# Why does Venus have retrograde rotation? **URL:** \ **Category:** Factual Questions\ **Created:** [April 13, 2021, 9:24pm UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930 "2021-04-13T21:24:45Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [April 13, 2021, 9:24pm UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/1 "2021-04-13T21:24:45Z")
Are there any theories to explain its retrograde rotation? ---
**Author:** ![TheGunIsMightierThanThePen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/thegunismightierthanthepen/32/2981_2.png) [@TheGunIsMightierThanThePen](https://boards.straightdope.com/u/TheGunIsMightierThanThePen)\ **Post date:** [April 13, 2021, 9:36pm UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/2 "2021-04-13T21:36:04Z")
> **[Retrograde and prograde motion | Planets](https://en.wikipedia.org/wiki/Retrograde_and_prograde_motion#Planets)** > > All eight planets in the Solar System orbit the Sun in the direction of the Sun's rotation, which is counterclockwise when viewed from above the Sun's north pole. Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus. Venus's axial tilt is 177°, which means it is rotating almost exactly in the opposite direction to its orbit. Uranus has an axial tilt of 97.77°, so its axis of rotation is approximately p... > [@](#): > > It is unlikely that Venus was formed with its present slow retrograde rotation, which takes 243 days. Venus probably began with a fast prograde rotation with a period of several hours much like most of the planets in the Solar System. Venus is close enough to the Sun to experience significant gravitational [tidal dissipation](https://en.wikipedia.org/wiki/Tidal_locking), and also has a thick enough [atmosphere](https://en.wikipedia.org/wiki/Atmosphere_of_Venus) to create thermally driven atmospheric [tides](https://en.wikipedia.org/wiki/Tide) that create a retrograde [torque](https://en.wikipedia.org/wiki/Torque). Venus’ present slow retrograde rotation is in [equilibrium](https://en.wikipedia.org/wiki/Mechanical_equilibrium) balance between gravitational tides trying to [tidally lock](https://en.wikipedia.org/wiki/Tidal_locking) Venus to the Sun and atmospheric tides trying to spin Venus in a retrograde direction. In addition to maintaining this present day equilibrium, tides are also sufficient to account for evolution of Venus’s rotation from a primordial fast prograde direction to its present-day slow retrograde rotation. ---
**Author:** ![penultima\_thule](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/penultima_thule/32/3833_2.png) [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)\ **Post date:** [April 13, 2021, 10:52pm UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/3 "2021-04-13T22:52:58Z")
Some things are unfathomable: [![](https://i.ibb.co/C5Gkcgm/Mars-Venus.jpg) ](https://i.ibb.co/C5Gkcgm/Mars-Venus.jpg) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 13, 2021, 10:57pm UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/4 "2021-04-13T22:57:10Z")
Surprisingly, Earth also seems to play a part in the tidal effects on Venus: Whenever the two planets are at closest approach, Venus is always showing the same face to us. ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [April 14, 2021, 12:26am UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/5 "2021-04-14T00:26:29Z")
How can they tell? All we see is clouds. (I believe you, really asking) ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [April 14, 2021, 12:32am UTC](https://boards.straightdope.com/t/why-does-venus-have-retrograde-rotation/939930/6 "2021-04-14T00:32:20Z")
There have been some orbiters of Venus. For example, the [Pioneer Venus Orbiter](https://en.wikipedia.org/wiki/Pioneer_Venus_OrbiterPioneer%20Venus%20Orbiter) had cloud-penetrating radar: > [@](#): > > - a **surface radar mapper (ORAD)** to determine topography and surface characteristics. Observations could only be conducted when the probe was closer than 4700 km over the planet. A 20 watt [S-band](https://en.wikipedia.org/wiki/S-band) signal (1.757 [gigahertz](https://en.wikipedia.org/wiki/Gigahertz)) was sent to the surface that reflected it, with the probe analyzing the echo. Resolution at [periapsis](https://en.wikipedia.org/wiki/Periapsis) was 23 x 7 km. It orbited Venus for 14 years.