Where is the limit of the human body? Physiologically, people can persist for 3 weeks without food; they can persist for up to 3 to 4 days without drinking water; and more than 3 minutes of brain hypoxia can cause irreversible damage. In contrast, the vitality of microbes seems to be more tenacious, not only in every corner of the biosphere, but also in places where there are no sunshine, no oxygen, high temperature and high pressure in the thousands of meters below the surface.
Huge underground biosphere
Scientists have been wondering where most of the microbes that are invisible to the naked eye are living. So they have been digging and digging all the time, trying to find a critical point where life does not exist. As a result, the deeper they dig, the more life they discover and the limits are constantly broken.
As early as the beginning of the 20th century, scientists have conducted extensive research on the tens of thousands of holes drilled by humans on Earth and the life activities in various mines and caves to explore the possible life in the deep earth. In 2007, scientists acquired thermophilic bacteria about 3.2 kilometers underground in the South African gold mine. In 2008, scientists also discovered microorganisms from mineral samples from 1.6 kilometers below the sea floor, and speculated that they could tolerate 60 ° C to 100 ° C. high temperature. With in-depth research, scientists have found that there is a hidden new world hidden in the depths of our surface, and its life is far more abundant than imagination.
How big is this underground biosphere? Based on data from hundreds of experimental sites around the world, scientists estimate that the biosphere at our feet can go deeper than 4 to 4.5 kilometers below the surface. Its size may range from 2 billion to 2.3 billion cubic kilometers, which is almost twice the size of the Earth’s oceans, and this size may expand further in the future. Bacteria and archaea, the two forms of microbes, are the protagonists of this underground biosphere, where 70% of the planet’s microbes live. If calculated based on the mass of carbon, the total weight can reach 15 billion to 230. Billions of tons are hundreds of times the total weight of carbon contained in humans on Earth. And we know very little about it because their habitat is too difficult for humans to enter.
So far, the deepest record of known life is 5 km below the surface of the land and 10.5 km below the surface of the ocean. The most heat-resistant bacteria can survive in an environment of 121 ° C. These are the results of 10 years of research by 1,000 scientists from 52 countries. However, scientists say that despite these findings, the lower limit of the underground biosphere is still a mystery.
What do underground residents eat?
Solar energy is the energy base of the biosphere. In the biosphere, there are plants that grow and develop using solar energy, various animals that feed on plants, and microorganisms that live by saprophytic life by decomposing animal wastes and organic matter in the remains. Investigate the roots, these creatures rely on solar energy to survive.
The biosphere we are in is about 10 kilometers above sea level, down to 10 kilometers, and 20 kilometers thick, but in fact most organisms usually live on land and below the surface of the ocean about 100 meters thick. Within the scope. why? Because outside this range, the thinner the air and the lower the temperature, the more the species will become less and more on the ground, and the underground will lack light, the oxygen content is low, and the depth of the crust is deep. For every additional kilometer, the temperature rises by 20 ° C to 30 ° C, which is a high temperature environment. How can such an extreme environment exist?
It turns out that the harsh environment does not stop the pace of microbes. So how do they survive under the conditions of darkness like hell?
Unlike the “relatives” on the ground, microbes living in the interstitial spaces of the rock mainly acquire energy from the surrounding rock minerals by means of chemical synthesis. They can oxidize hydrogen, methane (which can be produced by certain types of rocks in high temperature and high pressure environments) to obtain chemical energy to supply their own survival needs. The limited source of energy makes their metabolism almost stagnant, and the life cycle is extremely long, even for thousands of years. Its slow-paced life is beyond the reach of humans on the ground.
Exploring the existence of life in outer space
The discovery of the underground biosphere has made scientists excited. On the one hand, these microbes that grow in special environments may have special functions that are not yet clear, and if they can be explored and utilized, they will benefit humanity. On the other hand, the deep environment of the earth is similar to the high temperature, high pressure and anaerobic environment when the earth was born. These microorganisms that can synthesize organic matter without relying on the solar light source may be left in the Taikoo era. Exploring the underground biosphere can explore life for us. Origin offers another possibility.
More importantly, since there is life in such an extreme environment in the deep earth, can planets such as Mars and Jupiter be able to give birth to life? The survival of these underground microorganisms does not require oxygen. Exploring life phenomena outside the earth does not necessarily presuppose oxygen. Understanding their survival means that we can find signs of extraterrestrial life. There are still many questions waiting for scientists to explore and discover the biosphere in the deep Earth.