New insights on Venus’ cloud-tops and super-rotation 

Posted: September 29, 2019 by oldbrew in atmosphere, research, satellites, wind
Tags: , ,

Venus


The article here notes that: ‘The atmosphere of Venus – which is mostly carbon dioxide – is extremely dense and hot; atmospheric pressure on Venus’ surface is some 90 times that of Earth.’ An extremely dense atmosphere with enormous atmospheric pressure is always going to be hot, regardless of its composition. Just a thought, but maybe it needs a lot of convection (wind) to offset the heat.

Why does Venus’ upper atmosphere circle the planet in just 4 Earth-days, while the planet itself takes 243 Earth-days to spin once?

Japan’s Akatsuki spacecraft probed the mysterious “super-rotation” of Venus’ clouds, reports EarthSky.org.

The spacecraft – aka the Venus Climate Orbiter – got off a rocky start but has been sending back useful data from Venus for several years now.

Akatsuki launched in May, 2010, but failed to enter orbit around Venus in December of that year. Space engineers saved the day with a 20-minute firing of the craft’s attitude control thrusters, placing the craft into an alternative orbit around Venus – albeit a highly elliptical one – five years later, in 2015.

This month, at the EPSC-DPS Joint Meeting 2019 in Geneva, Switzerland, Kiichi Fukuya of the University of Tokyo reported on new insights into the mysterious super-rotation of Venus’ atmosphere, made possible by Akatsuki’s data.

That is, the upper atmosphere of Venus rotates around the planet much faster than the planet spins; the atmosphere rotates around the planet in just 4 Earth-days, while the planet itself takes 243 Earth-days to spin once. Fukuuya said:

The most exciting discovery is the frequent occurrence of equator-ward motions [of the atmosphere] on the nightside. This is in contrast to the strong poleward circulation on the dayside we have observed previously at other wavelengths.

Overall, these scientists reported that data from Akatsuki show:

… striking variety in wind speeds year-on-year and between the planet’s northern and southern hemispheres.

Takeshi Horinouchi of Hokkaido University, Japan, and Yeon Joo Lee of JAXA/ISAS and TU Berlin also detected planetary-scale atmospheric waves at the cloud tops, which may interact with the super-rotation. For these studies they used:

… advanced cloud-tracking and quality control techniques to analyze with high accuracy the direction and speed of cloud top winds using data collected by [Akatsuki’s] Ultraviolet Imager instrument over three years.

And they said the difference they observed in Venus winds between the planet’s hemispheres might be linked to a second mystery at Venus: an as-yet unidentified chemical in the atmosphere that strongly absorbs ultraviolet radiation from the sun.

You might know that Venus is considered Earth’s “twin” in size and density. It’s a world very similar to Earth in many ways, but its atmosphere sets it apart. The atmosphere of Venus – which is mostly carbon dioxide – is extremely dense and hot; atmospheric pressure on Venus’ surface is some 90 times that of Earth.

This as-yet-unknown ultraviolet absorber in the atmosphere is interesting to these scientists because its variability in Venus’ atmosphere might cause the asymmetry in wind speeds between the planet’s northern and southern hemispheres.

Full report here.

Comments
  1. Curious George says:

    The atmosphere of the young Earth was probably mostly CO2. Over time, it was converted to fossil fuels and carbonate rocks, mostly by biological processes. Venus seems to be very similar to the Earth, indeed.

  2. oldbrew says:

    Earth is a 3-cell per hemisphere system but Venus is said to have a ‘planet-wide Hadley cell’.

    https://en.wikipedia.org/wiki/Atmosphere_of_Venus#Circulation

    ESA animation…

    Earth’s Hadley cells…

  3. p.g.sharrow says:

    Venus is not a twin of Earth, It never was. Venus and Earth have much different origins and development.
    At present they occupy similar orbits and are of similar size, that is all they have in common.
    With a dry atmosphere that is 90 times more dense then Earth, Venus is a good, what if, study on how an atmosphere might behave, IF, the planet had very little rotation and a very dense atmosphere. Mean while on Earth, we barely understand how this atmosphere works after studying it close up for thousands of years…pg

  4. gallopingcamel says:

    p.g. said”
    “Mean while on Earth, we barely understand how this atmosphere works after studying it close up for thousands of years…pg”

    “Barely understand” is way too strong since we can’t explain the various warm periods that have occurred over the past 5,000 years.

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