Thick atmosphere boosts how fast Venus spins

Posted: July 23, 2018 by oldbrew in atmosphere, research, solar system dynamics, wind
Tags: ,

Venus


The apparent length of day on Venus (116.75 days) is nothing like its rotation time (~243 days), due to its retrograde spin. It can be stated as the time in which the sum of the number of Venus orbits (~0.52) and spins (~0.48) in the period equals 1.

As ScienceNewsforStudents reports, the thick atmosphere on Venus can change by a few minutes every day how long it takes the planet to rotate.

Time gets tricky on Venus. The planet has extremely thick air, which flows much more rapidly than the rate at which the solid planet spins.

As that thick atmosphere pushes against the planet’s mountains, it can change how quickly Venus spins, scientists now report.

Researchers used a computer to simulate the movements of that thick atmosphere. It whips around at 100 meters per second (around 224 miles per hour). Those winds exert enough push against mountains on one side of the planet — and suction on the other side — to alter the speed of the planet’s rotation. The thick atmosphere increases the rotation rate by up to about two minutes each day. Each Venus day, that is. And each day on this planet is 243 times longer than one on Earth.

Two minutes is not much in a rotation that lasts almost 350,000 Earth minutes. Venus’ atmosphere, by contrast, rotates about once every four Earth days (5,760 Earth minutes).

There also must be some other force slowing the planet’s spin back down. If not it would continue to just spin faster and faster. What might that other force be? Researchers suspect it could be the sun’s gravitational influence.

The researchers reported their calculation in the July issue of Nature Geoscience.

Then there’s that mighty wave

Precise measurements of the rotational period (day length) on Venus have varied by up to seven minutes. The push and pull of the air over the planet’s mountains could help explain this mismatch.

Thomas Navarro and his colleagues wanted to better understand the differences in the planet’s spin. Navarro is a planetary scientist at the University of California, Los Angeles. He was part of a team that developed the computer model to study the thick Venusian atmosphere and how it affects the planet’s spin. Their results are the first to explain a bizarre wave found atop the planet’s clouds. That wave is 10,000 kilometers (6,200 miles) long, extending from pole to pole.

The Japanese space agency’s Akatsuki spacecraft first spotted that wave in 2015. Similar waves ripple through Earth’s atmosphere when air flows over a mountain. But those Earth waves normally dissipate quickly. Opposing winds break them up. Not so on Venus. Its atmosphere rotates far faster around the planet — and in only one direction. So once formed, such waves can persist for a long time.

Continued here.

Comments
  1. P.A.Semi says:

    Venus is in double resonance with planet Earth, and it is one of best fitted resonances in Solar system.
    The orbits resonate 13:8 , each 13 Venus years is 8 Earth years, with a difference of few days (do I remember correctly 2.5 days?), which makes the resonance pattern rotate by one fifth of the circle once in some 250 years, full round something more than 1100 years… (Musical chord of this resonance is sexta minor)

    Then, Venus spin resonates with Earth orbit 12:8. Each 12 Venus days are 8 Earth years.
    Every time Earth and Venus meet, Venus points a same face toward planet Earth. Every time they are in opposition arround Sun, Venus points that same face toward Earth and Sun. Hence it seems, that Venus is tidally locked by planet Earth, not only by Sun (as is a case with Mercury).
    I somehow doubt, that winds change Venus spin more than little in longer perspective…

    Earth orbit is little irregular due to pulls from large planets, but resonance with Venus stabilizes the irregularities back to a common pattern. If one planet is too soon to the meet-point, the other pulls it back and slows it down, if it is too late to the meet-point, the other pulls it ahead and speeds it up. (This can be seen, when studying frequencies of 8-year meet-point time distances in JPL ephemerides, that irregularities in the 8-year frequency soon fade out and level) This way, our orbit is much better stabilized than for ex. Mars orbit, which shows higher irregularities. And making the resonance double (orbit and spin) prevents both planets to travel out together toward Jupiter. Stabilizing orbit time stabilizes orbit distance, due to Kepler laws. (I conjecture, that some of Milankovitch cycles are vibration arround optimal resonance with Venus?)

    It (this double resonance) is one of signs of Intelligent Design of Solar system. (Which is why scientists are fearing to admit the resonances)

    The other such sign of Intelligent Design is, that Moon orbit is tuned to Sun spin, which makes Earth pulse on it’s orbit in and out synchronized with Solar spin, which, by my opinion, helps to recharge Earth’s magnetosphere, that has been speculated, that it should have been long since faden away like on Venus and Mars, but surprisingly it is not… Solar spin is highly irregular, faster on equator and slower on poles, and arround latitude 40° it is synchronized with Earth-Moon pulse, and from this latitude each sunspot cycle starts toward equator – is it just a coincidence…?

