1 00:00:00,000 --> 00:00:03,660 [ MUSIC ] 2 00:00:03,680 --> 00:00:13,820 The Lasting Impacts of Comet Shoemaker-Levy 9 – Presented by Science@NASA 3 00:00:13,840 --> 00:00:19,050 At the close of the last century, a comet, captured into orbit around a planet, 4 00:00:19,070 --> 00:00:28,600 traveled too close and was shredded by its gravity into multiple pieces, some as large as a half a mile (1 km) long. 5 00:00:28,620 --> 00:00:33,850 Those fragments would plunge into the the planet’s atmosphere in a series of impacts. 6 00:00:33,870 --> 00:00:40,150 Would the impacts be spectacular? Or would the comet fragments disappear without a trace? 7 00:00:40,170 --> 00:00:45,640 In July 1994, astronomers around the world watched with bated breath 8 00:00:45,660 --> 00:00:51,340 as the fragments of comet Shoemaker-Levy 9 slammed into the planet Jupiter. 9 00:00:51,360 --> 00:00:56,350 Dr. Kelly Fast was one of the impact’s observers, and is now manager of NASA’s 10 00:00:56,370 --> 00:00:59,300 Near-Earth Object Observations program. 11 00:00:59,320 --> 00:01:05,950 “It was just incredible to watch. Such an impact event had never before been witnessed, let alone studied. 12 00:01:05,970 --> 00:01:10,700 Ground-based telescopes around the world and spacecraft like NASA’s Hubble Space Telescope 13 00:01:10,720 --> 00:01:16,440 and even the Galileo orbiter en route to Jupiter were used to observe the impacts. 14 00:01:16,460 --> 00:01:24,340 The discovery of the comet by Carolyn and Gene Shoemaker and David Levy gave us about a year to plan our observations.” 15 00:01:24,360 --> 00:01:31,890 The impacts proved to be impressive: The fragments – some 21 in all – plunged into Jupiter’s atmosphere 16 00:01:31,910 --> 00:01:41,580 over the course of six days. At impact, they were traveling at a speed of about 37 miles/second (60 km/second), 17 00:01:41,600 --> 00:01:48,880 heating the atmosphere to at least 53,000 degrees Fahrenheit or 30,000 degrees Celsius. 18 00:01:48,900 --> 00:01:53,040 Like the splash from throwing a rock into a pond, 19 00:01:53,060 --> 00:01:57,180 the impacts created giant plumes of material from Jupiter’s lower atmosphere 20 00:01:57,200 --> 00:02:04,610 which rose as high as 1,900 miles or 3,000 kilometers above the cloudtops into the stratosphere. 21 00:02:04,630 --> 00:02:10,540 In the aftermath, the plume splashback scarred Jupiter’s atmosphere with dark clouds of impact debris 22 00:02:10,560 --> 00:02:16,620 which could be seen for months as they were gradually dispersed by Jupiter's winds. 23 00:02:16,640 --> 00:02:21,610 So what were scientists able to learn about Jupiter itself as a result of the impacts? 24 00:02:21,630 --> 00:02:28,470 For one thing, those dark clouds of impact debris acted as tracers of the winds in Jupiter’s stratosphere, 25 00:02:28,490 --> 00:02:34,890 and by following their motion over time, scientists could measure those high-altitude winds. 26 00:02:34,910 --> 00:02:43,180 Temporary changes in the aurora on Jupiter showed scientists that Jupiter’s magnetosphere was influenced by particles from the impacts. 27 00:02:43,200 --> 00:02:48,970 "We are still able to see changes in Jupiter’s atmosphere that resulted from the impacts. 28 00:02:48,990 --> 00:02:55,630 When the fragments of Shoemaker-Levy 9 slammed into Jupiter, they deposited their own chemical compounds, 29 00:02:55,650 --> 00:03:01,140 the impact processes produced some, and others were exhumed from the lower atmosphere. 30 00:03:01,160 --> 00:03:06,640 Some molecules, like ammonia, were destroyed by sunlight in the weeks and months after the impacts, 31 00:03:06,660 --> 00:03:12,220 but others, like hydrogen cyanide and water, are still seen today. 32 00:03:12,240 --> 00:03:16,750 All of that tells scientists about how chemistry works in Jupiter’s atmosphere." 33 00:03:16,770 --> 00:03:22,980 Comet Shoemaker-Levy 9 showed us that large impacts still happen in the Solar System, 34 00:03:23,000 --> 00:03:28,650 and were a factor in NASA developing programs to address the impact risk to Earth. 35 00:03:28,670 --> 00:03:32,680 From comet science, to Jupiter science, to the science of impacts, 36 00:03:32,700 --> 00:03:38,440 the legacy of that serendipitous discovery by Carolyn and Gene Shoemaker and David Levy 37 00:03:38,460 --> 00:03:42,780 continues to this day and into the future. 38 00:03:42,800 --> 00:03:59,380 For more impactful stories about comets and asteroids, visit science.nasa.gov.