A bad day on Venus gets even worse

February 29, 2012
Venus. Photo courtesy of NASA

Contrary to its alluring name, Venus is the planet from hell, with an atmosphere so hot, toxic and heavy that any visitor would risk being simultaneously melted, suffocated and crushed.

But not just that: the second planet from the Sun turns on its axis so slowly that, for any survivor, a Venusian day would seem interminable, for it is the equivalent of 243 days on Earth.

To make things worse, a day on Venus is getting even longer, French astronomers have discovered.

A team from the analysed data from a aboard a European orbiter, the Venus Express.

Called VIRTIS, the gadget measures infrared and and is used to scan the planet's surface beneath the thick, roiling atmosphere.

The astronomers were stunned when they checked landmarks against the last mapping of Venus, carried out between 1990 and 1994 by the US probe Magellan.

At a given point in the Venusian day, landmarks were a full 20 kilometers (12 miles) behind where they should have been.

The team, publishing in the journal Icarus, say they have been over the observations again and again.

"After eliminating possible sources of error, we believe that the duration of the Venusian day must have changed over the 16 years," they said in a press release.

Their calculation is that an extra six and a half terrestial minutes have been added to the Venusian day during this time.

"On the astronomical scale, this is a major change," said investigator Pierre Drossart.

The astronomers' is that friction by Venus' atmosphere is braking the movement of the terrain below.

That sounds bizarre until one realises that the atmosphere is 100 kms (60 miles) thick, with extremely of 96 percent , driven by superwinds reaching some 350 kilometres (210 miles) per hour.

at the surface is 92 times that of Earth -- the equivalent of being more than 900 metres (3,000 feet) below the ocean.

"A braking effect from the atmosphere also occurs erratically on Earth, but the discrepancy is only a matter of a few tenths of a second and it is imperceptible," Drossart told AFP.

So will Venus eventually stop spinning -- or even go into reverse rotation?

"It's difficult to say, given that we only have two points of measurement," said Drossart.

"But theoretical models suggest that this is probably just a cyclical phenomenon. If the atmosphere speeds up, the planet slows. Then the energy goes into reverse, in a pendulum effect."

Explore further: Europe's Venus Express is ready for launch

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5 / 5 (3) Feb 29, 2012
Whaaaaat? If this turns out to be true it's pretty crazy that the atmosphere of a terrestrial planet (even one that thick) can have that great an effect on the rotation of the planet.

I wonder what the momentum ratio of the atmosphere to the planet is? And how that compares to Earth's ratio?
5 / 5 (3) Feb 29, 2012
What's even more interesting is what did Venus look like a mere 100 million years ago if such a significant breaking is noted...what did it look like a billion years ago?
1 / 5 (1) Mar 01, 2012
A more direct measurement of its day length should be made instead of the extrapolation based on the offset of landmarks that they used. It shouldn't be all that hard to do, so I'm quite confused why it wasn't done or mentioned in the article.

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