Red spots are massive storm systems. The largest one (GRS) has been raging on the surface of Jupiter since telescopes first studied it some 350 years ago. It is the largest hurricane known in the solar system. The smaller storm that remains, Red Spot Jr., is roughly half the size of its famous counterpart, but has winds just as strong. It formed between 1998 and 2000 from the merger of three long-lived white ovals (smaller storms), and in February 2006 astronomers noticed that it had turned red.
Some astronomers think that the consumption of Baby Red shows how GRS has managed to survive for so long, through "stealing" the energy from the many smaller storms it has devoured over the centuries. Of course it is only recently that we have had powerful enough telescopes to see this PacMan behaviour in progress.
For more information about NASA's Hubble Space Telescope, click here.