  2. oldbrew says:

    @ PA Semi

    Interesting stuff. 12:8 = 3:2 i.e. first order resonance.

    Re sunspot cycles, there is evidence that Earth’s auroras are linked to them, especially around solar maximum. Auroras are known to be more prominent around the time of the equinoxes, i.e. March/April and September/October.

    See Figure 2 here:
    http://www.scielo.org.mx/scielo.php?pid=S0016-71692011000400006&script=sci_arttext

    New clues to possible Venus auroras
    http://earthsky.org/space/new-clues-to-possible-venus-auroras
    – – –
    Also, see first link under ‘Related’ at the end of the blog post.

  3. oldbrew says:

    As PA Semi noted above:

    With a little arithmetic (taking inverses) we can easily convert that value to the rotation period with respect to the Sun or, in other words, to the day on Venus. It is 116.75 (Earth) days. Five of those periods equal 583.75 days, which is almost the same as the 583.92 day synodic period. So each time the planets line up Venus shows almost the same face to the Sun and hence the same face to the Earth, which is always on those occasions on the opposite side of Venus.

    From: Are transits and the rotation of Venus linked?
    https://tallbloke.wordpress.com/2017/09/28/are-transits-and-the-rotation-of-venus-linked/

    Also in that link we added some notes…

    Note 1: 23 solar rotations @ 25.38 days = 583.74 days
    This also looks like a resonance, this time between the Sun and the Venus day.
    – – –
    And so, astronomers have decided to measure the rotation rate of the Sun from an arbitrary position of 26° from the equator; approximately the point where we see most of the sunspots. At this point, it takes 25.38 days to rotate and return to the same spot in space.
    http://www.universetoday.com/60192/does-the-sun-rotate/

  4. oldmanK says:

    P A Semi’s post above is of particular interest (but short of needed understanding on my part). Tks.

    Question: My target is the Eddy cycle (980y); its origin. Wiki says Earth Venus resonance is 1000y. See table in Link: https://en.wikipedia.org/wiki/Orbital_resonance .

    P A says 1100yrs. Any more light here please?

  5. P.A.Semi says:

    My work on resonances, published in 2009, was also somehow discussed here… On first 8 pages it discusses Earth-Venus relationship, there is even the chart of 8-year frequency showing orbit irregularities…

    http://semi.gurroa.cz/Astro/Orbital_Resonance_and_Solar_Cycles.pdf

    (There’s just no wording of “Intelligent design” yet…)

    It also shows, that there is not a sharp pentagram, but rather an oblique rosette-like shape.

    [img]http://semi.gurroa.cz/Astro/EVBary_1902-1910_Bold.png[/img]

    And I also detected a 243-year cycle, not a 251 year one, as stated in the linked article above…

  6. P.A.Semi says:

    re oldmanK:
    About 1100 years: I’ve written this from my faint memory. In my work (pdf link above) there is 1199 years for full turn of the meet-point shape, but since the shape is made of 5 symmetric meet-points, to rotate it one fifth of circle takes 243 years.
    (The numbers do not add up? 243*5-16=1199…)
    I’m at this moment somehow lazy to verify my own old claims…

    About wiki/Orbital_resonance – I’ve tried and abandoned to add the mention of these resonances back in 2009, it was actively censored. Only some time later someone added the paragraph about “Coincidental ‘near’ ratios of mean motion”, which contained thesis, that these “have no dynamical significance”.

    My chart of 8-year frequency irregularities being damped out to restore regular rate proves different, it is of quite high dynamical significance to Earth orbit…
    (in the PDF linked above, it is Figure 4e…)

  7. oldbrew says:

    Ian Wilson commented on the 251 year period here, and the figures and explanation are in the related post.
    https://tallbloke.wordpress.com/2015/07/03/why-phi-a-venus-transit-cycle-model/#comment-103293

    The data is from NASA.

    Re Wikipedia, the ‘gatekeepers’ there don’t seem to want any planetary ideas except their own to get any attention.
    But the Venus transit page is still quite interesting.
    http://en.wikipedia.org/wiki/Transit_of_Venus#Conjunctions

  8. JB says:

    “There also must be some other force slowing the planet’s spin back down. If not it would continue to just spin faster and faster. What might that other force be? Researchers suspect it could be the sun’s gravitational influence.”

