The researchers were astounded upon finding 48 distinct species still surviving in the cave, which had been isolated for millions of years.

Defining alien life, we can say that it is a form of life that evolved on a planet with a different gravity and atmosphere than Earth. In other words, the variations in the conditions on different planets result in distinct forms of life.

It may seem implausible, but it is a fact that for millions of years, a parallel Earth has been developing somewhere on our planet, and a variety of different species, including some of the rarest alien species not found anywhere else on Earth, have been inhabiting it.

Discovery of the Movile Cave

While installing a power plant in 1986, workers in communist Romania stumbled upon the location in Constanța county near the Black Sea and Bulgarian border.

While exploring an infertile, featureless plain near the Black Sea and Bulgarian border, workers in communist Romania discovered a mysterious cave. This cave had been sealed off from the rest of the world for nearly 5.5 million years, a time when our ape-like ancestors were transitioning from tree-dwellers to modern humans. Scientists later named it the "Movile Cave."

Adverse condition for life in the Movile Cave

Researchers found that the Movile Cave's atmosphere is highly toxic, primarily due to the presence of carbon dioxide (CO2), hydrogen sulphide (H2S), and ammonia (NH3) gases emitted from the water inside the cave. Oxygen levels are only 10% and there's no visible source of food or light in the cave. The cave also contains 1-2% methane (CH4) which is non-toxic but highly flammable and can form explosive mixtures with air.

Strange species in the Movile Cave

Despite the cave's inhospitable conditions, researchers were surprised to find 48 different species living inside, including 33 rare species found nowhere else on Earth.

The researchers found distinct, unique species including spiders, leeches, water scorpions, pseudo-scorpions, centipedes, snails, and woodlice, each with a unique biology not previously observed. Among these, Nepa anophthalma is the only known cave-adapted water scorpion in the world.

The animals living in the Movile Cave did not all arrive at the same time. The most recent animal recorded is the cave's only species of snail, which has lived there for just over 2 million years.

How do they survive inside this bio-adverse cave?

All of these peculiar creatures have a complete dependence on an enigmatic and unusual layer of bacteria to sustain their lives.

To clarify, the food chain in the cave relies on chemosynthesis, where methane and sulfur-oxidizing bacteria release nutrients for fungi and other bacteria. These microorganisms form microbial mats on the cave walls and surfaces of lakes and ponds, which are consumed by some of the animals. These animals are then hunted by predatory species.

Conclusion

It's remarkable that all inhabitants of this cave have been completely isolated from the rest of the world for over 5 million years, it is like a separate world hidden on our planet since prehistoric times.