Dipl.Ing. NT , Astrophysiker
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You don’t drink before life !…….After maybe ?
I like to watch the gradual emergence of life and participate in it diligently. The emergence is a bit like preparing for a desirable celebration.
What must be present and what do I need?
The planet needs solid ground, plenty of liquid, usable oxygen and sufficient energy through nutrition. No matter what is to live there, it should take place on the good planet Earth.
How do we get solid ground under our feet? First I will look at a gaseous planet, because the process is similar to that of the sun. Gas condensations form in the sun, or more generally in a disk around the sun, they collapse under their own weight and with their growing gravity they draw more and more gas towards them. To put it somewhat humorously, the formation of gaseous planets is a very short-term story, …….., i.e. a little longer than a few hundred thousand years.
Let me now turn to the rocky planet Earth and take a look. The first thing to mention is that considerably more time passes. This is because at the beginning the smallest dust particles collide, these become more and more strongly connected with each other, and as a result further clumps of particles are drawn towards them. The so-called structure continues to grow bit by bit due to enormous asteroid traffic. Until finally, and in the end, a rocky planet is formed. This could possibly take more than 100 million years. This is also what happened with the inner planets in the solar system: Mercury, Venus, Earth and Mars.
The topic of liquid has been reached. We need enough watery liquid for our celebration. Question: How does a planet get enough water? It should be noted that Mars and Venus have „no“ water, they are just dry as dust.
Now we need to clarify why Earth, of all planets, has so much water? Well, I’ll let the explanation follow.
Let’s take a look at the position of the planets in relation to the sun.
But please be a little more precise.
My first statement is: for the possibility of biological life, I only see a certain and therefore healthy, excellent area around the star (the sun)
If a planet orbits too close to the sun, it is too hot for life. If it is too far away, it is too cold. Simple or ?
If the planet is moving in the zone predestined for life, the „habitable zone“, but not too fast now, watch out !!!
Then this circumstance has not per se or naturally endowed it with water. We now know that originally there could not have been any water in the habitable zone. This is because the space between a star and the surrounding dust-gas disk, in which planets form, can be divided into two areas, which were defined by a boundary line, the so-called snowline. In the outer, i.e. cold area, water occurs „if at all-only frozen“; and what about the inner area? In the inner region around the parent star, i.e. the sun, water can only occur in the form of vapor due to the high temperature and therefore evaporates immediately. This is why all planets in the habitable zone around a star are initially dry, even dust-dry. Are you wondering? … or are you starting to ponder?
No wonder, because the Earth appears beautifully blue to you, and of course this is clearly due to the abundance of water. So there is only one reason for this. That’s right, the water must have been brought in from outside…….
……and that’s the case and it’s true!
Carbonaceous chondrites are a certain type of asteroid and meteorite. You probably already know them from a previous chapter. They are very special stones, they are said to be the least altered material from the first days of the solar system. Some of them, or rather quite a few, contain water. It is the ratio of deuterium, the heavy hydrogen isotope, to hydrogen that tells us where the water originally came from. My colleagues and I say that it came naturally from the gas cloud and the dust from which the sun was formed.
I notice that there is water in practically all gas clouds in the interstellar medium. And if the dust particles that are certainly present have already condensed into asteroids, then you’re dealing with actual rocks that bring water with them when they’re about to crash into a forming planet. On the other hand, and also possibly, some of our water was also brought in by comets. The ratio of deuterium to hydrogen that I mentioned earlier is practically like a fingerprint that only a few comets, but most asteroids and meteorites that fly around somewhere between Jupiter and Mars, give off. So there is every indication that the Earth was supplied with water by planetoids. Three to four impacts could have been enough to supply water. For some years now, we „astros“ have had clear evidence that liquid water already existed on our planet around 150 million years after the formation of the Earth. It is also interesting to know that zircon crystals have been found in the Jack Hills in Western Australia that are, believe it or not, 4.4 billion years old. The oxygen-isotope ratio in the crystal points to liquid water at the time of its formation. Actually very surprising. The Earth was still young at that time and liquid through and through, i.e. totally liquid. Is there supposed to have been liquid water back then? My answer to the question is yes, and I say that if the pressure in the atmosphere is high and the earth’s crust is already rigid, then it works, and water remains liquid even at higher temperatures. We also know for sure how the story must have continued. As I have already said, if the Earth was still largely molten more than 4.5 billion years ago, the water evaporated again immediately. However, since the young planet already had enough mass, its gravitational pull was sufficient to maintain this first, humid atmosphere. In fact, it must have been so dense that the moon, which had already formed only 60,000 kilometers away at the time, could not have been seen. There was also a lot of carbon dioxide, methane, ammonia and much more, so it is safe to say that this atmosphere was more like that of Venus today: almost 100 percent carbon dioxide. What happened next and what happened next? The Earth began to cool very slowly. So slowly that the temperature of the Earth’s core today is still as high as the temperature of the sun at its surface, i.e. around 6,000 degrees Celsius. So where do we stand now in preparing for our upcoming celebration? We have carbon dioxide, water vapor and a planet that is still churning under the cooling crust. The internal heat source affects what happens on the surface. It causes bottom-up convection currents that keep the lithosphere – the Earth’s outermost crust – in constant motion. The crust literally floats on a molten mass of rock. But where does this enormous heat come from? We know that today half of the residual heat comes from impacts and the other half from radioactive decay. In the past, of course, radioactive decay was far more important. To summarize, we can say that there was a lot going on on the young Earth. An atmosphere of carbon dioxide, water vapor, methane and many other gases spewed out by countless volcanoes and large-scale, glowing masses of rock. But please note, dear reader, there was no oxygen in the atmosphere yet, and no nitrogen either.
Here is my brief summary. The „Earth“ has one source of energy, it is its inner heat. An extremely dense atmosphere, with almost perpetual thunderstorms and downpours, because there is water, liquid and gaseous. There are movements of the earth’s surface and gigantic volcanism. All the ingredients for the party I mentioned at the beginning are ready, now it’s just a matter of getting everything together in the right proportions, and I’m keeping a lid on who’s doing that. A very special cocktail of life is now waiting to be served. ……After this easy-to-learn list and description, I finally feel comfortable saying: „Dig in, readers“ !!!‘