Inhabitable Planets Too Close Together?

SWM wrote:However, an empty planet also imposes significant hurdles for colonization. A planet without life will not have oxygen. An oxygen atmosphere is unstable, and cannot last without being replenished. Free oxygen will oxidize numerous materials on a planet, and will disappear on less than geological timescales. So colonizing a planet without any life means a lot of terraforming, to create an oxygen atmosphere. It would take at least several generations to have a breathable atmosphere. It appears that very few planets without life have been colonized in the Honorverse.

not necessarily, but it wouldn’t have an Oxygen cycle. Still that’s not a bad thing. The rich CO2 atmosphere would give Terran plants a lot of help in taking hold. Soil nutrients would have to be added to the soil and probably the water but the plants/algae would take care of starting the O2/CO2 cycle.

There’s no real info on which planets were or weren’t terraformed except those of Manticore & Grayson.

MAD-4A wrote:

SWM wrote:However, an empty planet also imposes significant hurdles for colonization. A planet without life will not have oxygen. An oxygen atmosphere is unstable, and cannot last without being replenished. Free oxygen will oxidize numerous materials on a planet, and will disappear on less than geological timescales. So colonizing a planet without any life means a lot of terraforming, to create an oxygen atmosphere. It would take at least several generations to have a breathable atmosphere. It appears that very few planets without life have been colonized in the Honorverse.

not necessarily, but it wouldn’t have an Oxygen cycle. Still that’s not a bad thing. The rich CO2 atmosphere would give Terran plants a lot of help in taking hold. Soil nutrients would have to be added to the soil and probably the water but the plants/algae would take care of starting the O2/CO2 cycle.

There’s no real info on which planets were or weren’t terraformed except those of Manticore & Grayson.

I'm not sure exactly what your "not necessarily" is specifically referring to. If you mean to say that a planet without life could have an oxygen atmosphere, is not true. If all life on Earth suddenly died, the oxygen in the atmosphere would be quickly (on the geological scale) converted into metallic oxides, CO, CO2, nitrous oxides, and various other oxides. When the atmosphere stabilized, there would be essentially no free oxygen. The only reason there is oxygen in our atmosphere is because of living organisms. Free oxygen in an atmosphere is a near-certain signature of life, and having a sufficient partial pressure of oxygen for humans to breath is a certain signature of life.

If you are talking about using plants (algaes are the ones usually suggested in the literature) to create an oxygen atmosphere from a CO2 atmosphere, then you are talking terraforming. And I already said that a planet like that would require significant terraforming. It would take many generations to generate a breathable atmosphere that way.

MAD-4A wrote:There’s no real info on which planets were or weren’t terraformed except those of Manticore & Grayson.

While there is no real info on which planets were or weren't terraformed, the text strongly suggests that almost every planet other than near-Earth analogues like Manticore and Sphinx required at least some terraforming.

At the same time, the text also suggests that colony planets were almost always chosen because they already had life. That greatly reduces the amount of terraforming required.

SWM wrote:...

If you are talking about using plants (algaes are the ones usually suggested in the literature) to create an oxygen atmosphere from a CO2 atmosphere, then you are talking terraforming. And I already said that a planet like that would require significant terraforming. It would take many generations to generate a breathable atmosphere that way.

That is not exactly correct. That is what a "problematic" atmosphere like that of Venus would entail. The combination of extreme pressure, temperature and absence of enough of a non-interactive base-gas(like nitrogen on earth) means "fixing" Venus might require (many) centuries.

However, experimentation has showed that the changes needed in starting conditions to make it drastically easier are not huge.

And Venus is not an average case, knowledge so far says it´s far more likely to find a planet with a "more useful" starter atmosphere, one that should be "fixable" in a few decades or (much) less, depending on how much resources you pour into the project.

And algae and some plants has shown to have potentially quite amazing ability for terraforming. Even without fiddling with them.

Guesstimates are very uncertain as yet, but expecting 1/10 of suitable planets within the habitable zone to be "quick'n'easy" terraform projects isn´t unrealistic.


Also, this might be of interest:
http://en.wikipedia.org/wiki/List_of_po ... ts_Catalog

Take good notice that earth is NOT in the most optimal place in the habitable zone.

And remember, there is serious searching for traces of potential life on the moons Titan, Europa and Enceladus, and two of those 3 are moons of Saturn.

Grashtel wrote:

drothgery wrote:Who says we need habitable planets to colonize the stars?

Yep, the difference between a space habitat and a plausible sublight colony ship is that the habitat doesn't have engines and doesn't need to run for decades to centuries without external resources.

Exactly.

IMO, if we colonize the stars, it will be done by O'Neill colony inhabitants transitioning to generation ships...

(Also, I'm not ruling out lots and lots of Earthlike planets yet. According to my limited understanding, the radial velocity method works best for really big planets really close to stars, and the transit method Kepler uses only works for the tiny fraction of systems that are "edge on" to us.)

Tenshinai wrote:

SWM wrote:...

If you are talking about using plants (algaes are the ones usually suggested in the literature) to create an oxygen atmosphere from a CO2 atmosphere, then you are talking terraforming. And I already said that a planet like that would require significant terraforming. It would take many generations to generate a breathable atmosphere that way.

That is not exactly correct. That is what a "problematic" atmosphere like that of Venus would entail. The combination of extreme pressure, temperature and absence of enough of a non-interactive base-gas(like nitrogen on earth) means "fixing" Venus might require (many) centuries.

However, experimentation has showed that the changes needed in starting conditions to make it drastically easier are not huge.

