They were born from the same mother, a cloud of gas and cosmic dust composed mainly of hydrogen and helium, with less than 2% of its mass in the form of other elements, among which we could find oxygen, silicon, aluminum or carbon. iron. Elements that, on the other hand, abound in the stones that we see around us, where less than 0.2% of their atoms are hydrogen and helium. The cloud began with a density of only a few thousand particles per cubic centimeter, trillions of times less dense than the air in our atmosphere, tens of times the size of the Solar System to Neptune, and tens of times the mass of Earth. from the Sun. And yet, the cloud very quickly evolved to form a star and several planets in just a few tens or at most a hundred million years. In a time similar to that of the whales on our planet, several worlds were created. Today we know of 8 planets in our Solar System, surely there were or are more, but that’s another story.
They had several supernovae as godmothers, which were surely born from the same mother, pushing part of the original cloud, helping to compress it in these parts and start the process of increasing density in a certain area, right here, and by gravity. it was falling to more and more material to form our Solar System. We know about these supernovae that influenced our birth because they left us rare elements, many of them radioactive, and with strange mixtures that do not go well with what is most abundant on our planets. But that is another story.
They also had a father, what is called a protoplanetary disk, governed by a star in formation, a protostar that would become the Sun, whose temperature was rising until it reached millions of degrees in its center, a few thousand on its surface, and being able to keep the surrounding area warm. Until a distance not much beyond the orbit of Mars, temperatures were above 0 degrees Celsius. At that level, the gas, which we recall accounted for 98% of the mass of the original cloud, was too hot to condense. Neither hydrogen nor helium droplets were formed, but silicate dust specks began to gather, becoming larger and larger by adding iron, magnesium, nickel, or oxygen that oxidized these metals, among other elements. The mixture tended to cool down, but it was also heated by collisions between cosmic rocks, planetesimals that were getting bigger and bigger, which were also hotter in their cores, above 1000 K, something that in recent months we have learned is the point of fusion of many rocks, and that caused the heavier elements to sink and the planets to take on quasi-spherical shapes. But that is another story.
They had cousins, now quite far away, but with whom they may have played in their childhood, either at tag or at throwing stones and snowballs. In fact, without Jupiter we might not have the water we have today. Perhaps because of Jupiter at some point they were closer to the Sun, or perhaps they formed somewhat further away than what we see today, but not much further either, they are rocky planets for a reason and the temperature of the area where they formed could not be very low. If the distances to the Sun were not always the same, perhaps at some point Venus did not receive much more solar radiation than the one that reaches Earth today, or Mars received more, both being able to host liquid water. But those are other stories.
Their common origins must also have meant that their atmospheres were very similar early in their evolution. They were so hot that no gas could be trapped by the gravity of each planet, it escaped into space, so the large amounts of hydrogen or helium in the parent cloud never made it into a large atmosphere. That was indeed the case of planets like Jupiter or Saturn, which have atmospheres that are called primary, and they were able to grow much more by being able to feed on the superabundant hydrogen and helium. The planets closest to the Sun, as they gradually cooled on the outside and kept warm inside, released gases that formed secondary atmospheres. The similar composition of the 3 planets surely meant that these atmospheres were very similar in their origins, a combination of the gases normally released by volcanoes: water, carbon and sulfur dioxide, or methane. In fact, in the Earth’s atmosphere when it was less than half today’s age, around the transition between the eon archaic and the proterozoic, surely sulfuric acid clouds abounded like those on Venus today. There are more stories there that would explain why our air is “nitrogen, oxygen and argon”, as Mecano sang to us.
We conclude now. We have 3 sister planets whose origin is common, which makes Venus, Earth and Mars called rocky, terrestrial or inner planets. Their internal composition is not very different, dominated by iron, magnesium, silicon, oxygen… But at some point they began to separate their destinies. Today their atmospheres are tremendously different, perhaps because they have other notable differences, such as the distance from the Sun, the presence of a strong or almost non-existent magnetic field, different rotation periods, or more or less large or absent satellites. The fact is that only one came to evolve to give rise to something that today we cannot get rid of considering unique, because we have not seen it anywhere else: life. Why Earth? Was I destined for it? Destined to harbor life or to maintain it? Did the other rocky planets once harbor life? Is there something that tipped the balance towards being inhospitable planets versus one full of life? Or was it a combination of factors? Are there many factors that must conspire in a planetary system for life to appear? How likely is that life event? Is the universe big enough and old enough that, however low that probability is, it is impossible that there is no life beyond our planet? Those are other stories, most of them never written, not even conceived.
Pablo G. Perez Gonzalez He is a researcher at the Center for Astrobiology, dependent on the Higher Council for Scientific Research and the National Institute of Aerospace Technology (CAB/CSIC-INTA).
cosmic void it is a section in which our knowledge about the universe is presented in a qualitative and quantitative way. It is intended to explain the importance of understanding the cosmos not only from a scientific point of view but also from a philosophical, social and economic point of view. The name “cosmic vacuum” refers to the fact that the universe is and is, for the most part, empty, with less than one atom per cubic meter, despite the fact that in our environment, paradoxically, there are quintillion atoms per meter cubic, which invites us to reflect on our existence and the presence of life in the universe. The section is made up Pablo G. Perez Gonzalezresearcher at the Center for Astrobiology; Patricia Sanchez Blazquez, full professor at the Complutense University of Madrid (UCM); and Eve Villaverresearcher at the Center for Astrobiology.
You can follow MATTER on Facebook, Twitter and Instagramor sign up here to receive our weekly newsletter.
#planets #destination