Until it's found and observed closely its origin is unlikely to be known. But there is a strong possibility that it is a captured rogue planet. If it does turn out to be of interstellar origin then that would be very exciting indeed, for it could have brought with it a tantalising glimpse into the possibilities of life and even civilisations that formed hundreds or even thousands of light-years away.
The planet is expected to be a smaller version of Uranus or Neptune with a thick and deep atmosphere of mainly hydrogen. With a mass ten times that of Earth it would be just less that four times the diameter of our world. If so, there is little chance of life on its surface.
It could well be a different story on its moons.
|One of Planet Nine's ice moons|
Such moons, preserved over the aeons by the deep cold of interstellar space, could well be a treasure trove of artifacts from hundreds of millions of years ago that point to the existence of intelligent life that evolved in a star system far from ours, and when the moon's parent world was in a stable position around its home star. If the civilisation was relatively primitive (no more advanced than ours) it would have ended when some catastrophic event, such as a close encounter with a passing star, dragged the parent world out of its home star system and banished it to the interstellar void.
But if, during such an event, a technologically advanced civilisation existed on one of those moons, it would surely have gone to great lengths to preserve its existence as long as possible. We may well find evidence of deep habitats, seed banks, and even knowledge banks or cultural archives.
|The frozen surface of one of Panet Nine's moons. Could the artifacts of an extra-terrestrial civilisation from hundreds of light-years away be hidden beneath the surface?|
But what if some remnant of that civilisation still survives, somehow utilising the decaying heat of the moon or parent planet's interior for energy? Rogue planets are not necessarily the lifeless worlds we usually imagine (see my earlier article on rogue planets).
Another intriguing idea is that a civilisation, aware of its decline towards extinction on its home world, colonised Planet Nine as it passed close by. Using the rogue planet as natural interstellar generation ship, the colonists would have planned for a voyage of hundreds of millions of years with an indeterminable destination. They would have also had to prepare for the possibility that no suitable star system would ever be reached.
To ensure survival such preparations would have to include a meticulously designed ecosystem, safely contained from the harsh interstellar void. This would most likely be beneath the ice of a moon with access to the ocean beneath. Such an ocean, seeded with life from the civilisation's home world, would be the most likely source of food, water and oxygen for the colony. And it could be a source that could indeed, with disciplined management, provide for a journey and time span of such magnitude.
There is great risk in embarking on such a journey. After tens of thousands of generations the colonists may well lose sight of their ultimate aim. Such a subterranean existence would change a civilisation from an outward looking and curious culture to a simpler and inward looking one focused more and more on nothing but its day to day existence. Devolution could occur, with physical and mental abilities simplifying over the generations to match the environment. Intelligence could dwindle, and physical dexterity could lessen. Technological systems, if self maintaining, could continue to function indefinitely, looking after the colonists who no longer comprehend the machines that keep them alive.
|Ancient self-maintaining machinery that could support a subterranean ice moon colony for millions of years|
Such a colony could be thriving right now on one of the moons of Planet Nine, well adapted to their subterranean existence, and unaware of our existence and even that they are now part of our Solar-System. There may even be no knowledge or concept of the universe beyond their ice-shrouded domain. The colony would function in an eusocial manner, like a society of ants. It would be a collective of simpler minds working together, more by instinct than planning, to ensure survival.
Colonies like this could be intentional rather than evolutionary. A technologically advanced civilisation could engineer a version of its species to function in a eusocial manner and create colonies beneath the surface of numerous ice moons. The colonies would survive in the simplest manner possible, ready for higher intelligence levels to be reinstated, most likely by automated systems, when the time is right. At that time, upon entry into a star system with a suitable planet for the colony to live on, the automated systems would genetically modify the next generation to possess a high enough level of sentience and sapience so that it could be educated.
|Automated systems re-engineering a new generation of intelligent colonists ready to be educated before travelling to their new home planet|
Over the next few generations the advanced technological civilisation that created the colony millions of years before would be restored. Awareness of the universe beyond the ice would return, along with the curiosity and motivation necessary to leave the safety of its confines.
|A colonisation spacecraft, maintained by automated systems for millions of years, is readied for launch as a viable star-system is reached|
There could be a huge number of such subterranean, almost troglodytic, colonies, set up to allow species to survive for hundreds of millenia as rogue planets make their natural interstellar journeys.
We would need to be very careful if evidence of such a colony is discovered. Our appearance within their colony could devastate it. We should monitor it carefully, without disturbing the delicate balance that has kept it alive for so long. The way the colony functions, and the machinery to maintain it, could teach us a lot about survival.
Planet Nine may turn out to be one of many captured interstellar objects in the outer Solar-System. Such objects would be a rich source of evidence about the environments around other stars, and could well contain the preserved remains of extra-terrestrial civilisations, and even the surviving descendants of such civilisations.
The discovery and exploration of such objects should be a priority. The knowledge we gain could transform our unstanding of the possibilities of life beyond the comforts of Earth.
It could even save our species.