    It would be useful to identify what force causes a planet to rotate in the first place. Inertia, defined as the ratio of gravitational force versus equatorial acceleration, is highest for Venus among all the planets. It is nearly 57K times that of Earth, and nearly 7 times that of Mercury. Saturn has the least, having the largest volume to mass ratio of any body in the solar system including the Sun. Conversely, Mercury, Venus and Earth all have a volume to mass ratio very close to each other. The ratio of rotational velocity versus gravitational force of Venus is also highest among all the planets.

    What this suggests is that Venus is the densest of all the planets, its mass being composed of heavier atomic elements, and such elements tend to resist the force causing rotation.

    It is erroneous to say that the planet would spin faster and faster, absent a counter force. No body being driven to rotate will do so at a rate faster than the velocity of the driving force.

  9. P.A.Semi says:

    Inertia makes the planets rotate. The original dust-cloud, from which solar system formed, was rotating, and while contracting to a planet, the preservation of angular momentum makes the rotation faster.

    Then there does not need to be any other force to sustain rotation. The mass itself does not resist rotation, just to make rotate heavier mass requires more angular momentum. Venus is not that much heavier, how much slower it rotates, it had to be braked down.

    Adding external heat causing clouds to transfer angular momentum to hills and planet body can probably speed-up the rotation, though. After all, conservation of energy including conservation of angular momentum requires, that speeding or slowing of rotation must bring some energy in or out (or change mass distribution), and considering adding Solar radiation energy, that would not be radiated away all, converting to spin angular momentum is probably not that far-fetched.

    About Venus velocity (you write: “No body being driven to rotate will do so at a rate faster than the velocity of the driving force.“) – driving force of clouds said above to rotate in 4 earth-days is sufficiently higher than ground velocity of 243 earth-days, so this condition holds.

    But as I’m convinced, that the 12:8 resonance of Venus spin with Earth orbit is not a momentary coincidence, hence Venus does not speed-up on longer terms. Probably tidally locked – by Earth?

    Magnetism could slow-down (or possibly speed-up? rather not in this case) rotation by transfering angular momentum to another body. (I’m convinced, that solar poles are magnetically braked by magnetic-line connection with biggest structure in solar system – the solar wind plasma, turning it to a Parker spiral…? Also all planets move retrograde from solar-surface point of view, so could be solar poles magnetically braked by planets…? Tidal effects would be higher pronounced near equator, while magnetic effects would be higher pronounced at poles… All planets move retrograde (slower) from faster spinning solar surface view, with Mercury moving slowest… What else could slow down solar poles to rotate slower than interior? Also – the whole southern solar hemisphere rotates faster than northern one during last decade. No, it is not a dynamo slowing the poles, it generates magnetic power from that slow-down instead, and it is not a perpetuum-mobile to generate power from it’s own consequences… It is also not a corriolis force of convection, very probably not…? Also, Sun is perfectly symmetric sphere and irregularity of it’s spin cannot be induced by gravity or tidal effects.)

    Gravity cannot influence rotation on a spherical body, only assymetries can have (tidal) effect. (Chandler wobble very probably caused by excess core mass below Pacific, which counter-balances excess surface mass on Africa, Andes and Himalayas missing in Pacific… Spinning body probably cannot spin on assymetrical axis for a long time(?), hence the counter-weight for that, what is missing on Pacific surface, should be on Pacific deep below… Otherwise calculating chandler wobble from gravitational influence of Sun,Moon and planets on assymetric surface mass distribution leads to similar but opposite direction effect than Chandler wobble and rotation axis shift. Which hinted me, that the core mass distribution (which should make Chandler wobble of rotational axis relative to body, which is something different than precession and nutation, which are wobble of rotational axis relative to outer space) should have opposite assymetry from surface mass distribution…)
    http://semi.gurroa.cz/Chandler/Chandler.html

    Moon is tidally locked with Earth, having the heavier half pointing outward… (Which somehow surprised me, I thought that the heavier half is that pointing toward Earth, but very probably it is not… Didn’t I confuse it?) It was also initially spining faster than orbiting and to brake that spin down, it had to transfer the angular momentum energy elsewhere – to planet Earth. By an assymetry of shape, since spherical body cannot transfer angular momentum.

  10. Keitho says:

    Well that was a very interesting, and provocative, article from which I have learned a lot of things I didn’t know. Thanks for putting it up Roger.

    Then I go to the comments and learn even more, and such surprising stuff too thanks especially to P.A. Semi for such information.

