Ecology: Biology of Interactions. II-15. (supplement) Venus, Earth, Mars

II-15. (supplement) Venus, Earth, Mars
Venus gives us an example of a planet-wide catastrophe.
Carl Sagan
They say that many years ago, a famous newspaper publisher sent a telegram to a famous astronomer: URGENT TELEGRAPH FIVE HUNDRED WORDS IS THERE LIFE ON MARS. The astronomer in good conscience replied: NOBODY KNOWS, NOBODY KNOWS, NOBODY KNOWS... — and so on 250 times.
Carl Sagan
In the process of the formation of stellar systems, part of the matter that forms planets is distributed unevenly. Planets located closer to the star consist of denser substances. In terms of their original composition and properties, Earth is close to its two neighboring planets — Venus and Mars. Mercury also belongs to the terrestrial planets, but this small planet is located so close to the Sun that conditions on its surface have nothing in common with terrestrial ones.
Venus is very close to Earth in size, density, and mass. This planet is located closer to the Sun than Earth. The temperature on the surface of Venus reaches 480°C, and the pressure — 90 atmospheres! Can life exist under such conditions? On the surface of the planet, the existence of complex life on the chemical basis familiar to us is impossible. One could perhaps imagine bacterial life existing in clouds of sulfuric acid at an altitude of 45–60 km above the surface — there the conditions are at least somewhat acceptable. What made the planet named after the goddess of love so harsh? An excess of carbon dioxide, which caused a greenhouse effect!
Mars is very similar to Earth in appearance. Fortunately, we can observe its surface. Conditions on Mars are not so harsh, and several Earth stations operate on its surface. At the same time, it is clear that Mars (more precisely, hypothetical Martian life) has also been unlucky, though not to the same extent as Venusian life. Atmospheric pressure on Mars is approximately 100 times lower than on Earth; the atmosphere consists 95.3% of carbon dioxide, 2.7% of nitrogen, and 1.6% of argon. Oxygen is present only in trace amounts. The diameter of Mars is approximately half that of Earth (0.53), and gravity is 2.5 times lower. The surface area of Mars is close to the surface area of Earth's continents. The temperature on this planet ranges approximately from +25°C to −125°C. Light from the sky falls on the surface of Mars with a significant share of ultraviolet radiation, which is harmful to life. The duration of a Martian day is close to Earth's: 24 hours 39 minutes 35 seconds.
Many generations of scientists have searched for signs of past or present life on Mars. Observation of its surface through telescopes caused an interesting optical illusion: individual spots merged in imperfect optics into stripes, and observers depicted a network of canals, which supposedly covered Mars. In the late 19th century, many believed that industrious Martians had built a planet-wide network of canals to transfer water from the moist polar regions to the dry equatorial ones. One of the first to understand the fallacy of these fantasies was co-author of the Darwinian theory of evolution Alfred Russel Wallace. His calculations showed that the temperature on the surface of the planet was so low, and the pressure so small, that no flowing water could exist on it. In the 20th century, microscopic, rather than intelligent, life was already being sought on Mars.
For the most part, the search for life on Mars has come down to the search for water. According to accepted ideas, at one time this planet was warm and wet enough. Unfortunately, Mars is smaller than Earth and is farther from the Sun. From a certain point on, Mars began to cool catastrophically. The water that formed its oceans is now at rest in the form of ice reserves lying under the surface of the planet, covered by a layer of rock and dust. Evidence for such views is plentiful — from geological evidence (rock formations that could have formed only in liquid water) or consequences of water seeping from below the surface, to traces of ancient oceans.
On the surface of Mars, stripes resembling coastlines were noticed long ago. Astronomers doubted this explanation for their origin. Since these lines ran with changes in altitude, it appeared that in different places the shore and water level were sometimes higher, sometimes lower. However, in recent times, simple explanations have been obtained regarding geological processes as a result of which the altitude of the former shoreline changed. So, 2 billion years ago, two oceans existed on Mars — the Arabian Ocean and Deuteronilus. At that time, sufficiently complex ecosystems formed by prokaryotes existed in Earth's oceans. Did the Martian geological record preserve traces of life from that time? To answer this question, more detailed studies of its surface are needed.
In a meteorite blasted from the surface of Mars, bodies were found that extraordinarily resemble fossilized bacteria. Some changes in the Martian atmosphere (for example, the detection in certain regions of traces of ammonia) can be interpreted as the result of "bio-Martio-chemical" activity of living organisms. In 1976, the American stations Viking 1 and Viking 2 conducted experiments on the surface of Mars designed to detect traces of life. For example, during these experiments, a soil sample was moistened with broth (water with organic compounds) and heated. The decomposition of organic substances in the broth was registered, but whether these reactions were manifestations of microorganism activity or an abiotic process could not be determined. Debates about life on Mars continue to this day...
We can only rejoice that, situated between the "frozen" Mars and the "feverish" Venus, our native Earth provides perfectly adequate conditions for life.