Scientists unanimously agree that it is tardigrades.
The first to study this microscopic (0.1–1.2 mm) invertebrate was the Italian zoologist Lazaro Spallanzani in the 1770s. He named it "tardigrade," which in Italian is il tardigrado, and this name later became established in zoology in its Latin form — Tardigrada. Tardigrades cannot exist without moisture: they inhabit freshwater bodies, damp soil, permeable mosses and lichens, as well as the trunks of trees and rocky mountains.
If there is insufficient moisture, tardigrades enter a state of anabiosis (apparent death). This may seem incredible, but even after 100 years, a desiccated tardigrade can be "awakened" with a drop of water. Overall, among living beings, tardigrades are unmatched in endurance under extreme conditions.
According to research, tardigrades in a state of anabiosis can withstand cooling down to -271 °C for several hours, survive brief heating up to 150 °C, and endure significant radiation exposure and high pressure.
Japanese scientists conducted an experiment in which "sleeping" tardigrades were placed in a sealed container and submerged in a high-pressure chamber, gradually increasing the pressure to 600 MPa (which is nearly 6 times the pressure at the lowest point of the Mariana Trench). As a result, the majority of the test tardigrades successfully passed this test, which would be impossible for other living beings to withstand.
