Jupiter, spot by spot

Contributed by
Jul 23, 2006

A while back I wrote that a new storm on Jupiter would pass by the Great Red Spot, and while they weren't expected to interact very much, it should make for an interesting sight.

Well, I called it right on the money.

The encounter between the two spots was captured by the giant Gemini telescopes in July. The image is in the infrared (in visible light both spots would be red). The astronomers used three filters (ranging from just outside what our eyes can detect in IR to way out in the IR spectrum) just like they would for an optical image. The filters used really bring out the spots, so they are very easy to see. Here's what the astronomers say about the images:

In this color composite image, white indicates cloud features at relatively high altitudes; blue indicates lower cloud structures; and red represents still deeper cloud features. The two red spots appear more white than red, because their tops hover high above the surrounding clouds.

Given that one of the filters they used sees the "thermal" infrared (meaning it detects warm gas, something like room temperature or so) I suspected at first that the colors represented temperatures. However, it's not that simple, since at least one filter they used detects hydrogen (that's blue in the image), and another detects methane (green in that image). So red stuff is warm (deeper in the atmosphere the temperature increases, so red=deep), but blue is hydrogen (which must be more prevalent lower down but not as low as the red stuff) and green is methane. All three colors together make white, so the tops of the clouds must be warm, and have lots of hydrogen and methane. The warmth is interesting, as you might expect cloud tops to be cool; but it's possible that a warm upwelling of gas in Jupiter is making the smaller spot rise in altitude. That would explain why it's warm, and has hydrogen and methane, too.

All in all, planetary atmospherics is a tough discipline, and I for one am glad we have so many experts studying it. By analyzing systems like Jupiter, we can understand our own weather better. It's been 95 - 100+ degrees here every day where I live, so I'd be pretty happy if people understood exactly why. Maybe someday we will.

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