Today our neighbor Mars is a cold, red desert planet. Liquid water no longer exists on its surface due to low atmospheric pressure and temperature. However, there is evidence that streams of a brackish liquid with a low freezing point once flowed along its surface. Water on Mars under modern conditions can be ice, or it can turn into steam, bypassing the liquid state.
Ancient Mars
It turns out that about 4 billion years ago, when Mars was a young planet, its atmosphere was denser, and the surface was warm enough to maintain a liquid state of water, which is a very important condition for the existence of life.
On the surface of Mars, as well as on the surface of the Earth, there are characteristic branched channels that were formed by fluid flows. In the interior of some impact craters, there are pools where lakes once splashed.
The smaller craters disappeared over time, while the larger ones retained signs of erosion. Water destroyed rocks about 3.7 billion years ago. Sediment layers are visible on the crater walls. There are also minerals that could have formed exclusively in the presence of water.
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It is not yet clear whether a favorable climate has been maintained on Mars for a long enough time and whether life has emerged on it during this time.
The earliest signs of terrestrial life are presented in the form of organic chemical structure found in rocks around the island of Greenland. Once these rocks were on the seabed. The structure is approximately 3.8 billion years old, meaning that only 700 million years have passed since the formation of our planet. No fossilized remains of life that date back to this period have yet been found.
Fossils of actual microorganisms are estimated to be 3.5 billion years old. By that time, the conditions favorable for the emergence of life had already disappeared on Mars.
"Comparisons between the histories of the two planets must be made with caution," the researchers warn, "since the chemical composition of the surface of the Earth and Mars is different, as is their volcanic activity."
How did life begin on Earth?
- The Earth appeared about 4.5 -5 billion years ago from cosmic dust and at first was a red-hot ball.
- The ancestor of all creatures living on our planet was named the Last universal common ancestor. He lived about 3.5-3.8 billion years ago. This ancestor cannot be considered the first living thing on our planet.
- There are several hypotheses of the origin of life on our planet, including the hypothesis of spontaneous generation and the hypothesis of the introduction of life from space, including from other planets, for example, from Mars.
- According to one of the most popular versions, life on Earth appeared after there was enough liquid water on it and special climatic conditions developed.
- The first living things were prokaryotes, single-celled creatures without a formed nucleus. These creatures were similar to modern bacteria. Living organisms have evolved and become more complex over millions of years.
- 1000-600 million years ago, there were already jellyfish, molluscs, echinoderms, polyps and flatworms on Earth.
- Having appeared in the ancient ocean, some animals began to gradually get out onto land, while others remained to swim in the water. This happened 416-360 million years ago in the Devonian period.