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Chapter 15: Problem 45

For many years it was thought that the Tunguska event was caused by a comet striking the Earth. This idea was rejected because a small comet would have broken up too high in the atmosphere to cause significant damage on the ground. Explain why, using your knowledge of a comet's structure.

Short Answer

Expert verified
A comet comprises primarily of ice, dust, and rocks. As it enters Earth's atmosphere, the heat and friction caused by the atmosphere cause the ice to sublimate and the comet to break apart. This effect would be significant in a smaller comet, resulting in its disintegration high in the atmosphere, thus preventing any major ground damage.

Step by step solution

01

Understanding a Comet's Composition

Comets are celestial bodies that orbit the sun, just like planets. They are composed primarily of ice, dust, and rocky material. The icy portion consists of water, carbon dioxide, ammonia, and other frozen gases. When the comet approaches the sun, the ice begins to vaporize and create a 'coma' - a bright, hazy cloud around the comet's nucleus.
02

The Role of Earth's Atmosphere

Earth's atmosphere acts as a protective shield against many celestial objects. As these objects enter the atmosphere, they face significant frictional force which results in intense heat. This intense heat is capable of disintegrating small objects before they reach the ground.
03

Why the Comet Breaks Up in the Atmosphere

Given a comet's composition being primarily fragile and volatile materials, it would start to disintegrate under the intense heat generated by the friction with Earth's atmosphere. Because the majority of a comet is made up of ices, the high thermal energy leads to rapid sublimation of this ice into gaseous form. Consequently, a small comet would not maintain its integrity and would break apart high in the atmosphere, before it could cause any significant damage on the ground.

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Most popular questions from this chapter

Sun-grazing comets come so close to the Sun that their perihelion distances are essentially zero. Find the orbital periods of Sun-grazing comets whose aphelion distances are (a) 100 \(\mathrm{AU}\), (b) \(1000 \mathrm{AU}\), (c) \(10,000 \mathrm{AU}\), and (d) \(100,000 \mathrm{AU}\). Assuming that these comets can survive only a hundred perihelion passages, calculate their lifetimes. (Hint: Remember that the semimajor axis of an orbit is one-half the length of the orbit's long axis.)

Why are asteroids, meteorites, and comets all of special interest to astronomers who want to understand the early history and subsequent evolution of the solar system?

What is the evidence that carbonaceous chondrites are essentially unaltered relics of the early solar system? What do they suggest about how the solar system may have formed?

Describe the asteroid belt. Does it lie completely within the plane of the ecliptic? What are its inner and outer radii?

A very crude model of a typical comet nucleus is a cube of ice (density \(1000 \mathrm{~kg} / \mathrm{m}^{3}\) ) \(10 \mathrm{~km}\) on a side. (a) What is the mass of this nucleus? (b) Suppose \(1 \%\) of the mass of the nucleus evaporates away to form the comet's tail. Suppose further that the tail is 100 million \(\left(10^{8}\right) \mathrm{km}\) long and 1 million \(\left(10^{6}\right) \mathrm{km}\) wide. Estimate the average density of the tail (in \(\mathrm{kg} / \mathrm{m}^{3}\) ). For comparison, the density of the air you breathe is about \(1.2 \mathrm{~kg} / \mathrm{m}^{3}\). (c) In 1910 the Earth actually passed through the tail of Comet Halley. At the time there was some concern among the general public that this could have deleterious effects on human health. Was this concern justified? Why or why not?
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