Somewhere hundreds of millions of kilometers from the surface of the Red Planet, long columns of numbers and symbols ran across the monitors of the Control Center. The planetary specialist who decoded them right from the screen cried out in surprise. The sample clearly contained a special type of clay - smectite, which on our planet can be found only on swampy plains, abundantly washed by monsoon rainfall.
Where are you, aliens?
Most likely, in that vast desert world, permeated with the icy breath of dust storms with daily temperature fluctuations of 80 ° C, billions of years ago, under the warm blanket of the atmosphere, streams murmured and the sea surf was rustling. Moisture poured over the edges of Gale Crater, flowing into Yellow Knife Bay Lake. The sky was violet-blue with a scattering of white cirrus clouds, and the relief had not yet acquired a reddish-brown hue. And above all this splendor towered five-kilometer Mount Sharpe, covered with a dazzling white snow cap.
Traces of compounds of carbon, hydrogen, oxygen, nitrogen and sulfur were also found in ancient clay. All these elements are part of the organic elements of which the terrestrial protein-hydrogen life is built.
So the NASA Curiosity rover, which had been carefully lowered to the surface with a special “sky crane” six months earlier, discovered traces of the planet's rich geological past.
After walking only a few hundred meters from the landing site, the curious rover stumbled upon a shallow depression of Yellow Knife Bay, where living organisms could once have lived. It is difficult to say what the ancient Martians were like - bacteria, mosses or lichens, but one thing is clear: for the first time outside the Earth, a place was found where life could really exist …
Why so far we have not met not only living aliens, but also their traces?
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Life zone
The fact is that the most amazing and, apparently, the rarest phenomenon of life, not to mention the mind, can arise and develop only on planets of a certain type. And let's not forget that such planets must revolve around the star in a kind of "life zone".
In our solar system, the "life zone" is occupied by only three planets - Venus, Earth and Mars. In this case, the orbit of Venus passes near the inner border, and the orbit of Mars - near the outer border of the "zone of life". Planet Earth is lucky, there are no high temperatures of Venus and the terrible cold of Mars. The last flights of robotic rovers have shown that the Red Planet was once warmer, and also there was water in a liquid state. And it is possible that traces of the Martian civilization, so many times and colorfully depicted by science fiction writers, will someday be discovered by space archaeologists.
Until relatively recently, scientists considered the surface of Mars to be completely dry, until their attention was attracted by strange dark stripes that appeared in the Martian spring, expanded in summer, sharply narrowed in autumn and practically disappeared in winter. Some scientists believe that this is definitely indicative of a freeze-thaw season. Microorganisms may well live under the surface of Mars. Is it possible to reliably estimate the probability of the origin of life and intelligence in the Universe?
Water-water, water everywhere …
In the past year, many supporters of the existence of alien life celebrated the great success of observations with the Kepler space telescope. First of all, it was the discovery of aquatic planets. And on them life of an earthly type could exist. They revolve around their stars in the habitable zone, where water - the main component of our life - would not freeze or boil, but remained a cool liquid, forming seas and oceans.
Life on our planet originated in the aquatic environment. And living things consist of exactly those chemical elements that are found in abundance in sea water. There are no mysterious ingredients in the chemical composition of living beings, no rare, "magic" primary elements, for the acquisition of which it would take an unlikely coincidence.
On any planet with a mass and temperature like that of the Earth, one should also expect the presence of oceans of water with a solution of salts of the same type. Accordingly, the life that originated there will have a chemical composition similar to the terrestrial living matter. Does it follow from this that in its further development such life will repeat the earthly one?
Here you cannot be absolutely sure. Many different combinations can be assembled from the same chemical elements. It is possible that in the youth of our planet, at the very dawn of the birth of life, thousands of fundamentally different living forms swam in the primitive ocean. Let us assume that one of them defeated all the others in the competitive struggle, and here it is no longer possible to deny that this happened by pure chance. And now the uniqueness of the presently existing life can push us to the false conclusion that it is precisely such a structure of living matter that is inevitable.
