Mars took way longer to form than we thought, ancient impacts reveal

rod

Oct 22, 2019
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Early cosmic impacts may have influenced the evolution of Mars, suggesting that the Red Planet formed much slower than previously thought.

Mars took way longer to form than we thought, ancient impacts reveal : Read more
"To fully understand Mars, we need to understand the role the earliest and most energetic collisions played in its evolution and composition," Marchi said in the statement. "

Energetic collisions is correct. I did not see anything about the original length of day on Mars compared to the present in the model disclosed. The proto-earth in the giant impact model was spinning slowly if at all, after the giant impact, spun up perhaps 2-3 hour day, now spins 24 hours after tidal dissipation of earth-moon system over 4.5 billion years. What was Mars original axis and spin in this model? Late stage planet formation now in the computer models, features very large impactors with high energy and destruction events. Much change in axis tilt and rotation speeds take place, including planets with little or no rotation in the proto-planet stages in the modeling.
 
This is interesting! With this and earlier work we can likely constrain Mars accretion to more or less precisely 10 Myrs after system formation. The paper gives 5-15 Myrs range, but prefers 10 Myrs from average disk dispersal and terrestrial accretion models. (With crust formation within 20 Myrs.) Simultaneously Moon rock dating has been shown to be contaminated and not relevant for dating the system formation, while the Neptune-Kuiper Belt gap as well as inner planet stable formation and Mars + asteroid belt low masses all require an outer system migration within 10 Myrs [ https://www.sciencemag.org/news/2020/01/cataclysmic-bashing-giant-planets-occurred-early-our-solar-systems-history ]. So we have a consistent 10 Myrs Mars formation date where all the many models work.
 
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rod

Oct 22, 2019
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"we have a consistent 10 Myrs Mars formation date where all the many models work."

What about the angular momentum of Mars and length of day? What was the proto-Mars rotation rate and axis compared to the present? The final stages of giant impacts create havoc on axis and rotation rates, this is what the new computer models show. Earth and Mars have similar length of days yet the giant impact for the Moon produces a very fast rotating proto-earth, otherwise we do not have a 24 hour day today on earth. I find many free parameters in the computer modeling reports that indicate quite a few adjustments made to get the various models to work and behave well together :)
 
"we have a consistent 10 Myrs Mars formation date where all the many models work."

What about the angular momentum of Mars and length of day? What was the proto-Mars rotation rate and axis compared to the present? The final stages of giant impacts create havoc on axis and rotation rates, this is what the new computer models show. Earth and Mars have similar length of days yet the giant impact for the Moon produces a very fast rotating proto-earth, otherwise we do not have a 24 hour day today on earth. I find many free parameters in the computer modeling reports that indicate quite a few adjustments made to get the various models to work and behave well together :)
? I was referring to the models I listed that were affected by the formation timeline.
 
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rod

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? I was referring to the models I listed that were affected by the formation timeline.
The link you provided also concluded with words of caution here "The hunt is on for more observations that can parse what happened during those first 100 million years, whether from asteroid samples, clusters of primordial asteroid families, or craters on the Moon and Mars. “Now, the question is, was it a few million years after or 80 million years?” Morbidelli says. “Honestly we don’t know.”

As I read the material, there is quite a bit of reshuffling of the card deck to harmonize different computer models of accretion and collision to make the planets as well as likely different amount of mass in the ecliptic used too. We see this in some differences like Mercury axis tilt and rotation speed, Venus axis tilt and rotation speed, the Earth-Moon angular momentum problem and solution with Earth axis, tilt, and rotation speed, Mars axis tilt and rotation speed, etc. There are also exoplanets with large masses, several jupiters or more that formed well away from the host star compared to our solar system. Continued research will be done :)
 

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