I am interested in two aspects of this question. Imagine that Venus had a similar rotation speed and the same direction of rotation that we have here on Earth.

What would change for Venus itself? I'm interested about changes in the core and mantle behaviour, a potential magnetosphere, changes in the atmosphere and tectonic plates.

What would be different for the other planets near the Sun? I'm interested about changes in gravitational resonance and potential orbit changes.

  • $\begingroup$ Welcome on the site! Your question might be considered too broad or hyphothetical in its current form. Could you please make your question more detailed? For example, you could ask for the significant changes in the Venusian weather. $\endgroup$
    – peterh
    Jun 28, 2019 at 16:27
  • $\begingroup$ Thanks peterh! I did some changes on my question, still getting used to Stack dynamics. Im already loving this site!!! $\endgroup$
    – enochroot
    Jun 28, 2019 at 17:55
  • $\begingroup$ Are you asking if Venus had always had such a rotation or its current rotation were somehow slowed? $\endgroup$
    – BillDOe
    Jun 28, 2019 at 21:38
  • $\begingroup$ Im sorry, yes I'm asking about what if Venus had always such a rotation. How different would things be for Venus and its nearby planets than today. $\endgroup$
    – enochroot
    Jun 28, 2019 at 21:49

3 Answers 3


I'm interested about changes in the core and mantle behavior, a potential magnetosphere, changes in the atmosphere and tectonic plates.

A lot of this is very theoretical. Venus' atmosphere is nearly 100 times as massive Earth's atmosphere. It's also nearly all CO2, a greenhouse gas, which means it's good at trapping heat. That wouldn't change if Venus' rotation rate was faster.

"Core and mantle behavior" is a bit of an unusual statement, cores rotate with the planet and they slowly cool, there's some convection vs conduction going on, but it's difficult to study the cores of other planets. It's hard enough studying the core of Earth. But what we know of the core of Earth, or think we know is that Earth's core and Earth's crust rotate at slightly different rates. This may be due to Earth's crust slowing down over time and the core, not slowing down as fast. There's a slight variation in rotation rate. Also, Earth's inner core is solid, Earth's outer core is somewhat liquid (though extremely viscus), and as it cools, the inner core slowly grows, the outer core shrinks and in the process heat is released. This process creates a flow, which may be partially influenced by the Moons orbit, and together the circulations are thought to create Earth's magnetic field. This isn't certain, but the flow of the outer core is thought to be the cause and Earth's rotation may play a role in that.

So if Venus rotated much faster, in combination with it's proximity to the Sun and the solar tidal forces, it's possible a faster rotating Venus would have a permanent magnetic field. It's far from certain, but that's a possible outcome.

Plate tectonics is more tricky. Various studies suggest that planetary size has a lot to do with plate tectonics, and abundant water plays a role too, oceans making plate tectonics easier. Venus is on the small size and it has almost no water, so it's not a good candidate for plate tectonics. Venus also has very little granite. This is geology more than astronomy, but abundant granite (IMHO) plays a role in plate tectonics. The rocky bodies in our solar-system. Mercury, Venus, Mars, the Moon, are all, basically basalt like on their surfaces. Earth formed large granite land masses that float above the more dense basalt like layers under the oceans. Without granite land masses and without oceans, I don't think Venus is a good candidate for plate tectonics.

Did Venus ever have plate tectonics, like billions of years ago? Maybe. I have no idea, but maybe. Would it have plate tectonics if it rotated faster? I doubt it. A magnetic field - maybe. Plate tectonics, I don't think so.

This question is probably too general for stack exchange and it may be closed, but I don't believe that just spinning Venus faster would change all that much apart from maybe giving it a magnetic field, and that wouldn't change all that much on Venus. It has an induced magnetic field anyway.

If you could give Venus an ocean, maybe make it more massive and move it further away from the sun, then some interesting things might happen like plate tectonics, which could have lead the planet down a different path, perhaps more similar to Earth.