In November 2012, a team of researchers from NASA revealed that Mercury, where temperatures rise to nearly 450 ° C, contains more than 100 billion tons of ice in its constantly shaded craters. Even on the Moon, once considered the driest place in our solar system, a water cycle was discovered in 2010.
Some observations suggest that large satellites of the gas giants, such as Ganymede and Europa near Jupiter, and Titan and Enceladus near Saturn, hide colossal oceans of unknown composition under the icy surface.
Building material for DNA
Some astronomers are already confidently saying that liquid water must necessarily be present on the surface or in the depths of rocky terrestrial planets.
Organic compounds are found together with water. So, in the atmospheres of many exoplanets, the simplest and most important organic matter for life, methane, was discovered. In the interstellar space, nitrogen-containing aromatic hydrocarbons can also be found. In principle, these compounds can be the building blocks for DNA or RNA. Traces of simple organic compounds have been found on Mercury, Europa, Ganymede and Enceladus. The study of meteorites that fell to Earth suggests that in the place of their birth - the inner part of the asteroid belt - you can find water ice, nitrogen, sulfur and even sugars with amino acids.
Kepler-22b is the first ever confirmed habitable exoplanet
All this brings us back to the panspermia hypothesis, according to which life was brought to Earth from space. In new developments of this old concept, astrobiologists are supported by cryobiologists, proving that we do not yet know the endurance limits of microorganisms. For example, scientists were surprised by the simplest organisms living in eternal darkness almost a kilometer deep under the Antarctic shield of compressed ice and snow.
Punching wells into sub-ice caverns with water, Antarctic researchers discovered several lakes with extensive microflora and microfauna near the South Pole. These organisms were isolated from the earth's surface for many millennia, but the open strains of bacteria not only survived in the dark ice water, but also successfully developed in ordinary "room" conditions. These studies just coincided with data on the subglacial oceans of some satellites of the gas giants, which bodes well for the search for life under extraterrestrial ice.
Extremophiles
The boundaries of the existence of life are pushed apart in other directions. Organisms that can survive in extreme conditions (biologists call them extremophiles) are found in the ocean depths, arid deserts and salt marshes. Some of them grow even in hot sulphurous waters, which are not inferior in causticity to battery electrolyte.
Extremophile Tardigrades / Tardigrada.
Tardigrades are probably the only animals that can survive on Earth in any situation. They will survive any prolonged drought, the lowest and the highest temperatures, withstand a large dose of radiation and return safe and sound from outer space. No other living creature can do this.
From the depths of the seas and oceans, researchers of extremophiles ascended to the heights of the troposphere. Here, at an altitude of one and a half dozen kilometers, riddled with icy winds and flooded with streams of deadly ultraviolet radiation, there are many types of bacteria. There are even more microorganisms in the dense cloud cover at the top of the troposphere. This is a special world of creatures, and they, like the inhabitants of the ocean depths, will never be able to leave the boundaries of their habitats and touch the surface of the planet.
Astrobiologists claim that the aquatic worlds of the stars are the most attractive places to search for life. Organisms can survive on desert or even Venus-like planets with dense atmospheres. They can also live on colliding asteroids or wandering planets not tied to any star. Liquid water can exist even in the coldest corners of the Universe, on planets heated from the inside through nuclear processes or geothermal activity.
Stream of discoveries
Today, super-powerful terrestrial telescopes compete in the discovery of distant exoplanets with space systems. As a result, every week astronomers discover at least a couple of new exoplanets of the most different types and types. We owe this speed to the discovery of new worlds to the Kepler space telescope. From its launch in 2009 to February 2011, it has discovered 1,235 possible exoplanets, and currently there are more than three thousand.
Undoubtedly, this flood of discoveries is bound to turn quantity into quality someday. And then it will finally become clear what the sensational discoveries of the Martian rover are based on. Maybe it's because the "flooded" space often creates habitable worlds. However, it is very difficult to preserve these pearls of the universe. This is how the seeds of alien flora and fauna perish under the sandy dry winds and streams of destructive radiation, breaking through the remnants of the former atmosphere …
Oleg FAYG