Venus Express now tells us exactly how windy it is above Venus

Friday, September 19, 2008

This is really important information because the cloudtops of Venus are the most Earthlike environment in the Solar System, and could be colonized relatively easily. As a quick introduction, the cloudtops about 50 km above the surface of Venus have the following characteristics:

  • A temperature about that of the Earth
  • Air pressure the same as sea level
  • Mostly CO2 just like everywhere else, meaning that breathable air for humans rises like helium does here
The problem has always been the phenomenon of super-rotation, the high speeds you encounter in the winds up there. Estimates before have been about 100 m/s or 360 kph. Today ESA released more detailed information on exactly what the speeds are like at what level:
Observing at the infrared wavelength of 1.74 micrometres on the night-side of the planet, VIRTIS can see down to 45-47 km altitude; the clouds at this altitude can be seen because they absorb infrared light coming from the surface and the lower atmospheric layers, and this light is then re-emitted by the clouds themselves. At this height, the average wind speed is about 210 km/h.

Observing in the near-infrared (about 980 nanometres) and in the blue ultraviolet (about 350 nanometres) on the day-side of the planet, VIRTIS can look down to about 61 and 66 km altitude (the higher part of the cloud layer), respectively. Sunlight reflected by the clouds at the two different layers in the infrared and in the ultraviolet makes it possible to track them. The measured wind speeds are 220 and 370 km/h, respectively.
The wind speed really picks up somewhere in between 61 and 66 km, but by that height the average temperature is -10 to -30C and the air pressure about 10% that of Earth. Luckily the part where humans could most easily inhabit (about 52 km or so) is below the higher speeds.

There are some other aspects to the winds that has some information on, where this variance in wind speeds only happens away from the poles and wind speeds are higher in the evenings.

How does this compare to Earth? The jet stream on Earth is generally between 80 and 160 kph, and can reach up to 400 kph as well, so somewhat faster than that on average.

Considering that life could exist in the cloudtops of Venus, I say it's high time we send a solar flyer mission to the cloudtops to investigate them in greater detail:
But the planet's dense atmosphere is ideal for a flying craft. A wing's lift depends directly on the density of the atmosphere and the atmospheric pressure on Venus is about 90 times that of Earth. After being released by an orbiter, the craft's origami-like wings would unfurl from an "aeroshell" (see Graphic). Solar panels on the craft's surface could absorb large amounts of the intense solar energy, powering motors to allow the craft to fly continuously. And the planet's slow rotation, with one day and night on Venus taking 117 Earth days, means a solar flyer could stay on the daylight side indefinitely.


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