麻豆传媒

Images showing holes in Venus鈥檚 cloud deck and a mysterious wave pattern were released on Thursday in honour of the one-year launch anniversary of Europe鈥檚 Venus Express spacecraft.

Venus Express was launched on 9 November 2005 and entered orbit around Venus on 11 April 2006 to study the planet鈥檚 atmosphere. It is trying to find out what causes the winds that tear around the planet at up to 360 kilometres per hour and whether there is any current volcanic activity on the planet.

One of the newly released images shows a mysterious wave pattern in the atmosphere. It consists of regularly spaced clouds with gaps in between them. In this image, the clouds are dark because they are silhouetted against the infrared glow coming from deeper in Venus鈥檚 atmosphere. The gaps between them are bright because they let more infrared light through.

Mission scientists do not yet know what causes this pattern. It appears at mid-latitudes between the equator and the south pole, but not elsewhere, says team member Pierre Drossart of the Observatoire de Paris-Meudon in France.

Rising gas

It might be generated where the planet-circling winds have different speeds on either side of a 鈥榖order zone鈥�, or it might be related to gas rising and falling in the atmosphere, he says.

The pattern bears some resemblance to another wave pattern called the 鈥渟tring of pearls鈥� seen by the Cassini spacecraft in the clouds of Saturn (see Bizarre 鈥榮tring of pearls鈥� adorns Saturn).

But the two are not necessarily related, Drossart says. 鈥淒ifferent waves can look very similar even if they are very different in nature,鈥� he told 麻豆传媒.

Another image taken of the region near the south pole shows a large bright patch. This is an area where a thinning in the clouds allows infrared light to shine through from below 鈥� the planet鈥檚 surface is a sweltering 450掳 Celsius.

Such areas of thin clouds 鈥渕ake it possible to probe very deep in the atmosphere鈥�, says team member Giuseppe Piccioni of the Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) in Rome, Italy.

Both images were taken in infrared light using the spacecraft鈥檚 Visible and Infrared Thermal Imaging Spectrometer (VIRTIS).