, so by melting the ice surface,
you will effectively boil off the water.

Not exactly. Using E=3/2kT, where K is the Boltzmann Constant, one can
calculate that the average kinetic energy of a molecule at 15 C (Earth's
average temperature) is 5.96x10^-21. Since a water molecule has a mass of
about 3.00x10^-26, then the average velocity of a water vapor molecule at
that temperature would be (from Ec=mv^2/2) just 630 m/s.

Well, the escape velocity for Ganymede is 2740 m/s; 2450 m/s for Callisto;
and 2020 m/s for Europa. (Data from http://www.solarviews.com/ .) As you can
see, it is far above than the velocity of our molecule.

Of course that is an *average* velocity: there will be molecules that will
be faster, and other ones will be slower. Anyhow, most of them will be
trapped in the moon's gravity well. Immediately after you begin your heating
process, it is true that, for an observer in the surface of any of those icy
moons, the water vapor would seems to be dispersing completely in space, but
in fact most of it would be dispersing (and staying) into a sphere with many
millions of cubic kilometers around the moon. After some time (decades?
centuries? millennia? I don't know, and I'm too lazy at his moment to do
another napkin calculation... ;-), however, the cumulative effect of all
those molecules would manifest as a thin atmosphere; given more time, that
atmosphere could be thick enough to allow liquid water, and then we would
have our long-sought oceans.

Of course the atmospheric loss of those moons - the volume of molecules fast
enough to leave the atmosphere - would be huge compared to the same rate for
Earth. But the volume of vapor and water would be so huge that, for a human
civilization, the time necessary for all the water in a Galilean moon to
dissipate in space would be an eternity, in practice.

So, I would rephrase what you said - "the Jovian satellites don't have
enough gravity to hold an atmosphere" - to "the Galilean satellites don't
have enough gravity to hold an atmosphere *during geological time spans*".
But human civilizations don't live through a geological lifespan, anyway...
And so I still think that terraformation of the Galilean moons is
theoretically possible.

Bill

Lucio

I will have to do the calculations, but I had calculated the
equilibrium pressure in a gas torus around Europa to be about 2%
of the earth atmospheric pressure, if there was enough material on
Europa, which there wasn't.

Yes technically this is an atmosphere, but for practical purposes
it is a vacuum to us.

I'll dig up the calculations.

Bill

>
> Does anyone realize that the Jovian satellites don't have enough
> gravity to hold an atmospere? There wouldn't be a liquid ocean,
> because it would immediately evaporate and be lost to space, and
> Jupiter orbit. There isn't enough material on all of the planets
> combined to produce a gas torus effect, so by melting the ice
surface,
> you will effectively boil off the water.
>
> Not exactly. Using E=3/2kT, where K is the Boltzmann Constant, one
can
> calculate that the average kinetic energy of a molecule at 15 C
(Earth's
> average temperature) is 5.96x10^-21. Since a water molecule has a
mass of
> about 3.00x10^-26, then the average velocity of a water vapor
molecule at
> that temperature would be (from Ec=mv^2/2) just 630 m/s.
>
> Well, the escape velocity for Ganymede is 2740 m/s; 2450 m/s for
Callisto;
> and 2020 m/s for Europa. (Data from http://www.solarviews.com/ .) As
you can
> see, it is far above than the velocity of our molecule.
>
> Of course that is an *average* velocity: there will be molecules
that will
> be faster, and other ones will be slower. Anyhow, most of them will
be
> trapped in the moon's gravity well. Immediately after you begin your
heating
> process, it is true that, for an observer in the surface of any of
those icy
> moons, the water vapor would seems to be dispersing completely in
space, but
> in fact most of it would be dispersing (and staying) into a sphere
with many
> millions of cubic kilometers around the moon. After some time
(decades?
> centuries? millennia? I don't know, and I'm too lazy at his moment
to do
> another napkin calculation... ;-), however, the cumulative effect of
all
> those molecules would manifest as a thin atmosphere; given more
time, that
> atmosphere could be thick enough to allow liquid water, and then we
would
> have our long-sought oceans.
>
> Of course the atmospheric loss of those moons - the volume of
molecules fast
> enough to leave the atmosphere - would be huge compared to the same
rate for
> Earth. But the volume of vapor and water would be so huge that, for
a human
> civilization, the time necessary for all the water in a Galilean
moon to
> dissipate in space would be an eternity, in practice.
>
> So, I would rephrase what you said - "the Jovian satellites don't
have
> enough gravity to hold an atmosphere" - to "the Galilean satellites
don't
> have enough gravity to hold an atmosphere *during geological time
spans*".
> But human civilizations don't live through a geological lifespan,
anyway...

Please do it - I'm by no way sure about my calculations and it would be nice
to compare them other ones made independently. Also, I used the simplest
kind of calculation possible: just using average velocity and stuff. But
that is obviously a poor modeling of reality, since I'm not taking into
account the fact that the slow molecules can eventually gain momentum and
get lost in space.

I remember about seeing a long time ago an equation for atmospheric
dissipation - it was used in a website for demonstrating that the 51 Pegasi
planet is more likely a gas giant, despite being so close to its star. I'll
look for that again and try to apply the equation to the case of the
Galilean moons.

Thanks in advance,

Lucio

From: "Bill"
To:
Sent: tera-feira, 13 de fevereiro de 2001 12:38
Subject: [spacesettlers] Re: Galilean terraformation

I will have to do the calculations, but I had calculated the
equilibrium pressure in a gas torus around Europa to be about 2%
of the earth atmospheric pressure, if there was enough material on
Europa, which there wasn't.

Yes technically this is an atmosphere, but for practical purposes
it is a vacuum to us.

I'll dig up the calculations.

Bill

[snikt]