Astronomers report planet better than Earth!

[Cray]

It's the Onion (with strong language), but I suspect this satirical site is being prophetic.

We're finding extrasolar planets so quickly now that the question isn't when we're going to find an Earth-like planet, but what the headlines are like when we find a planet better than Earth.
http://www.theonion.com/article/astronom...kes--37986

[stevebowers]

This is going to be a difficult one. I expect that a lot of planets might look hospitable from a distance, but they'll be hell-holes close up. A lifeless planet would have nothing to breathe, and a life-bearing planet might have dangerous organisms (or at the least, inedible ones). So even if astronomers were to announce a hospitable world there would be plenty of room for doubt.

[Bear]

One thing that figures in the Reconstruction series is the idea of "tetralife." Mainly as a plot device to deprive the descendant cultures access to Earth. As the story goes in that setting, after life as we knew it got wiped out on Earth in The Kerpockeyclypse, tetralife arose in its place. Tetralife had been a theoretical study for a few decades at that point, and genomes for many tetralife species had been grown in simulation and worked out theoretically in research journals (which journals are known to the religious among the survivors as "The Books Of Abominations"). A limited set of these otherwise-theoretical species, mostly tetrafungi, had apparently been produced in actual molecules rather than just in simulation, and spores for "Shaitan's Toadstools" were evidently on the surface and viable after the Kerpockeyclypse.

Nobody's quite sure whether they were originally a contained biology experiment that was protected in some lab when the surface got irradiated, or whether they were deliberately deployed as weapons in the Kerpockeyclypse, but by the time of the stories, it really doesn't matter, because none of the polities responsible for the Kerpockeyclypse survived it.. Many different earth-descended groups have religious interpretations of tetralife's significance (as well as disagreements about the eschatological significance of the actual now-historical apocalypse and end of the world) though. Anyway, tetralife is "just" standard DNA-based life with a different set of ribosomes, so it codes for proteins in quartet groups rather than in triplet groups.

This gives tetralife a 4x larger 'vocabulary' of proteins that it can code for, and makes it possible for tetralife to be constructed with many proteins that are not used in trilife forms such as ourselves. Unfortunately, that means that while tetralife contains proteins that trilife cannot digest nor target with our immune defenses, the converse is not true. And therefore, now that the surface of Earth is more or less home to an ecology of tetraslimes, tetramolds, and tetrafungi, it means that unless we absolutely and completely sterilize it first, (which is damned hard because tetrafungus spores are at least an order of magnitude tougher than trilife fungus spores) just one breath of the air is reliably fatal for any trilife organism.

This left the remnant populations hanging on in the asteroid belts and space station habs in a really bad situation because they had all been relying on earth for resupply, repair parts, and infrastructure. So there was the mad scramble for survival, where about 80% of the offworld populations died off, and then the long hard slog of the reconstruction period where the stories are set, and aside from a couple of research stations that invest more in physical protection and fully-contained life support than the Mercury stations, nobody can live on Earth.

Anyway - a "moderately plausible" scenario about how Earth could go on to have a thriving, vibrant, diverse (well, diverse types of slimes, molds and fungi anyway) ecology with absolutely no space for us anywhere in it.

[iancampbell]

Bear - I think it's worth mentioning that the existing triplet code has a fair amount of room for expansion. AFAIK, only about 30 of the possible 64 triplets are actually used in Earthly life. And life would probably not necessarily have to use the same amino acids, of the same coding, as ours.

For something a bit more extreme, I offer a very old story (1950s I think) about Earth explorers coming back extremely late, after an accident with an experimental hyperdrive. (Yes, I know OA doesn't have such but it was more of a plot device than anything else.) They found a thriving ecosystem - in a completely unbreathable atmosphere, with life forms that had evolved from some autonomous mining barges left to fend for themselves after some eco-disaster. Basically, a planet full of living robots.

I just wish I could remember the author and where I found it...

[Matterplay1]

Bear - I think it's worth mentioning that the existing triplet code has a fair amount of room for expansion. AFAIK, only about 30 of the possible 64 triplets are actually used in Earthly life. And life would probably not necessarily have to use the same amino acids, of the same coding, as ours.

For something a bit more extreme, I offer a very old story (1950s I think) about Earth explorers coming back extremely late, after an accident with an experimental hyperdrive. (Yes, I know OA doesn't have such but it was more of a plot device than anything else.) They found a thriving ecosystem - in a completely unbreathable atmosphere, with life forms that had evolved from some autonomous mining barges left to fend for themselves after some eco-disaster. Basically, a planet full of living robots.

I just wish I could remember the author and where I found it...

There are some interesting analyses of the particular DNA-to-proteins coding we have that seem to indicate that it might actually be an optimal arrangement for error-reduction. For those interested, there's a good summary of this in deDuve's fascinating book on singularities in evolution (not the OA variety, but singular results/events):

Singularities: Landmarks on the Pathways of Life

As for the short story about evolved descendants of self-replicating robots, that was by Poul Anderson and is called "Epilogue". I wish I had a copy, but I just went to look in my library and couldn't find a collection that had it. Memorable, though, and one of the inspirations for the OA Encyclopaedia Galactica article "Stanislaw" (the second inspiration is of course in Stanislaw Lem's book "The Invincible").

[Drashner1]

Anyway - a "moderately plausible" scenario about how Earth could go on to have a thriving, vibrant, diverse (well, diverse types of slimes, molds and fungi anyway) ecology with absolutely no space for us anywhere in it.

Hm. Not sure if we could do this without seeming derivative of this other setting, but Terragens being what they are, if this sort of thing is possible, someone somewhere has probably created this kind of ecology (on a hab, moon, or planetary scale) just for the fun of it or something. Probably a write up or two in that.

Todd

[Matterplay1]

As for the short story about evolved descendants of self-replicating robots, that was by Poul Anderson and is called "Epilogue". I wish I had a copy, but I just went to look in my library and couldn't find a collection that had it. Memorable, though, and one of the inspirations for the OA Encyclopaedia Galactica article "Stanislaw" (the second inspiration is of course in Stanislaw Lem's book "The Invincible").

Here's a review of Anderson's story:
http://polaris93.livejournal.com/2745134.html

[Rynn]

Anyway, tetralife is "just" standard DNA-based life with a different set of ribosomes, so it codes for proteins in quartet groups rather than in triplet groups.

This gives tetralife a 4x larger 'vocabulary' of proteins that it can code for, and makes it possible for tetralife to be constructed with many proteins that are not used in trilife forms such as ourselves.

Triplet coding is for amino acids, not for proteins. Triplet coding with four base pairs gives us 64 possible combinations, in nature only 20 of these are used. The excess combinations are used for redundancy (multiple codes per amino acids means that likely mutations in base pair sequence are less likely to change the amino acid sequence). There have been synthetic amino acids created that presumably a larger coding system would code for but there's an interesting question of whether or not these would be favourable in any environment. Or to put it another way, are the few seen in nature in existence because they are more (bio)chemically favourable?

In any case a protein created by a quad-coding system wouldn't automatically be incompatible, it may even be identical to others if the amino acid sequence is kept. It's if there are any extra AAs that might be toxic or otherwise harmful to humans that would make the difference.

[sandcastles]

What is the Reconstruction series Bear mentioned?  Google doesn't find Kerpockeyclypse anywhere but here.  I was looking for mentions of Poul Anderson and found this.

Also, Bear was working on Iota Librae and that doesn't have its own article yet.  I wondered about contributing something to that.

Thanks.