Читать книгу Viruses: More Friends Than Foes (Revised Edition) - Karin Moelling - Страница 28

The Big Bang occurred almost 14 billion years ago. It was the beginning of our universe — not yet of life! Since then the universe has been expanding. 4.5 billion years ago the sun emerged and our solar system arose through asteroids, rocks populating the universe. The rocks and gas gathered under the force of gravity, and its pressure fused them to form heavier elements. They collided and clumped together, forming the planets that circle around the sun. Today, most small asteroids do not survive the passage through our atmosphere and can be seen at night as shooting stars, glowing and dying. Only the bigger ones made it all the way to the surface of our planet. Those asteroids that reached the earth delivered some of the elements known to us from the Periodic Table of the Elements. We are made of “stardust”, which sounds quite poetic.

Timeline of the earth.

Oxygen and iron cannot have been synthesized so easily, just by collision; they needed an energy supply from the explosions of supernovae. I always wonder how iron got into the center of our haemoglobin — our “elixir of life”! As a real curiosity, I keep a piece of an iron meteorite in my Wunderkammer (a collection of curiosities including fossils such as ammonites, shells, petrified trees, amber and corals; unfortunately, I cannot collect fossil viruses, though I would love to do so). The iron meteorite once hit the Campo del Cielo (what a meaningful name!) in the north of Venezuela. The piece of iron is dark and very heavy, so I take it on trust that it is a meteorite (the material on earth arising from asteroids) and that it is really 500 million years old; however, I cannot prove that. Some people think it is magic and can cure diseases — I don’t! Recently I added a can of Coca Cola to my curiosity collection — why? You will see.

We learn the names of the planets at school: Mercury, Venus, Earth, and Mars. Big Jupiter is further away, and its gravity prevented the clumping of asteroids, so that thousands of residual asteroids formed the Asteroid Belt. This belt is called a “habitable zone”, because some scientists expect that there will be extraterrestrial life there. One such asteroid is especially interesting, Ceres, as in 2014 the space agencies detected clouds on it, suggesting it consists of water on the inside surrounded by ice. Water is an essential component of life as we know it today. So could there be life on Ceres? If we could find out, we would learn more about our own beginnings. RNA, viruses, bacteria — that is what I expect and would like to look for.

Where did the Earth’s water come from? That is an interesting and still largely open question. Did “dirty snowballs” like Ceres bring water from extraterrestrial space to our planet, with the dirty dust helping the water to crystallize into ice? Can snowballs be so big as to account for all the water on our “blue planet”, which looks blue from spaceships, because 2/3 of it is water? The astrophysicist Anna Frebel has calculated that each Coca Cola can today contains 5% of fossil water dating all the way back to the Big Bang, 14 billion years ago. I therefore added the drink to my collection of curiosities.

About 4 billion years ago, a star the size of Mars hit the earth and stripped off the moon, at least according to the leading theory. Since then the moon has been drifting away from the Earth by 3.8 cm each year. The moon determines our day and night rhythm, which has increased from 6 to 24 hours. The moon was essential at the beginning of life. Mars is too far away from the sun, while Venus is too close to the sun and therefore too hot. Jupiter is our bodyguard, because it attracts — with its 300 fold greater mass — the debris stones from the Universe and keeps them away from the earth. We have been lucky — so far. There is always the threat that one of these asteroids could hit the earth. In fact, in the year 2029 we are expecting Apophys to hit the earth. Some most recent calculations predict that it will hopefully just miss us!

Life on Earth began about 3.8 billion years go. That was about 10 billion years later than the Big Bang. The crust of the Earth differed in shape from today’s and drifted on top of the Earth’s molten interior. Until today, the tectonic plates have continued to move, and the distance between America and Europe increases by 2.5 cm annually. In Asia colliding plates built the Himalayas, and they are still doing so, causing terrible earthquakes even today. The plates can be detected around the world as the “rings of fire” of active volcanoes. At the contact points between the continents, the bottom of the oceans broke open, volcanoes formed and spouted out magma, which solidified quickly in the water at the bottom of the ocean. From there high chimneys formed, the hydrothermal vents or “black smokers”. Black dust and smoke were released from these volcanoes at the bottom of the oceans. Water there can reach 400°C, because of the high pressure at these depths. Somewhere there, life started. That is almost generally accepted today. In the oceans, 200 meters deep and beyond, there is no sunlight any more, so it is not the sun that supplied the energy: rather, it was chemical reactions that provided the energy for early life. The beginning of life, without sunlight was based on chemical energy production. That was the motor for life. In the opinion of many scientists, it was there that the first biomolecules, such as RNA, arose. The building-blocks of RNA, the nucleotides, are rather complex. How could they have been first, was the counter argument of some scientists. One can imitate their generation in the laboratory today. Only recently a chemist in England, John D. Sutherland, produced all of the three major building-blocks of life (nucleotides for nucleic acids, amino acids for proteins and fatty acids for fat) in a single reaction vessel from very simple ingredients and chemicals: hydrogen cyanide, hydrogen sulphide, phosphate, water (HCN, H₂S, P, H₂O) and energy in the form of ultraviolet light in this case. Some minerals speeded up the multistep “one pot” reaction, as stated by the authors. The prebiotic chemical reactions were supported by zinc and copper as catalysts. Thus, biological material could have formed even all at once. The beginning must have been simple — that is what I believe. This sounds simple.

Hydrothermal vents or black smokers are volcanoes in the deep sea, where life began.