And Venus is not an average case, knowledge so far says it´s far more likely to find a planet with a "more useful" starter atmosphere, one that should be "fixable" in a few decades or (much) less, depending on how much resources you pour into the project.

And algae and some plants has shown to have potentially quite amazing ability for terraforming. Even without fiddling with them.

Guesstimates are very uncertain as yet, but expecting 1/10 of suitable planets within the habitable zone to be "quick'n'easy" terraform projects isn´t unrealistic.


Also, this might be of interest:
http://en.wikipedia.org/wiki/List_of_po ... ts_Catalog

Take good notice that earth is NOT in the most optimal place in the habitable zone.

And remember, there is serious searching for traces of potential life on the moons Titan, Europa and Enceladus, and two of those 3 are moons of Saturn.

Before jumping on that bandwagon, it might be a good idea to review what we know of the Great Oxygenation Event on Earth. See http://en.wikipedia.org/wiki/Great_Oxygenation_Event .

The currently most popular view is that, starting with the conditions on Earth prior to the emergence of photosynthetic bacteria that create oxygen as a waste product to where oxygen levels are approximately what they are today was approximately two and a half billion years, and included the Huronian Snowball Earth event which lasted about 300 to 400 million years.

This time scale might cause even the most forward-looking transstellar corporation to downgrade the project's feasibility.

There's an alternative view that this occurred a lot faster, but IMO that's unlikely to be correct.

Now granted, a sample of one doesn't prove a whole heck of a lot, but at the same time it gives absolutely no support to alternatives that may be more pleasant to contemplate.

Tenshinai wrote:

SWM wrote:...

If you are talking about using plants (algaes are the ones usually suggested in the literature) to create an oxygen atmosphere from a CO2 atmosphere, then you are talking terraforming. And I already said that a planet like that would require significant terraforming. It would take many generations to generate a breathable atmosphere that way.

That is not exactly correct. That is what a "problematic" atmosphere like that of Venus would entail. The combination of extreme pressure, temperature and absence of enough of a non-interactive base-gas(like nitrogen on earth) means "fixing" Venus might require (many) centuries.

However, experimentation has showed that the changes needed in starting conditions to make it drastically easier are not huge.

And Venus is not an average case, knowledge so far says it´s far more likely to find a planet with a "more useful" starter atmosphere, one that should be "fixable" in a few decades or (much) less, depending on how much resources you pour into the project.

And algae and some plants has shown to have potentially quite amazing ability for terraforming. Even without fiddling with them.

Guesstimates are very uncertain as yet, but expecting 1/10 of suitable planets within the habitable zone to be "quick'n'easy" terraform projects isn´t unrealistic.


Also, this might be of interest:
http://en.wikipedia.org/wiki/List_of_po ... ts_Catalog

Take good notice that earth is NOT in the most optimal place in the habitable zone.

And remember, there is serious searching for traces of potential life on the moons Titan, Europa and Enceladus, and two of those 3 are moons of Saturn.

I was not using Venus as a typical example. I am curious where you have seen research suggesting that a breathable atmosphere could be produced in decades; I'd like to read that. I find it a bit hard to believe.

JohnRoth wrote:
Before jumping on that bandwagon, it might be a good idea to review what we know of the Great Oxygenation Event on Earth. See http://en.wikipedia.org/wiki/Great_Oxygenation_Event .

The currently most popular view is that, starting with the conditions on Earth prior to the emergence of photosynthetic bacteria that create oxygen as a waste product to where oxygen levels are approximately what they are today was approximately two and a half billion years, and included the Huronian Snowball Earth event which lasted about 300 to 400 million years.

This time scale might cause even the most forward-looking transstellar corporation to downgrade the project's feasibility.

There's an alternative view that this occurred a lot faster, but IMO that's unlikely to be correct.

Now granted, a sample of one doesn't prove a whole heck of a lot, but at the same time it gives absolutely no support to alternatives that may be more pleasant to contemplate.

There is a HUGE difference between something occuring by random chance, and someone making it happen intentionally following a planned process.

Diamonds are naturally created over millions of years, but in a lab, you can make them in hours. Well if you don´t mind only getting diamond particles, you can make them in milliseconds even(using explosives).

SWM wrote:I was not using Venus as a typical example. I am curious where you have seen research suggesting that a breathable atmosphere could be produced in decades; I'd like to read that. I find it a bit hard to believe.

Just try searching for terraforming, i have absolutely no idea how much is online since i got it "through the grapevine" so to speak, but nowadays there´s no reason it shouldn´t be online(hmm, a quick look tells me there´s more likely too much online).

And i only used Venus as an example of a really really BAD planet to try to terraform.

Consider terraforming as an industrial rather than biological process.

The Earth's current atmosphere masses about 10,000 Kg/m^2.

The Earth's surface area is on the order of 1eex14m^2.

Therefore the mass of Earth's atmosphere is on the order of 1eex18 kilogram.

Assuming that the gases in our candidate Carbondioxide atmosphere has an average heat of formation of about 10 megaJoules per Kg (someone will look it up), then ww need an energy input of 1eex23Joules.

We are assuming that this colony is being established by Weberverse STL technology where they have sent a colony ship massing perhaps 100,000 tons or 1eex8 Kg at 1/2 Cee, so the KE of the ship maxed out at 1eex24 Joules.

The energy input needed to terraform a planet is therefore on the order of 1/10 of the energy needed to send the colony ship,

Of course given how the initial mass of the planetary atmosphere might be higher and that a lot of the free oxygen formed will be fixed by oxidizing iron and other metals, the energy cost might be higher.

However; the concept of an atmospheric processing station as seen in ALIENS seems extremely plausible to me with a terraforming time measured in decades.