I have a bacterial organism called the "World Blight" this creature's life cycle revolves around being introduced to a new planet, spreading across the planet and terraforming it to its liking, and then somehow reproducing. This organism is an extremophile being able to withstand extreme heat, cold, pressure, acidity, salinity, and nearly every other harsh condition thrown at it. It spreads across the planet by ingesting available minerals and compounds spreading across the planet like a mold, slowly covering the entire surface after being introduced. How can my organism spread itself from one planet to the next and possibly from one solar system to the next without help from sapient beings or technology?
Massive explosions seem like a good way. They can happen in the following ways:
- Asteroid impact: some of the ejecta can reach escape velocity and fly into space (we have some Martian meteors on Earth because of that). It's a totally passive method.
- Volcanic eruption: if the explosion is powerful enough it can project something into outer space with enough velocity to escape gravity hole. This is also passive, unless the mold can somehow stimulate the volcanic activity of the planet
- Nuclear explosion: during nuclear explosion escape velocity can be achieved and surpassed (see test Plumbbob)
During the Pascal-B nuclear test, a 900-kilogram (2,000 lb) steel plate cap (a piece of armor plate) was blasted off the top of a test shaft at a speed of more than 66 km/s
Though you are not interested in the latter, it can be the most interesting, if you suppose that the mold triggers the formation of intelligent life forms which develop and test nuclear weapons. So that the intelligent species is just an escape tool for the mold, not actually a helper.
Another possibility, this organism could spread as some fungi do, only on a bigger scale. These fungi creates a kind of blister that at some point explodes, spreading their spores around.
So your World Blight could create on the planet some giant blister-like structures, that at some point explode (they could be sealed structures and accumulate pressure thanks to some fermentation-like reaction) with enough strenght to give its spore the needed escape speed. If the speed is not enugh to leave the star system, anyway the spores could easily colonize almost all the objects orbiting around the star.
This way, comets and far planetoids, which are more likely to be ejected from the system because of gravitational interations, could spread the blight to other stars. In the interstellar vacuum they would hybernate (or slow down their metabolism), and will start to create and make explode new blister structures once they are near enough to be warmed by the radiation of another nearby star.
The organism first erodes bedrock into verticle shafts, tens of meters deep.
Through a series of complex metabolic processes it begins to generate a build-up of waxy deposit at the bottom of the shaft - this grows, till it fills half the shaft then stops.
Next, like an iris closing, the top of the shaft becomes sealed with a tough plug of resinous mass.
Attribution abduh137 2019.
The waxy substance - a high explosive with a super-high detonation speed in the order of 15km per second - in a massive explosion, triggering a cascade of similar explosions from nearby shafts, blows the resinous masses out of Earth's gravity well, they then make their way into interstellar space - all the time gradually shedding bacterial spores to be taken on the whims of the solar wind to new worlds to conquor.
If you're wondering about the feasability of a high explosive being enough - we have one which is almost up to the job - Octanitrocubane. It's detonation speed is 10.1 km per second, just 1 km per second shy of escape velocity. Atmo resistance should be easily overcome by one at 15 km per second.
The obvious answer is the stage tree, the literary invention of science fiction author Larry Niven. Stage trees are biologic rockets, with the wood replaced by (essentially) solid fuel. After they reach full size, they self-ignite and propel a seed payload capable of reaching another solar system. Admittedly, the trip takes a long time, but seeds don't get bored.
The concept also surfaces in Charles Stross's Rogue Farm
Stage trees started out as science fiction, like? Some guy called Niven — anyway. What you do is, you take a pine tree and you hack it. The xylem vessels running up the heartwood, usually they just lignify and die in a normal tree. Stage trees go one better, and before the cells die they nitrate the cellulose in their walls. Takes one fuckin’ crazy bunch of hacked ‘zymes to do it, right? And lots of energy, more energy than trees’d normally have to waste. Anyways, by the time the tree’s dead it’s like ninety percent nitrocellulose, plus built-in stiffeners and baffles and microstructures. It’s not, like, straight explosive — it detonates cell by cell, and some of the xylemtubes are, eh, well, the farm grows custom-hacked fungal hyphae witha depolarizing membrane nicked from human axons down them to trigger the reaction.
You could give your mold a very very long lifespan were it waits for the host star to go supernova tossing seeded asteroids across the galaxy.
The organism could reproduce in something akin to a lighter than air spore or a gravity resistant coated spore that will reach the edge of space/atmosphere on any given planet then it could hitchhike on solar wind or charged particles that travel through space.