If we look at the planets and moons of our solar system today, it would be very easy to be fooled into thinking that everything always looked like this. But in recent years scientists have learned to their surprise that the solar system used to look very different. Below we will list some of the shocking discoveries that show how a series of violent events have shaped our solar energy into what we see today.
1. When Theia hit the earth
The question of how the moon was formed has long been an argument among astronomers, but the evidence of recent years points to a dramatic answer: that it was formed by a direct collision with the earth by another planet.
The Giant Impact Hypothesis states that within the first 100 million years after the formation of the Earth (4.5 billion years ago), a planet near the size of Mars suffered from it.
Known as Theia, this small planet was completely erased by the collision. The earth did not do much better, with an enormous amount of material thrown away by the impact – material that would someday reform and cool like the moon.
The theory may sound far-fetched, but it now has regular approval, with evidence for this amazing encounter with every study.
2. The late bombing period
We know that the formation of the early solar system must have been a violent place, filled with rocks and debris flying everywhere. The most dramatic proof of this comes from the countless craters observed on every planet, moon, even asteroid, in the solar system.
All the more so because each of these bodies demonstrates that they have all formed and cooled sufficiently before the blows started.
Known as the Late Bombardment Period, this would have occurred around 4 billion years ago, and was effectively caused by leftover debris from the formation of the solar system that was flung around like pinball machines.
As various craters prove, it was a particularly violent period. In the beginning it was not clear what could have caused this sudden bombing, but we now have an idea …
3. Nice five-planet model
For a long time, no computer model of the formation of our solar system has led to the ordering of planets that we see today. That was a mystery, because the overall process of planetary formation is something that we can observe around other stars.
An amazing solution, proposed by a group of astronomers in Nice, France, in 2005, is that the planets that we see now did not form in those positions, but drifted there over time. If that's right, the Nice model would certainly explain why the Late Bombardment period took place.
But it goes beyond that: the most recent version, Nice-V, claims that the solar system used to have an ice giant planet, which was thrown out of our solar system by the movements of the other giant planets.
If it all sounds far-fetched, the problem is that math really works. To date, it remains the only computer model of the solar system that actually predicts the positions of the planets as we see them now.
Strangely enough, even the Nice models have nothing to say about the supposed Planet Nine, which means that the Nice models are wrong – or that Planet Nine, if it exists, might have been captured from another galaxy.
4. Roaming Jupiter
The evidence to support the Nice model continues to increase. This week a study published in Astronomy & Astrophysics published how Jupiter may have been moved in the early solar system. Their conclusions are striking.
According to the study by Lund University, Jupiter originally formed a trajectory four times as far from the sun as it is now. For a period of less than a million years, Jupiter migrated inwards to his current job.
Apart from everything that has been discussed so far, there is striking evidence for this from Trojan asteroids, who share the orbit of Jupiter. There are two different groups, and computer models show that they must have been picked up while Jupiter roamed to its current position.
We will learn more about this because NASA will soon launch a space probe named Lucy to analyze these Trojan asteroids.
5. When a planet collided with Uranus
A strange feature of Uranus is that the planet actually turns on its side compared to the other planets in the solar system. This is impossible to explain in the normal way. The only viable alternative is a collision theory.
Originally it was suggested that a comet would have collided with the gas giant, but more recent models suggest that something much bigger would have been needed to knock Uranus so completely on its side – twice the size of the Earth.
Computer modeling by astronomers at the University of Durham published a study last July suggesting that a proto-planet, largely consisting of rock and ice, hit Uranus about 4 billion years ago. This may have happened while the giant planets were still moving through the solar system, according to the Nice model.
However, this collision theory adds an interesting new twist: the impact of the collision effectively stifled Uranus' core, preventing heat from reaching the outside atmosphere, and thus explaining why Uranus has what an otherwise inexplicable cold surface temperature is.
6. When Neptune conquered Triton
It is not only the planets that have moved within the solar system. Research now suggests that Triton, the largest moon around the planet Neptune, did not originally form there.
The most important evidence that points to this theory is that Triton revolves around Neptune in a retrograde movement. In fact, it is deteriorating compared to all other moons of Neptune.
Computer modeling has since shown that Neptunus could indeed have caught Triton, especially while the gas giant, along with the other giant planets, migrated through the solar system to its current position.
7. Mercury in collision?
Planetary collisions may seem like a rare and extraordinary event, and yet we have another possible scenario in the form of Mercury.
Simply put, Mercury is so unusually dense that it resembles something more like a planetary core than a planet. But if so, where is the rest of Mercury?
Although Mercury is very close to the sun, heat and solar winds alone are not enough to remove the outer layers of Mercury. Computer modeling suggests that a huge impact by another small planet might have created what we see now.
However, this theory is not clear. The biggest problem is, if something struck Mercury, where did the rest go?
8. Phaeton – the planet that never was?
A popular theory in the 18th century saw a pattern in the order of planets. Later known as the Titius-Bode law, it successfully predicted the position of Uranus, although it could not predict the position of Neptune.
Part of the series, however, fell on the asteroid belt. Some early astronomers thought that this meant that there was a planet there, but somehow it had been destroyed – perhaps by Jupiter's gravity.
The idea fell out of favor, and now conventional science believes that the asteroid belt is only a remnant of the formation of the solar system.
There are two curious reasons why we will see more discussion about this.
The first is that the asteroid belt consists of two main groups of different asteroids with a very different composition. The second is that one of the most massive asteroids there, 16 Psyche, gives every suggestion to be a small planetary core.
Is it possible that the asteroid belt was formed by the collision of two small planets? We will soon find out that NASA will soon launch a probe to explore the asteroid belt and in particular 16 Psyche.
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