Giant gravity wave is spotted on Venus: Bow-shaped feature stretches 6,200 miles across its atmosphere 17 January 2017
Venus is covered in a thick atmosphere, with clouds of sulphuric acid moving westwards faster than the planet itself rotates.
But among this fast-moving atmosphere scientists have discovered a mysterious ‘sideways smile’ on its surface stretching 6,200 miles (10,000 km) across.
The stationary patch could be a giant wave caused by the gravity from mountains below, the first of its kind to be observed on the planet, according to a new study published today.

The mysterious patch was captured by JAXA’s Akatsuki spacecraft, as a bright spot in images.
Researchers from the Rikkyo University in Tokyo studied the bow-shaped patch, after it was spotted in December 2015.
‘The bow is a pair of high and low temperature regions, of which amplitude is about 5km, extending from the northern high latitudes across the equator to the southern high latitudes with an end-to-end length of 10,000 km or longer,’ lead author Makoto Taguchi told MailOnline.
The stationary bow of temperatures lasted between 7 and 11 December.

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Interesting result from a mission that was nearly lost

> Researchers from the Rikkyo University in Tokyo studied the bow-shaped patch, after it was spotted in December 2015.

Ah yes, I remember seeing that at the time. I was totally mystified. Because it bore no resemblance to the V-shaped cloud patterns seen in UV.

> The stationary patch could be a giant wave caused by the gravity from mountains below, the first of its kind to be observed on the planet, according to a new study published today.

Nice. Yes, that makes sense.

‘The bow is a pair of high and low temperature regions, of which amplitude is about 5km, extending from the northern high latitudes across the equator to the southern high latitudes with an end-to-end length of 10,000 km or longer,’ lead author Makoto Taguchi told MailOnline.

The stationary bow of temperatures lasted between 7 and 11 December.

‘The most surprising feature of the bow is that it stayed at almost same geographical position despite the background atmospheric super-rotation, the uniform westward wind of which the maximum speed is 100 metres/second at the cloud-top altitudes,’ Taguchi said.

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Facinating

Could this really be due to gravity? Isn’t deflection of the wind by mountain slopes more likely?

Don’t we have a map of the surface elevation of Venus?

> Could this really be due to gravity? Isn’t deflection of the wind by mountain slopes more likely?

Same thing. The deflection by mountain slopes provides the impetus that generates the wave. Then subsequent development is due to gravity in a stably stratified atmosphere, like the familiar waves that develop at the surface between two immiscible liquids, or even more familiarly mountain lee waves.

> Don’t we have a map of the surface elevation of Venus?

From the Magellan radar map, yes. I assume that the authors have matched the wave location to some mountains on the surface underneath.

mollwollfumble said:

> Could this really be due to gravity? Isn’t deflection of the wind by mountain slopes more likely?

Same thing. The deflection by mountain slopes provides the impetus that generates the wave. Then subsequent development is due to gravity in a stably stratified atmosphere, like the familiar waves that develop at the surface between two immiscible liquids, or even more familiarly mountain lee waves.

OK, I thought they meant variations in the gravity field due to the mountains.

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.

A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a wave orbit. Gravity waves on an air–sea interface of the ocean are called surface gravity waves or surface waves, while gravity waves that are within the body of the water (such as between parts of different densities) are called internal waves. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides.

Wind-generated gravity waves on the free surface of the Earth’s ponds, lakes, seas and oceans have a period of between 0.3 and 30 seconds (3 Hz to 0.03 Hz). Shorter waves are also affected by surface tension and are called gravity–capillary waves and (if hardly influenced by gravity) capillary waves. Alternatively, so-called infragravity waves, which are due to subharmonic nonlinear wave interaction with the wind waves, have periods longer than the accompanying wind-generated waves.

wiki

ChrispenEvan said:

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.

A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a wave orbit. Gravity waves on an air–sea interface of the ocean are called surface gravity waves or surface waves, while gravity waves that are within the body of the water (such as between parts of different densities) are called internal waves. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides.

Wind-generated gravity waves on the free surface of the Earth’s ponds, lakes, seas and oceans have a period of between 0.3 and 30 seconds (3 Hz to 0.03 Hz). Shorter waves are also affected by surface tension and are called gravity–capillary waves and (if hardly influenced by gravity) capillary waves. Alternatively, so-called infragravity waves, which are due to subharmonic nonlinear wave interaction with the wind waves, have periods longer than the accompanying wind-generated waves.

wiki

Thanks CE. I wasn’t familiar with these being called gravity waves. Perhaps I’m just out of touch (at least with fluid dynamicists).

The Rev Dodgson said:

Thanks CE. I wasn’t familiar with these being called gravity waves. Perhaps I’m just out of touch (at least with fluid dynamicists).

I am familiar with it, but even I have to check each time to be sure I’m saying “gravity wave” not “gravitational wave” in stratified fluid, and “gravitational wave” not “gravity wave” in general relativity.