Venus' Strange Rotation Was Likely Triggered By a High Velocity Moon-Sized Impactor (universetoday.com) 27
New simulations suggest Venus' extremely slow backward rotation may have been triggered by a high-angle collision with a fast-moving object roughly one-tenth its mass. The impact could have dramatically altered Venus' spin and melted nearly its entire mantle. Universe Today reports: Venus' bizarre and extraordinarily slow retrograde rotation on its axis has long puzzled planetary scientists. But in a new paper presented at the recent European Geosciences Union General Assembly in Vienna, the authors argue that their models indicate that a high angle moon-sized, high-velocity impactor likely triggered Venus's strange 248-day rotation. And it probably happened within the first 50 million years of Venus' formation. [...] The team found that an impactor that is about a tenth of Venus' mass hitting the planet at a high angle could drastically slow the early young planet's rotation.
Depending on the actual impact parameters, we can slow down a rapidly rotating early Venus to rotation rates that are that are compatible with long-term evolution towards a slow rotating planet, says [Cedric Gillmann, the paper's lead author and a planetary scientist at ETH Zurich]. Or even in some cases with large energetic impact that happen with a tangential impact that would even put planets early on in already a retrograde but faster rotation, he says. In the simulations, giant impacts expectedly produce surface magma oceans, the paper's authors note. Their relative depths vary depending on impact properties: from a shallow melt layer in the order of 100km thick to a fully molten mantle, they note. If the surface can radiate heat to space efficiently, the magma ocean cools down quickly, they write.
If Gillmann and colleagues are correct, Venus' likely impactor also melted some 99 percent of Venus' mantle. That is, the interior structure that extends between its core and crust. You will get rid of that impact heat pretty efficiently, and after a few hundred million years, you end up seeing an evolution that is very difficult to distinguish from a case where you don't have an impact, says Gillmann. What role the impact may have played in Venus' lack of plate tectonics, however, remains open for debate. But it's known that Venus' lack of a large-scale carbon recycling mechanism likely led to its current runaway greenhouse.
Depending on the actual impact parameters, we can slow down a rapidly rotating early Venus to rotation rates that are that are compatible with long-term evolution towards a slow rotating planet, says [Cedric Gillmann, the paper's lead author and a planetary scientist at ETH Zurich]. Or even in some cases with large energetic impact that happen with a tangential impact that would even put planets early on in already a retrograde but faster rotation, he says. In the simulations, giant impacts expectedly produce surface magma oceans, the paper's authors note. Their relative depths vary depending on impact properties: from a shallow melt layer in the order of 100km thick to a fully molten mantle, they note. If the surface can radiate heat to space efficiently, the magma ocean cools down quickly, they write.
If Gillmann and colleagues are correct, Venus' likely impactor also melted some 99 percent of Venus' mantle. That is, the interior structure that extends between its core and crust. You will get rid of that impact heat pretty efficiently, and after a few hundred million years, you end up seeing an evolution that is very difficult to distinguish from a case where you don't have an impact, says Gillmann. What role the impact may have played in Venus' lack of plate tectonics, however, remains open for debate. But it's known that Venus' lack of a large-scale carbon recycling mechanism likely led to its current runaway greenhouse.
Plate tectonics? (Score:2, Interesting)
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Tidal forces do exist on Venus because of the sun. In fact it's stronger than the sun's pull on Earth because Venus is closer.
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It seems you're right - https://www.brown.edu/news/202... [brown.edu]
https://www.reddit.com/r/space... [reddit.com]
'Venus is still wet' (Score:1)
Oh, behave!
Moon-sized impactor (Score:2)
How big is a moon?
(Take a look at the objects orbiting Saturn and Jupiter)
Or even the moons of Pluto (Of course it can't have moons since its not a planet)
Plutos Revenge. (Score:5, Funny)
Or even the moons of Pluto (Of course it can't have moons since its not a planet)
Pluto is smiling. Devilishly.
Pluto remembers the last time Trad Universe tried to snatch a planet card away from a gravitationally-challenged body. His distant cousin came flying in and s-lammed into this big fucker. Heard he hit it so hard it saw stars and rings.
