Mike--
This is a good point, and will require me to rethink some of what I said
in my previous message about giants.
Certainly the idea is that on Earth plant life unlocked the oxygen, and we
have ways of measuring markers for or "fossil" partial pressure of oxygen
to see when it got here. When that life began here, and the time since to
create that partial pressure, I don't know, and if the length of time it
took it to begin here, and the rate at which oxygenation proceeded here is
representative of other places where life could happen, don't know that
either. Or if there are other mechanisms elsewhere by which it could
proceed.
But in the absence of other ideas, using the Earth yardstick is probably
the only reasonable approach.
Certainly worlds with only a giant star could have a problem developing an
oxygen atmosphere. Some guys say it could happen in the second
(chronological) habitable zone in stars of one stellar mass. And a giant
as part of a multiple could still be worked if it is a far companion or is
one that doesn't grow in a disruptive way, or at least in the billion
years before it gets disruptive.
I wish I had realized this is what you were saying 12-24 hours ago.
So, is this the kind of thinking that is going on in Traveller at large
these days, or only in certain corners?
> Ø That goes back to my assumption that in Traveller we are not really
> thinking about native life. I know that we casually refer to native life
> (and then ignore the animal encounter tables by flying over them in
> air/rafts per recent discussions), but what Traveller is REALLY talking
> about is starfaring races colonizing them in the last 8000 years, or
> Grandfather plopping his experiments down 300,000 years ago, which is
> still an eye-blink in stellar evolution. I assume that all of these
> colonies are bringing their own seed corn and domestic animals with them
>
>
>
> You can bring all of the seed corn and domestic animals to that nearly
> airless rockball you want to, but you still arent going to get a
> breathable
> atmosphere in the next 1000 years.
>
>
>
> You can bring all of the seed corn and domestic animals to that world with
> a
> type A atmosphere, but you arent going to get a breathable atmosphere in
> the next 1000 years.
>
>
>
> Instead, you are going to go to that atmosphere 4-9 world (*maybe* include
> type 2-3, too) and settle there. Cool. I get that. But, where did all of
> that oxygen in the atmosphere come from? Sure, you are terraforming that
> planet by making it more Earth-like. But it was still pretty Earth-like to
> start with. Where did that oxygen come from? It had to come from
> somewhere,
> and has to have something that keeps it there. What was it? Maybe it was
> life that sucks for humans, so you have to bring your own. Maybe it is
> super-primitive life like early plants and lichen and alge. But something
> needs to already be there to make that atmosphere type 4-9 to start with.
> How did the oxygen get there first? Life. And it takes a long time for
> that
> life to develop and change the atmosphere to type 4-9.
>
>
>
> (And that is what Traveller means by terraforming, anyway. You go to a
> world with a breathable or near-breathable atmosphere and a crappy [for
> humans] biosphere and remake the biosphere to suit humans. But that still
> means the world originally had both some kind of human-recognizable
> carbon-based life *and* it had an oxygen-nitrogen atmosphere. Terraforming
> doesnt make the atmosphere; it at best modifies it and changes the
> biosphere.)
>
>
>
> Again, you can put up all of the domes you want. I am not talking about
> those worlds. I am talking about a world with a breathable (or close
> enough)
> type 4-9 atmosphere. No human put that oxygen there. Did the Ancients have
> enough time to put it there? I dunno.
>
>
>
> Mike West
>
>
>
>
>
>
This is a good point, and will require me to rethink some of what I said
in my previous message about giants.
Certainly the idea is that on Earth plant life unlocked the oxygen, and we
have ways of measuring markers for or "fossil" partial pressure of oxygen
to see when it got here. When that life began here, and the time since to
create that partial pressure, I don't know, and if the length of time it
took it to begin here, and the rate at which oxygenation proceeded here is
representative of other places where life could happen, don't know that
either. Or if there are other mechanisms elsewhere by which it could
proceed.
But in the absence of other ideas, using the Earth yardstick is probably
the only reasonable approach.
Certainly worlds with only a giant star could have a problem developing an
oxygen atmosphere. Some guys say it could happen in the second
(chronological) habitable zone in stars of one stellar mass. And a giant
as part of a multiple could still be worked if it is a far companion or is
one that doesn't grow in a disruptive way, or at least in the billion
years before it gets disruptive.
I wish I had realized this is what you were saying 12-24 hours ago.
So, is this the kind of thinking that is going on in Traveller at large
these days, or only in certain corners?
> Ø That goes back to my assumption that in Traveller we are not really
> thinking about native life. I know that we casually refer to native life
> (and then ignore the animal encounter tables by flying over them in
> air/rafts per recent discussions), but what Traveller is REALLY talking
> about is starfaring races colonizing them in the last 8000 years, or
> Grandfather plopping his experiments down 300,000 years ago, which is
> still an eye-blink in stellar evolution. I assume that all of these
> colonies are bringing their own seed corn and domestic animals with them
>
>
>
> You can bring all of the seed corn and domestic animals to that nearly
> airless rockball you want to, but you still arent going to get a
> breathable
> atmosphere in the next 1000 years.
>
>
>
> You can bring all of the seed corn and domestic animals to that world with
> a
> type A atmosphere, but you arent going to get a breathable atmosphere in
> the next 1000 years.
>
>
>
> Instead, you are going to go to that atmosphere 4-9 world (*maybe* include
> type 2-3, too) and settle there. Cool. I get that. But, where did all of
> that oxygen in the atmosphere come from? Sure, you are terraforming that
> planet by making it more Earth-like. But it was still pretty Earth-like to
> start with. Where did that oxygen come from? It had to come from
> somewhere,
> and has to have something that keeps it there. What was it? Maybe it was
> life that sucks for humans, so you have to bring your own. Maybe it is
> super-primitive life like early plants and lichen and alge. But something
> needs to already be there to make that atmosphere type 4-9 to start with.
> How did the oxygen get there first? Life. And it takes a long time for
> that
> life to develop and change the atmosphere to type 4-9.
>
>
>
> (And that is what Traveller means by terraforming, anyway. You go to a
> world with a breathable or near-breathable atmosphere and a crappy [for
> humans] biosphere and remake the biosphere to suit humans. But that still
> means the world originally had both some kind of human-recognizable
> carbon-based life *and* it had an oxygen-nitrogen atmosphere. Terraforming
> doesnt make the atmosphere; it at best modifies it and changes the
> biosphere.)
>
>
>
> Again, you can put up all of the domes you want. I am not talking about
> those worlds. I am talking about a world with a breathable (or close
> enough)
> type 4-9 atmosphere. No human put that oxygen there. Did the Ancients have
> enough time to put it there? I dunno.
>
>
>
> Mike West
>
>
>
>
>
>