Terraforming mars in a short time

(Henry Spencer) wrote in message ...
In article , Frank Scrooby wrote:
I personally haven't worked out the physics but Martyn Fogg, a very smart
gentleman who has written a very impressive book on terraforming, calculated
the figures that I mentioned i.e. that Mars has CO2 reserves for a 2 Earth
Atmosphere equivalent atmosphere...

Careful here. Nobody is *sure* of that. Martyn Fogg is a sharp guy, but
such calculations inevitably rest on assumptions which are not much better
than guesses right now.

My hand waving is as good as anybody elses, generates heat too.

(Henry Spencer) wrote in message ...
In article , Frank Scrooby wrote:
I personally haven't worked out the physics but Martyn Fogg, a very smart
gentleman who has written a very impressive book on terraforming, calculated
the figures that I mentioned i.e. that Mars has CO2 reserves for a 2 Earth
Atmosphere equivalent atmosphere...

Careful here. Nobody is *sure* of that. Martyn Fogg is a sharp guy, but
such calculations inevitably rest on assumptions which are not much better
than guesses right now.

My hand waving is as good as anybody elses, generates heat too.

Parallax wrote:

(snip) This uses
only the material of the comet (assumed .2 gm/cm3)

A fifth of the density of water? That seems low.

--
Hop David
http://clowder.net/hop/index.html

Parallax wrote:

I decided to use comets because the energy requirement to heat the
Martian CO2 to produce an atmosphere might be unreasonable while the
kinetic energy of a comet is there for free. Furthermore, comets seem
to have some nitrogen in them (Methyl Cyanide).

For my very rough calculation, I used the minimum density for Comet
Encke of .16 gm/cm3 I found on the web and arbitrarily decided that .2
was better.

Did some Googling. . . If the comets are fluffly snowball .1 gram/cm^3
but if sheets of dirt and ice up to 2.0 gram/cm^3.

Knowing the size and rotation of Encke they deduced if it were less than
..16 gm/cm^3 it'd fly apart. So this is a _minimum_. Encke could well be
more dense.


I read in National Geographic (It came yesterday) that
Mars surface atmosphere is about 1% density of earths which I once
calculated at about .016 gm/cm3 (once again, could easily be wrong and
based on my poor memory).

Air here is about .0013 gram/cm^3, I believe.

Picked an atmospheric height of 50 Km for a
fictitious atmosphere based on something I read about the heatshield
on Spirit and decided the simplest model was uniform density with
height cuz this would overestimate the number of comets, calculaated
this atmospheric volume and got this number.

By my calcs a 50 km atmospheric shell on Mars would have 7.36E24 cubic
centimeter volume. It would take 9.5E21 grams to give this volume
atmospheric density.

I believe 2600 comets of radius 20 kilometers & specific gravity .2
would be 1.75E22 grams or about twice as much as you'd need.

Although I believe comets will often be more than .2 density and even
if Mars troposphere goes up 50 km, not all of it will be uniform density.
I'd expect half the mass to be in the bottom 10 kilometers or so.

--
Hop David
http://clowder.net/hop/index.html

Marvin wrote:
(Parallax) wrote in
om:


A "side of the envelope calculation" (even more cursory than back of
the envelope), gives about 2600 comets each about 20 Km diameter to
raise the atmospheric pressure from .01 earth to .1 earth. This uses
only the material of the comet (assumed .2 gm/cm3) and does not
account for any greenhouse effect that will cause more CO2 to go into
the Mars atmosphere. It might be considerably fewer. It also does
not account for CO2 and water vapor produced by cometary impact.



Owch.
Whacking that into Mars, on cometary type trajectories.
Impact at about 39km/sec
Total kinetic energy released = 1.27 * 10^24 joules
== 426 *Million* Megatons equivalent

If you send them down so that they're traveling parallel with Mars at
their perihelion it'll be 10 km/sec + martian escape velocity of 5 km/sec.



--
Hop David
http://clowder.net/hop/index.html

JRS: In article , seen in
news:sci.space.policy, Hop David hopspageHATESSPAaMmM@tabletoptelephone
..com posted at Sat, 10 Jan 2004 01:20:35 :-

Although I believe comets will often be more than .2 density and even
if Mars troposphere goes up 50 km, not all of it will be uniform density.
I'd expect half the mass to be in the bottom 10 kilometers or so.

Better to work from the pressure, which is well enough known, and the
local gravity, which directly gives the mass above each unit of area;
then multiply by the area. Use the pressure at an average ground
height, of course.

Corrections for change of gravity with height will be unimportant; but
given that scale height here is about 5 km, Mars g is 0.38 (?) of ours,
and Mars is colder, use the value of g at a height of 10 km as a better
average.

--
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