Close encounter for Jupiter spots

The two spots appear white in this infrared image (Image: Gemini Observatory)

Jupiter's two giant red spots have brushed past each other, after approaching on a "collision course".

The Great Red Spot has been known for at least 130 years. The newer spot, nicknamed "Red Jr", formed from three smaller features between 1998 and 2000.

The two spots are actually massive storm systems in Jupiter's atmosphere.

A head-on collision was never on the cards; the spots which merged to form Red Jr have passed by the Great Red Spot many times, without incident.

The atmospheric current in which they were embedded moves at a different speed from the one at the latitude of the Great Red Spot.

Over time, the two spots change relative positions causing periodic close passages like this one. But this is the first such passage since the new, smaller red spot intensified and turned red.

A picture of the event has been captured by the Gemini North telescope in Hawaii by astronomers Travis Rector and Chad Trujillo.

No one is quite sure why the spots are red.

One theory is that the storm dredges material from deep beneath Jupiter's cloudtops and lifts it to high altitudes. Here, ultraviolet rays from the Sun might turn colour-changing compounds (or chromophores) red.