Nobody picked on dwarfs for a long time after that. Until recent times.
Jupiter, might want to keep an eye open.
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They likely meant Moon-sized instead of moon-sized.
They could have used Luna-sized, which would have been unambiguous but somewhat obscure.
Another option (that'll get snarled in spellcheckers): TheMoon-sized.
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So, half a Cowboy Neal?
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Don't know, but the headline says "Moon", not "moon" even if TFA lowercases it. And TFA says "strange 248-day rotation", which only makes sense if you assume they mean Earth days, not Venusian or days of any other planet. So I would assume you're supposed to use Earth equivalents as a reference, which is what you'd expect for something written for a general audience, not an audience of nit pickers ;P
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It's the number of earth days it takes to rotate around its own axis, not around the Sun. So one Venus day = 248 Earth days, one Venus year is 225 Earth days. Yes, Venus has a day that's longer than its year.
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" As a result, a Venusian day is 116.75 Earth days long, about half a Venusian solar year, which is 224.7 Earth days long."
I am reasonably, but not entirely, confident that Wikipedia is reliable in this. It's not always correct.
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Maybe someone hacked it and someone else corrected it? This text is in Wikipedia right now:
> Venus has retrograde rotation, meaning that unlike most planets, including Earth, it rotates clockwise around its own axis, opposite to its anticlockwise rotation around the Sun. Therefore, Venusian sidereal day, 243 Earth days, lasts longer than a Venusian year, 224.7 Earth days.
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True. But at least when it is incorrect, it's authoritatively incorrect.
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Don't know, but the headline says "Moon", not "moon" even if TFA lowercases it.
The fact that the article uses lower case would tend to suggest that "moon" is correct. Title-case would capitalize the word in either case, so it isn't useful for inference.
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Other planets don't get days, because they don't have people. They just get rotations.
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How big is a moon?
(Take a look at the objects orbiting Saturn and Jupiter)
Or even the moons of Pluto (Of course it can't have moons since its not a planet)
Pluto is still a planet. It's been termed as a dwarf planet, which is still a type of planet.
(It should still be one of the major planets, but that's another discussion)
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3,474km in diameter, but really it's not the size that counts, but the mass (and how you use it).
Or, hear me out... (Score:2)
It is a hypothesis that explains the present evidence about as well as their proposed hypothesis. Sure, they can run a numerical simulation and say "hey, this could have messed with Venus' rotation". I also can calculate angular momenta. But is there anything testable to come out of this? Is there any evidence we could spot today that favors the impact hypothesis over some other one?
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Why not go with Cthulhu?
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Why not go with Cthulhu?
Cthulhu has no interest in planetary bodies other than what creatures may exist on it that can be mentally manipulated into observing its non-quantifiable visage and teetering their mental capacity into the non-standard state that humans refer to as insanity.
The Flying Spaghetti Monster is filled with benevolence and kindness, as well as the quest to consume all knowledge, so that he may impart said knowledge with his noodly appendage upon all who dare to believe in his greatness.
Re: Or, hear me out... (Score:2)
(With apologies to Sluggy Freelance.)
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It is a hypothesis that explains the present evidence about as well as their proposed hypothesis.
A lot of slashdotters really seem to misunderstand science, how it works and what it does.
No, the FSM does not explain the evidence "about as well", because there's zero evidence for the FSM, but there's considerable evidence for the presence of somewhat denser rocky bodies in the early solar system and collisions between them.
Bumper cars common back then? (Score:1)
Being Earth was also alleged whacked by a Mars-sized object, forming our moon, it seems colliding spheres is common during the early stages of planetary systems. The difference is we got a terrific silvery moon out of it, but Venus only got long nights.
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Not only common, but necessary.
Planets don't just spring into being. They form through gradual accretion, and that is not constrained to just one big thing eating all the other little things. Its a bunch of little things all eating littler things, getting bigger in the process, and then colliding with each other as their orbital mechanics change from the changes in mass and angular velocity/momentum.
Most models have things forming in the outer solar system and falling in, as they get heavier and slower-- o