[Space] Panspermia and the Campgaign

[Flyndaran]

Originally Posted by Nereidalbel

If your star system has some ice ball planets and/or moons at the outer reaches, life could evolve in the oceans underneath icy crusts, and occasionally be thrown out into space via geysers. I mean, there has to be a reason tardigrades can survive floating around in space and such...

Also, if any microbial life could go dormant and float around in space for a period of time without needing to hitch a ride on an asteroid or comet, they could feasibly float into an atmosphere without being roasted.

The reason is that "dead" dry things are hard to kill. They survive by desiccating themselves to metabolic stoppage. Damaging living cells is easiest when they're dividing and active. No water to boil, and no mitosis to screw up. Also they can't survive the centuries or millennia it takes to drift to even a close planet.

[Nereidalbel]

Originally Posted by Flyndaran

The reason is that "dead" dry things are hard to kill. They survive by desiccating themselves to metabolic stoppage. Damaging living cells is easiest when they're dividing and active. No water to boil, and no mitosis to screw up. Also they can't survive the centuries or millennia it takes to drift to even a close planet.

You never know. I mean, we've gone and resurrected seeds frozen for over 10,000 years, so...lasting several millennia isn't an issue for life.

[Flyndaran]

Originally Posted by Nereidalbel

You never know. I mean, we've gone and resurrected seeds frozen for over 10,000 years, so...lasting several millennia isn't an issue for life.

Frozen on earth isn't even close to the harshness of space.
Not to mention expert botanists getting a few seeds to germinate isn't even close them surviving on their own after crashing on an alien planet.

The only things I can imagine having any chance of surviving such a scenario are very hardy encased in stone archaea.
But they are so distantly related to us as to almost require their multi-billion year descendants be as alien as unrelated aliens with similar biochemistry.

[Nereidalbel]

Originally Posted by Flyndaran

Frozen on earth isn't even close to the harshness of space.
Not to mention expert botanists getting a few seeds to germinate isn't even close them surviving on their own after crashing on an alien planet.

The only things I can imagine having any chance of surviving such a scenario are very hardy encased in stone archaea.
But they are so distantly related to us as to almost require their multi-billion year descendants be as alien as unrelated aliens with similar biochemistry.

That it can happen at all is just a testament to how durable life really is. If it can be done once in a lab, there's no reason it can't happen somewhere in the Universe, given billions of years.

[scc]

Originally Posted by jeff_wilson

That's not the whole story; pre-life Earth did not have a breathable atmosphere or surface water and you can see how Venus has a similar distance from the sun but a very different condition from earth's current one.

Right, other then the planet life evolved on I've got half a dozen planets like this, if I can just transport some of the that made the first planet habitable to the others, everything's good.

And the meteorite I mentioned from Earth to Mars and back again was on the news several years back

[jeff_wilson]

Originally Posted by scc

Right, other then the planet life evolved on I've got half a dozen planets like this, if I can just transport some of the that made the first planet habitable to the others, everything's good.

And the meteorite I mentioned from Earth to Mars and back again was on the news several years back

Yes, but it was a different one than the one with supposed microbe fossils, and may have been discredited if a current grad student can't locate a reference.

[lwcamp]

Originally Posted by Nereidalbel

If not on Europa, the original Star Trek series may have had it right with silicon-based life in an anoxic environment.

Silicon doesn't look like a good replacement for carbon for making life. It just can't easily form the long polymers that carbon can, so you don't get analogues of DNA, RNA, proteins, or fatty acids.

Originally Posted by Nereidalbel

What doomed Venus was the lack of a carbon cycle more than anything. On Earth, plate tectonics ensure that carbon is cycled through the mantle regardless of life, while Venus only experiences any sort of recycling in massive events every few hundred million years. Accelerate Venus' rotation enough to weaken the crust, and it may actually be habitable.

This sounds like a chicken-and-egg problem. Consider the following scenario, starting with a Venus with a full plate tectonics cycle and an atmosphere consisting primarily of nitrogen at about 1 Earth atmosphere of pressure :
* The increased insolation of Venus results in two effects - (1) more water evaporates so there is more water in the atmosphere, and (2) the water can rise higher in the atmosphere before it condenses and rains out.
* Water is a strong greenhouse gas, so the thicker blanket of water results in even higher temperatures, which leads to more water and thicker blankes of water due to its higher altitude, leading to even more water in the air and even higher altitudes before condensation.
* The water rises high enough in the atmosphere that significant ultraviolet light can get through and hit the water. The water is photodissociated into hydrogen atoms and hydroxyl radicals. The hydrogen escapes into space (Jeans escape), and over time the water starts to dissapear leaving an atmosphere enriched in oxygen behind.
* While this is happening, surface temperatures get high enough to bake carbon dioxide out of lime deposits. Now the carbon dioxide acts as a greenhouse gas as well, accelerating the process.
* Oxygen reacts with minerals in the venerian crust, and is removed from the air.
* Water is a major lubricant for plate tectonics here on Earth. As water is removed from the air, it gets harder for the plates to move around and eventually the tectonic cycle grinds to a halt.
* The water is eventually fully photolyzed and drifts away. This leaves a world with a thick atmosphere of carbon dioxide and no plate tectonics.

Luke

[thrash]

Originally Posted by jeff_wilson

Yes, but it was a different one than the one with supposed microbe fossils, and may have been discredited if a current grad student can't locate a reference.

I'm not sure how you could even tell it had ever been on Mars.

So far as I know, tektites are the only Earth rocks known to have been in space. They were only suborbital, however.

[whswhs]

Originally Posted by Flyndaran

We only have one regardless of defined area. The defined area is highly arguable, but the one is not.
Sapience on par with parrots, great apes, and dolphins isn't what I mean when I write about human type intelligence.

I don't understand why this is relevant. We have one known life-bearing planet and it has human-level intelligence. Why does it need to have more than one species with human-level intelligence? That seems like moving the goalposts.

Bill Stoddard

[whswhs]

Originally Posted by Nereidalbel

Well, silicon works pretty damn well on any planet where photosynthesis never kicks in. Kinda crap once oxygen becomes a thing, though.

Silicon by itself doesn't seem likely to form useful information-bearing polymers. At least I don't know of anything comparable even to hydrocarbon chemistry based on it.

Bill Stoddard