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A third giant red storm has flared up on Jupiter, joining the Great Red Spot and the recently developed Red Spot Junior. The spot, along with new measurements of record-high wind speeds on Red Spot Junior, come at a time when the solar system鈥檚 largest planet is experiencing a time of global upheaval.

Jupiter鈥檚 Great Red Spot is an ancient, hurricane-like storm that may have been raging for 340 years or more, based on early observations with telescopes. At three times the width of Earth, it is the largest storm in the solar system.

It was recently joined by a similar, but smaller storm called Red Spot Junior. Red Spot Junior grew out of the merger of three smaller, white storms between 1998 and 2000 and turned red in 2006. It is about the size of Earth.

Now, a third red spot, about half the size of Red Spot Junior, has broken out on the giant gaseous planet. The spot, previously a white storm, now appears red in Hubble Space Telescope images taken on 9 and 10 May. The observations were led by Imke de Pater of the University of California, Berkeley, US.

No one knows for sure what gives the three spots their red colour. But one theory is that especially violent storms dredge up material from deeper in Jupiter鈥檚 atmosphere, such as phosphorus-containing molecules, which undergo chemical reactions that turn them red when exposed to sunlight.

Ferocious winds

The cloud band containing the Great Red Spot has been especially stirred up, changing 鈥渇rom a rather bland, quiescent band surrounding the Great Red Spot just over a year ago to one that is incredibly turbulent at both sides of the spot鈥�, de Pater told New 杏吧原创.

New measurements also suggest that Red Spot Junior鈥檚 winds are increasing in ferocity. A team led by Andrew Cheng of the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Maryland, US, made the wind measurements by tracking cloud features in images taken 30 minutes apart by the New Horizons spacecraft as it whizzed by Jupiter in February 2007 on its way to Pluto.

The results suggest that Red Spot Junior鈥檚 winds are now tearing around at nearly 620 kilometres per hour 鈥� matching the strongest winds ever observed in the Great Red Spot, and much faster than the winds in the largest of the three white storms that merged to make Red Spot Junior.

Destabilising force

鈥淢aybe it鈥檚 the increasing violence of the storm that enables it to become red, but that鈥檚 somewhat speculative,鈥� team member Hal Weaver of APL told New 杏吧原创.

But Philip Marcus of UC Berkeley, a member of de Pater鈥檚 team, says he doubts that the winds have increased so much. Based on Hubble images taken in 2006, he calculates that Red Spot Junior鈥檚 winds were moving at just 360 kilometres per hour.

Marcus thinks such a big change in wind speed between his observations in 2006 and the New Horizons flyby in 2007 is unlikely. 鈥淚鈥檓 sceptical, but open minded,鈥� he told New 杏吧原创.

The new observations come at a time of global upheaval on Jupiter that has dramatically changed the planet鈥檚 appearance.

The upheaval may be connected to a decades-long cycle proposed Marcus, a member of de Pater鈥檚 team. According to this theory, varying wind patterns periodically destabilise Jupiter鈥檚 atmosphere, leading to major changes on the planet.