    Does anybody have any idea why the atmosphere is rotating so much faster than the planet, where does that energy come from? I am assuming it is the sun but by what mechanism?

    Every day I seem to discover more information that only seems to serve to show how little I know. Despite trying to add to what I know for the last seven decades I feel like I understand less and less.

    Thanks everybody for sharing your knowledge and insights.

  11. oldmanK says:

    @ P A Semi. T Y for the info. Much to digest, — with more than one lead.

    Just in case it might trigger a brain wave somewhere, recent info namely the Eddy cycle appeared to provide new leads to many questions on a particular subject of mine. That is periodic disasters in the holocene optimum as evident in archaeology. It was too much for simple coincidence. I have just added some and can be seen here: https://melitamegalithic.wordpress.com/?p=198

    On a hunch I had tried looking into ‘orbital resonances’ for a possible likely ‘controlling gremlin’. Earth Venus looked like a good candidate. As in my piece the Eddy cycle with a 53year spread (if I understood correctly) suggested an external forcing/trigger, but firing irregularly (geological disasters depend on several factors besides an external orbital catalyst).

  12. P.A.Semi says:

    About southern solar hemisphere rotating faster:
    My recent work on Solar surface flows (differential rotation, meridional flow, torsional oscilation)
    http://semi.gurroa.cz/Astro/Flow/FlowAvg.html#Cor

    Somewhere in middle of the page (search for “animation”) there are two AVI videos of solar surface magnetic field, best showing the differential rotation…

    On X-flow (zonal) chart it is visible, that southern part is red (faster) and northern blue (slower). There is also visible the torsional oscilation wave of slower and faster rotation, where the faster rotation (prograde wave) corresponds with sunspots.

    On Y-flow (meridional) chart it is visible slower-than-average poleward flow on north arround 2012 and faster-than-average poleward flow on south since 2017 (both visible as red spots, more southward/down than average), which I suspect of being planet-related, still pending to investigate this more…

    (It is not much related to Venus rotation talk of this blog-post, I’m just adding this, while I mentioned differences of Solar rotation above…)

  13. P.A.Semi says:

    Further thinking about Moon – it rather has lost it’s spin angular momentum transfering it to it’s own orbit angular momentum, not to Earth… Still, to transfer angular momentum, there must be some vehicle, like a mass irregularity in case of gravity- and inertia-assisted transfer…

    Further thinking about Venus and clouds – corriolis force makes most Earth clouds move from west to east (except near equator). On Venus, there should be opposite corriolis force, albeit much weaker than on Earth due to slower planet rotation. Then the polar vortexes on Venus could stir to spin all dense clouds from poles to equator? But how could solar radiation make the clouds to spin and thereby transfer radiation energy into angular momentum?

  14. oldbrew says:

    P.A.Semi says:
    July 24, 2018 at 4:19 pm (Edit)
    Further thinking about Moon

    Of course most regular-shaped moons of solar system planets have synchronous rotation i.e. 1 orbit of the planet = 1 rotation of that moon itself.

    Mercury’s spin is tied to its orbit period too – 3 spins = 2 orbits.

  15. P.A.Semi says:

    Regular-shaped moons, that have synchronous spin and orbit – are probably all somehow asymmetric, unless they are all molten, which they are probably not.
    For tidal force (tidal locking) to influence rotation, there must be some asymmetry, or mere friction of surface fluid over sea floor, which works much slower. (Otherwise tidal forces are symmetric on opposite sides, gravity and inertia are also symmetric on a symmetric body…)

  16. ferdberple says:

    Why does the drag between the surface and the atmosphere not cause the atmosphere to slow down. Why does it cause the much more massive planet to speed up. What dives the atmosphere to rotate faster than the much planet in spite of the drag.

  17. P.A.Semi says:

    Ferdberple – and why do you think the Venus atmosphere is not slowed down?
    It’s not slowed down to complete halt, though. Maybe it would spin even faster…

    Of cause, the conservation of energy must hold, and if planet’s spin is altered, something else must lose the angular momentum, which is the atmosphere.
    Energy is added to the system by solar radiation.

  18. oldbrew says:

    In just under 8 years (~2922 days) we get:
    12 Venus rotations = 2916.22 days
    13 Venus orbits = 2921.11 days
    25 Venus days = 2918.75 days
    5 Venus-Earth conjunctions = 2919.7 days
    115 solar rotations = 2918.7 days
    (last 3 of these are divisible by 5, first 2 sum to 5²=25)