[extropy-chat] MARS: Because it is hard

[Robert J. Bradbury]

On Tue, 13 Apr 2004, Mike Lorrey wrote:

> Well, assuming we want to disassemble the planets, but a number of
> people want to remain corporeal in an acceleration gradient, having a
> couple Mars sized bodies orbiting each other would maximize living
> surface, minimize delta v, while giving each other enough tidal stress
> to accurately replicate Earth-style tectonics and resource
> sequestration.

Hmmm... I'm not sure that I compltely understand this statement.
Are you talking about hollow Mars sized bodies?

Here are my assumptions.
- We have the human genome as well as very sophisticated gene
  expression measurement technology.  The entire bone/muscle loss
  problem should be figured out within the next decade.
- An O'Neill structure encases the atmosphere so you don't have
  to worry about losing it due to lack of gravity (which you
  do have to worry about with Mars).
- An O'Neill structure can filter UV exposure.
- An O'Neill structure can be constructed so it actually has more
  radiation shielding than the Earth's atmosphere or certainly the
  Mars atmosphere can provide.
- An O'Neill structure can be moved out of harms way (asteroids, comets,
  GRB) more easily.

There are other possible benefits but those are the ones that come to
mind quickly.

> Such habitats would last a lot longer than some O'Neil style colonies
> in a dark-ages state (could happen) without caretakers looking after
> things (a la Ringworld Engineers).

Ok, if you are going to assume we return to some dark-ages state
I might agree.  *But* it is a lot harder to destroy the information
content on the planet (due to redundancy, variety of storage locations
and forms, etc.) than it was 1000+ years ago.

One could take for example 911.  A huge loss.  But it looks like the
area is going to be back in business within a decade.  As I've mentioned
before (I think) even an all out nuclear war probably would not set
humanity back too far -- too much technology on nuclear submarines
that can probably not be impacted by nuclear weapons.

As MC Hammer once observed -- "Can't touch this".

> Yeah, it 'wastes' tons of resources. Why can't you use a planets
> resource in situ for computation without having to disassemble it? Why
> do you have to disassemble a planet in the first place? With all the
> hyperthermophilic bacteria found many miles deep in recent years, I
> think we need to seriously reconsider our whole rationale for planet
> disassembly in the first place. If worlds have hot cores, those are
> heat sources useful to power computation just as much as a star inside
> a matrioshka brain.

Ok, these are complex questions.  The simple answer is that most of the
matter in the solar system is *not* in a location where it can be best
used.  For example lets say Mars contains a lot of Hematite.  Hematite
has a melting point of ~1800K.  Which means that if you wanted to build
mechanical rod-logic computers out of hematite (which is almost as good
as sapphire -- M.P. 2300 K) you could position them a lot closer to the
sun and still have functional machines.  Now, if you take Anders' Jupiter
Brain design which requires a core of optical fibers then you need to import
a lot of silicon to create glass (M.P. slightly higher than hematite).
Now the carbon (for diamondoid based materials) is mostly locked up
in the outer solar system (as CO/CO2 ice).  So it is going to take a
while to drag it back into the inner solar system.  At the same time
the highest temperature materials (for computers inside the orbit of
Mercury) are probably going to have to be made of titanium carbide
(M.P. ~3400 K).  There is not a great amount of titanium in the
solar system so one is going to have to disassemble everything to
harvest it -- unless one wants to start using energy resources
and transmutation to breed titanium (I'm not opposed to this -- but
I just don't know the tradeoffs involved).

> Why go out, when we can go in?

Well, if one replaced a Mars iron core with a silicon dioxide core
(say to construct a JBrain fiber optic network) it would become
somewhat lighter.  This would only make the retention of an
atmosphere more difficult than it already is.

I have to conclude that the only way to go is completely engineered
environments.

Robert