Earth was able to absorb CO2 into it's vast oceans and take in CO2 by photosynthesis and rocks were able to absorb CO2 by plate tectonics, and Earth was far enough from the sun to not have it's surface water evaporated and lost like what probably happened to Venus.

I think planetary formation, based on size, type of star, temperature, initial materials, etc, will be a very interesting field of study when/(if) big enough telescopes are set up to actually get a look at distant planets. It's very difficult to even observe, much less, study a planet that's light-years away. The so far twice or three ties delayed James Webb Space Telescope might get the ball rolling on this subject with better observations of exo-planet atmospheres, but it's a long ways away from being well understood. The James Webb ST is an enormously difficult undertaking, so we should be patient. With luck, it'll be up and taking in images within a few years.

Finally, would Venus' rotation, if it was faster, affect other planets? Basically not at all. Jupiter's rotation doesn't affect Earth. Rotation rate doesn't affect other objects at great distances.

  • $\begingroup$ If Venus were to have a magnetic field of any significance that could offer the atmosphere some protection against solar wind, it might have an even denser atmosphere, if that were possible, given the atmosphere is effectively a super critical fluid. $\endgroup$
    – Fred
    Dec 26, 2021 at 3:32

I believe a LOT would change. As someone who lives in the Northern hemisphere; we are closer to the sun during the winter months, but just a few more hours of daylight has a massive temp change. This change is 20-40 degrees colder compared to the summer months and we are over a million miles closer to the sun at this time.

If Venus had a moon of its own similar to Earth with possible impact origins. Its very thick atmosphere does collect greenhouse gasses but we don't understand the relation between the intense heat of 200+ Earth day long days has on its maintenance. It also would have an effect of reflecting sunlight and with a possible magnetic field; may even change the way the sun's radiation "radiates" for lack of better word, its atmosphere particles. Less ionization I presume. Venus could vary between almost habitable regions to 200+ degrees still, it is hard to tell which presuming it had near 24 hour days.

  • $\begingroup$ I've removed the supplemental question about Mars. The answer here seems to focus on a possible moon, rather than on the changes that short days would bring to Venus. As such I don't think it really answers the question very clearly. It would be better if the various claims were backed by evidence, rather than just being your presumptions. $\endgroup$
    – James K
    Dec 26, 2021 at 16:05

I don't think anything substantial would have changed. Four billion years ago, Venus was similar to Earth but hotter. It had seas, and like Earth, a very substantial atmosphere composed mainly of CO2. The rotation rate was probably not quite the same as it is today, but for your scenario let's suppose it was once every 24 hours. Owing to its greater proximity to the sun and the greenhouse effect of a CO2 atmosphere with a strong flavouring of methane, regardless of a 24 hour rotation rate the seas would have eventually evaporated away, increasing the greenhouse effect. Meanwhile, outgassing from volcanoes would have added more CO2 and sulphur dioxide to the toxic mix, forming sulphurous acid in combination with the water vapour. At a guess, I would think this took about a billion years, perhaps slightly faster than an earth-like rotation would have done. Venus's 8-month rotation rate would have meant that one side of the planet was exposed far longer to the sun's rays than was the case on Earth, so it also had very long nights.

The situation today is that despite the very long days and very long nights, the atmosphere is so thick that there is no significant difference in temperature between the night side of the planet and the day side. Had it been rotating every 24 hours, there might have been a temperature difference between night and day for the first few million years, but this would have decreased as the greenhouse atmosphere built up to become a more effective blanket. In other words, had Earth been 30 million miles closer to the sun, the same sort of thing would have happened here, so the answer to your question is that a more rapid rate of rotation wouldn't have made much difference.

  • $\begingroup$ Thanks Michael, I've realized that I always tend to forget about albedo! $\endgroup$
    – enochroot
    Jun 30, 2019 at 22:18

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