The narrative discusses the concept of rogue planets, which are planets that travel alone through the universe, inhabiting the dark and vast space between the stars. These planets are exposed to the freezing cold of outer space and have no seasons, days, or nights to indicate the passage of time. Despite this, they might carry alien life to all corners of the galaxy.
The narrative then delves into the formation of rogue planets. Young star systems are dangerous places where protostars are battling for available mass, guzzling up as much material as possible. If a very massive planet moves its orbit closer to the star, it can kick smaller planets out of the system. However, just because a planet has survived the growing pains of formation doesn't mean it's safe. Planetary systems can be disrupted by flybys from stars or black holes at any point.
The narrative then discusses the possibility of life on rogue planets. As far as we understand the nature of life, it needs liquid water. Water is important because it mixes both matter and energy, which lets interesting chemistry happen like life. So, a rogue earth needs to work with the 0.03 percent of energy it has left, which almost exclusively comes from its hot center.
The narrative then discusses the possibility of an earth-like planet having oceans that are not frozen over if the planet had an extremely dense and high-pressure hydrogen atmosphere. The gas would not freeze and could trap enough of the heat trying to escape the planet to enable oceans that extend all the way to the surface.
The narrative then discusses the possibility of life sustaining itself at the bottom of a completely dark, cold ocean on a rogue planet. It mentions hydrothermal vents, called black smokers, that spew out a cloud of black material and hot water, providing a constant flow of minerals from earth's mantle. Bacteria feed on the minerals and produce organic materials which attracts crustaceans, bivalves, snails, fish, octopus, and tube worms up to two meters long.
The narrative then discusses the possibility of life emerging in such an environment. If it did, it would find itself in a pretty weird world, constricted by an impassable wall of rock-hard ice at the top and bedrock at the bottom without any plants to store star energy. Our intelligent alien friends might never break through the ice and might never realize that there is such a thing as outside and assume that their small world is all there is.
The narrative then discusses the possibility of these frozen, dark deserts trapping the remnants of cultures and ecosystems forever as the oceans completely freeze and all life vanishes.
Finally, the narrative discusses the possibility of these worlds frequently passing the solar system without us even knowing. Maybe one day in the far future, humans will set foot on one of these frozen worlds and try to say hello.
1. Rogue planets are planets that travel through the universe alone, inhabiting the dark and vast space between the stars. They drift alone through eternal darkness, with no light warming their surfaces and no seasons, days, or nights to indicate the passing of time [Document 1].
2. There are several different things that get called rogue planets. For example, sub-brown dwarfs, gas giants that form from collapsing gas clouds, and terrestrial planets similar to Earth that got kicked out of their planetary system [Document 1].
3. Young star systems are dangerous places where protostars are battling for the available mass, guzzling up as much material as possible. If a very massive planet moves its orbit closer to the star, it can kick smaller planets out of the system [Document 1].
4. Planetary systems can be disrupted by flybys from stars or black holes at any point. Up to half of all planets born could end up as rogues. Scientists don't agree on the numbers, but it's likely that there are billions of rogue planets in the Milky Way alone [Document 1].
5. Most rogues will share the same depressing fate as their star becomes smaller day by day. The planet's surface quickly cools down to minus 270 degrees Celsius. If they have oceans, they'll freeze and become as hard as bedrock. Their atmospheres will sink down to the surface and eventually freeze too [Document 1].
6. Some of these frozen dark deserts could harbor life. To understand how, let's imagine a planet similar to Earth in the same order of magnitude in terms of mass and composition [Document 1].
7. As far as we understand the nature of life, there is one indispensable ingredient it needs: liquid water. Water is important because it mixes things both matter and energy which lets interesting chemistry happen like life [Document 1].
8. Our planet needs enough energy to keep at least a part of our oceans warm enough to sustain liquid water. About 99.97 percent of Earth's energy budget comes from the sun [Document 1].
9. Earth's inner core is a giant metal ball about as hot as the surface of the sun. That's surrounded by the outer core made up of liquid metals that are very slowly solidifying, releasing a lot of heat in the process [Document 1].
10. As long as this process is ongoing, our planet will be geologically active with solid and liquid material moving around and transporting energy to the surface where it can be harnessed as geothermal energy [Document 1].
11. There's even one scenario that could allow an Earth-like planet to have oceans that are not frozen over if the planet had an extremely dense and high pressure hydrogen atmosphere. The gas would not freeze and could trap enough of the heat trying to escape the planet to enable oceans that extend all the way to the surface [Document 1].
12. If a rogue planet brings a moon or more along with them, a large enough moon could inject additional energy into the system via tidal forces [Document 1].
13. The most likely scenario for a rogue bearing life is one with subglacial oceans under a kilometer thick layer of mostly water ice [Document 1].
14. In the dark ocean of a rogue planet, similar events or volcanic activity could be the starting point and basis for complex ecosystems [Document 1].
15. The most likely forms of life are bacteria and other microorganisms. Given enough time, more complex alien animals could feed on the smaller beings and thrive [Document 1].
16. It's not impossible that intelligent life could emerge in such an environment. If it did, it would find itself in a pretty weird world, constricted by an impassable wall of rock-hard ice at the top and bedrock at the bottom without any plants to store star energy [Document 1].
17. Worlds like this could frequently pass the solar system without us even knowing. Maybe one day in the far future humans will set foot on one of these frozen worlds and try to say hello [Document 1].