The Crash Of Shoemaker-levy 9

August 27, 1994|By Lucy McFadden. and Lucy McFadden was one of the coordinators of worldwide viewing activities of the Shoemaker-Levy 9 crash into Jupiter. She is a visiting planetary scientist at the University of Maryland, College Park.

The spectacle of comet Shoemaker-Levy 9 pummeling Jupiter was a major news event last month (July 17-22). Scientists could scarcely contain their excitement as they described this unprecedented event to an eager world. But in the excitement of the moment, they failed to convey some very important points.

Now that the smoke has cleared somewhat, the real scientific work begins. The results of the work will help us better understand the birth and evolution of planets and the weather patterns of Jupiter. While seemingly of little direct benefit to us, this knowledge may ultimately prove invaluable.

NASA is mandated to explore the solar system. Since 1958, a generation of scientists has been doing just that. The most basic question driving the investigations is, How did the solar systm form?

This question has been asked since Copernicus convinced the world that the planets orbit the sun and rotate on their own axes, and that the dimensions of the solar system are small compared to the distances to the stars and the rest of the universe.

From the Apollo lunar missions we learned that the craters that dot the surface of the moon were formed by countless impacts over billions of years. The major sources of small projectiles are asteroids, residing in a swarm between Mars and Jupiter, and comets, remnants from the early solar system formation.

The significant role of comets and asteroids in the accretion of planets and the evolution of atmospheres has been hypothesized since the Apollo missions. Scientists and the public have now had the opportunity to directly observe this predicted process of planet formation.

We recorded the event and in the next few months we will be calibrating our data. We will present the initial findings in early November.

Those findings must be viewed in the context of the laws of physics. If our scientific observations don't agree with our predictions, then we are not understanding the physics involved and we must modify our model.

Why? So what if we don't understand the atmospheric circulation (weather) on Jupiter? So what if we don't understand how energetic particles emitted from the sun interact with the upper atmosphere of Jupiter and create electrical storms? How does that affect us?

It doesn't directly, but eventually it will. The laws of physics that drive the atmosphere of Jupiter and generate electrical storms and aurora are the same as those controlling the weather on Earth. By knowing how these systems function on other planets, we can apply our knowledge of the physical processes to predict phenomena that do matter to us on our planet.

Predicting a powerful atmospheric storm can save lives and minimize financial loss from property damage. Predicting an electromagnetic storm and taking proper precautions can maintain the telecommunications systems on which our civilization has come to depend.

Scientists face a mandate to direct their research toward areas that will improve the quality of life for us here on Earth. Exploration and study of the solar system provides a method of testing the scientific validity of models of Earth systems that are vital not only to our survival but to maintaining a habitable planet.

And finally, there is the matter of perspective.

Comet collisions can help us appreciate a number of celestial concepts. For example, recent studies have looked at the magnitude of the hazard to Earth from projectiles causing severe regional or climatic damage. Witnessing the collision of Shoemaker-Levy 9 with Jupiter brought home to us the reality of such a hazard.

Those of us who saw Jupiter were in awe that the face of the largest planet in the solar system changed before our very eyes. Yet while the energy of the comet impacts was impressive (estimated at 100 million megatons), it was paltry in terms of the entire universe. The sun puts out 3,800 times the energy of the collisions every second. And the energy of a supernova explosion is 20 orders of magnitude greater than the collisions.

I am continually humbled by the scale of the universe, and hope that people who took an interest in the collision of Shoemaker-Levy 9 with Jupiter last month also felt humbled.