Ultraviolet Images Reveal Jupiter's Upper Atmospheric Winds
These four NASA Hubble Space Telescope images of Jupiter, as seen in visible (violet) and far-ultraviolet (UV) wavelengths, show the remarkable spreading of the clouds of smoke and dust thrown into the atmosphere after the impacts of the fragments of comet P/Shoemaker-Levy 9. These dark regions provide the only information ever obtained on the wind direction and speed in Jupiter's upper atmosphere.
TOP Three impact sites appear as dark smudges lined up along Jupiter's southern hemisphere (from left to right, sites C, A, and E). This pair of images was obtained on 17 July, several hours after the E impact. These 3 impact sites appear strikingly darker in the far-ultraviolet images to the right. This is because the smoke and dust rising from the fireballs absorbs UV light more strongly than violet light, so that the clouds appear both darker and larger in the UV images. Apparently, the fireball and plume threw large amounts of material completely above the atmosphere. This material diffused back down through the atmosphere with the smaller and lighter particles suspended at high altitudes.
BOTTOM Hubble's view of the same hemisphere of Jupiter 12-13 days later shows that the smoke and dust have now been spread mainly in the east/west direction by the prevailing winds at the altitude where the dark material is suspended or "floating" in the atmosphere.
HST shows that winds in Jupiter's upper atmosphere carry the high altitude smoke and dust in different directions than in the lower atmosphere. For example, the UV image shows a fainter cloud near 45 deg. south latitude, which does not appear in the violet image. The fainter cloud may be due to high altitude material which is drifting with the upper atmospheric winds to the north away from the polar regions. However, in the left-hand impact regions the clouds being observed are lower in the atmosphere where there is apparently no such northerly wind.
The violet images show the Great Red Spot, on the eastern (right) limb, one of Jupiter's moons crossing in front of the planet in the northern hemisphere (and its shadow on Jupiter's clouds on the left-hand side in the lower image), and the dark clouds above 3 of the impact sites near 45 deg. south latitude. In addition, Jupiter's polar aurora can also be seen in the far-ultraviolet images near both northern and southern poles.
The images were taken with the Wide Field Planetary Camera 2.
Credit: J.T. Clarke, G.E. Ballester (University of Michigan), and J.T. Trauger (Jet Propulsion Laboratory), and NASA