Monday, July 18, 2011

Seventeenth Anniversary for Jupiter's Impact by Comet

Through July 16 - 22 1994, Comet Shoemaker-Levy cruised into Jupiter's southern hemisphere, leaving a scar that can never be removed. Nicknamed "String of Peals" later on for its behavior during the crash, Jupiter survived and is still in orbit as of today! Below, we remember this 'fateful' day as we remind ourselves of the crash, which indeed did not only just hit Jupiter, but some of the Galilean moons as well.

Brown spots in the southern hemisphere indicate where Jupiter was impacted by this comet.

According to NASA, "This is the first collision of two solar system bodies ever to be observed, and the effects of the comet impacts on Jupiter's atmosphere have been simply spectacular and beyond expectations. Comet Shoemaker-Levy 9 consisted of at least 21 discernible fragments with diameters estimated at up to 2 kilometers" That's one reason why this comet was nicknamed "String of Peals." The comet broke up simultaneously leaving a repeated scar on the surface of Jupiter and a few moons.

This is the surface of Ganymede with the repetition pattern
Ganymede, shown above, was one of the objects beside Jupiter that was hit by Comet Shoemaker-Levy. You can notice the patterns of the comet breaking up, where the series of craters sit. The whole picture is about 120 miles across.

Crater chain on Callisto, another Galilean moon. This caption is by NASA:
This image taken by the Voyager spacecraft of an unnamed crater chain is one of the longest of 12 or so such chains on Callisto, one of Jupiter's 4 planet-sized satellites. It is 360 kilometers long and the largest individual crater is approximately 24 kilometers across. Photo credit: Paul Schenk/Lunar & Planetary Institute

During the Voyager missions to the planet, planetary scientists have identified impacts on Galilean moon Callisto, as well as Ganymede. Thirteen crater chains (called 'catena,' plural 'catenae') have been discovered on Callisto, while three on Ganymede. You can see, from the picture generated below by Sky&Telescope's Jovian moon applet, Callisto (C) and Ganymede (G) were in row with Jupiter as the comet hit. This is one reason why they were probably hit. Io (I) is in eclipse (you can't see it) and Europa (E) is out of the way.

More evidence points to this because the chart below of daily events of the Jovian moons shows Ganymede going into transit, which is going over the surface of Jupiter. It's more vulnerable to getting hit that way.

Monday, July 18, 1994
15:10 UT, Io enters occultation behind Jupiter.
18:40 UT, Io exits eclipse by Jupiter's shadow.
20:18 UT, Ganymede begins transit of Jupiter.
22:16 UT, Ganymede ends transit of Jupiter.

Another impact on Jupiter
As you go on with your day, remember Jupiter, and also know that this is common. NASA astronomers have found this to be quite common, although we don't notice it many a time. Come here for an extravaganza of images, video coverage, and much more multimedia of this 'tragic' event! NASA has done a great job of collecting it all. Goodbye for now, Jupiter.

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