The storm clouds can be seen both on infrared images as on the forms of Hubble Space Telescope. (c) ESA-NASA / GCP-UPV / EHU
Read aloud Tumultuous states dominated the atmosphere of the giant planet Jupiter more than a year ago. On March 25, two more than one hundred kilometers of storm clouds piled up at the 23rd northern latitude, report researchers Agustin Sanchez-Lavega in the journal Nature. The development of the storms gave the researchers the unique opportunity to learn about the conditions under the dense cloud cover of Jupiter. The Hubble Space Telescope had been monitoring Jupiter more closely since February 2007, as a flyby of the Pluto probe was approaching New Horizons, which also included scientific data. As a result, the two storms were discovered unusually fast. Jupiter's atmosphere consists of white and reddish cloud bands that run along the latitudes. The bands remain stable for decades. In the high atmosphere, above the visible cloud cover, strong winds develop analogous to the jet stream on earth. The causes of both phenomena are still unclear.

As Sanchez-Lavega and his colleagues write, the storms occurred in the cloud band with the strongest jet stream. The speed is between 140 and 180 meters per second. "We were able to observe how the diameter of cloud fungi grew within one day from 400 to 2000 kilometers, " says Sanchez Lavega. The researchers found that the storm clouds projected 30 kilometers beyond the tropopause of Jupiter. The tropopause is actually the upper boundary layer for all weather phenomena, both on Earth and Jupiter. It also forms the upper limit of the visible clouds. The storms must therefore have been extremely energy-rich, the researchers write.

The two storms originated more than 60, 000 kilometers apart and had their origins both in the layer of water clouds enveloping the planet. The storms carried a mixture of ammonia ice and water into the high Jupiter atmosphere. In the shadow of the two storms, the cloud band was vigorously mixed, which made it a reddish hue. In the following weeks, Jupiter's turbulence was also observed in other cloud bands.

The researchers calculated that the temperature in the source region of the storms must have been two to five degrees lower than during earlier measurements. Since the jet stream could not be distracted by the storms, the researchers assume that this strong wind zone extends to a hundred kilometers below the visible cloud cover. This in turn provides information about the propulsion of the jet stream: While on the Earth caused by the sun temperature differences for the strong wind, the Jupiter winds reach into zones where the sunlight can not go. "There's every indication that Jupiter's jets have a deep root, " says Sanchez-Lavega, "so there's probably a source of heat inside Jupiter that drives the jets." Ad

Jupiter radiates more heat into space than it absorbs from the sun. Where the extra heat comes from has long been a mystery to planetary scientists. However, the new observations could at least help clarify the peculiarities of heat transport in the giant gas planet. The turbulence on Jupiter also seems to follow a fairly regular pulse: in 1975 and 1990, similar changes in the atmosphere were observed.

Agustin Sanchez-Lavega (Basque University) et al .: Nature Vol. 451, p. 437, 409 Ute Kehse

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