Drama in the early outer Solar System

[lpetrich]

The Moon was most likely the result of a collision between the early Earth and a Mars-sized object, and I've seen similar giant impacts implicated for Mercury and Mars. But there was also plenty of drama llama in the early outer Solar System.

Young Jupiter was smacked head-on by massive newborn planet noting
The formation of Jupiter’s diluted core by a giant impact | Nature

The Juno mission has measured Jupiter's gravitational field to much greater accuracy than previously, and that has increased how much one can constrain its interior density profile. This has led to a remarkable result:

A colossal, head-on collision between Jupiter and a still-forming planet in the early solar system, about 4.5 billion years ago, could explain surprising readings from NASA's Juno spacecraft, according to a study this week in the journal Nature.

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Liu said the calculations included estimates of the probability of collisions under different scenarios and distribution of impact angles. In all cases, Liu and colleagues found there was at least a 40% chance that Jupiter would swallow a planetary embryo within its first few million years. In addition, Jupiter mass-produced "strong gravitational focusing" that made head-on collisions more common than grazing ones.

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"Because it's dense, and it comes in with a lot of energy, the impactor would be like a bullet that goes through the atmosphere and hits the core head-on," Isella said. "Before impact, you have a very dense core, surrounded by atmosphere. The head-on impact spreads things out, diluting the core."

Impacts at a grazing angle could result in the impacting planet becoming gravitationally trapped and gradually sinking into Jupiter's core, and Liu said smaller planetary embryos about as massive as Earth would disintegrate in Jupiter's thick atmosphere.

"The only scenario that resulted in a core-density profile similar to what Juno measures today is a head-on impact with a planetary embryo about 10 times more massive than Earth," Liu said.

New Timeline for 'Giant Planet Migration' May Rewrite History of Our Solar System | Space
Onset of Giant Planet Migration before 4480 Million Years Ago - IOPscience

The largest planets in our solar system could have drifted away from the sun much sooner than scientists previously thought, a new study suggests. Understanding this phenomenon could help researchers to explore the origins of life on Earth.

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These researchers estimate that a phenomenon known as "giant planet migration" happened much earlier than previously thought. This "migration" is a stage in the solar system evolution when the largest planets started to move away from the sun.

It is "a concept wherein Jupiter gravitationally affects the orbits of the outer planets Saturn, Uranus and Neptune. And, by this mutual, gravitational effect, the four giant planets each migrate and this migration leads to a small inward movement of Jupiter towards the sun and a systematic outward orbital position for Saturn, Uranus and Neptune," Mojzsis said to Space.com. This event affected the orbits of objects in both the inner and outer solar system.

The researchers conclude that this event happened around 4.48 billion years ago, well before earlier estimates.