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Chapter 15: Problem 47

From the abundance of craters on the Moon and Mercury, we know that numerous asteroids and meteoroids struck the inner planets early in the history of our solar system. Is it reasonable to suppose that numerous comets also pelted the planets \(3.5\) to \(4.5\) billion years ago? Speculate about the effects of such a cometary bombardment, especially with regard to the evolution of the primordial atmospheres on the terrestrial planets.

Short Answer

Expert verified
Yes, given the chaotic nature of the early solar system and the composition of comets being made up of ice and organic molecules, it is reasonable to suggest that comets could have also bombarded the inner planets. Such a bombardment could have contributed to the formation of oceans and atmospheric gases such as water vapor, carbon dioxide, and ammonia, hence playing a significant role in the evolution of the primordial atmospheres on the terrestrial planets.

Step by step solution

01

Understanding the historical context

Firstly, it is necessary to understand that the early solar system was a chaotic place with numerous bodies colliding. The high number of craters on the Moon and Mercury provide evidence that inner planets were bombarded by meteoroids and asteroids. This period is often referred to as the Late Heavy Bombardment.
02

Analysing the composition of comets

Comets are composed mainly of ice, complex organic molecules, dust and rocks. They originated from the outer regions of the solar system, so it is plausible that comets also hit the inner planets during the early periods of the solar system.
03

Astromical Consequences of Cometary Bombardment

The collision of comets with terrestrial planets could lead to the formation of oceans and atmospheric gases. If comets bombarded the inner planets, the ice in comets could have melted and become a part of the planets' water supply. This is one popular theory about the origin of Earth's water.
04

The contribution to planetary atmospheres

In addition to water, comets carry complex organic molecules. Upon impact, these molecules could escape and accumulate forming the early atmospheres of the planets. This might have influenced the development of primordial atmospheres on inner planets, and perhaps the beginning of life on Earth, though these are all speculative explanations.

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Most popular questions from this chapter

What are Kirkwood gaps? What causes them?

Why do comets have prominent tails for only a short time during each orbit?

Use the Starry Night Enthusiast ?M program to study the motion of a comet. First set up the field of view so that you are observing the inner solar system from a distance (select Solar System > Inner Solar system in the Favourites menu). In the toolbar, click on the Stop button to halt the animation, and then set the date to January 1,1995 , and the time step to 1 day. Select View \(>\) Solar System \(>\) Asteroids in the menu to remove the asteroids from the view. Open the Find pane and center on Comet Hyakutake by typing "Hyakutake" in the Search All Databases box and then pressing the Enter key. Use the Zoom controls to decrease the field of view to about \(25^{\circ} \times\) \(17^{\circ}\). Then click on the Run Time Forward button. (a) Watch the motion of Comet Hyakutake for at least two years of simulated time. Describe what you see. Is the comet's orbit in about the same plane as the orbits of the inner planets, or is it steeply inclined to that plane? (You can tilt the plane of the solar system by holding down the Shift key while clicking on and moving the mouse to investigate this off-ecliptic motion.) How does the comet's speed vary as it moves along its orbit? During which part of the orbit is the tail visible? In what direction does the tail point? (b) Click on the Stop button to halt the animation, and set up the field of view so that you are observing from the center of a transparent Earth by selecting Guides \(>\) Atlas in the Favourites menu. Set the date to January 1, 1995, and the Time Flow Rate to 1 day, and again center on Comet Hyakutake. Use the controls at the righthand end of the toolbar to zoom out as far as possible. Then click on the Run Time Forward button and watch the comet's motion for at least two years of simulated time. Describe the motion, and explain why it is more complicated than the motion you observed in part (a). (c) Stop the animation, set the date to today's date, set the Time Flow Rate to 1 month ("lunar m."), and restart the animation. Comet Hyakutake is currently moving almost directly away from the Sun and so, as seen from the Sun, its position on the celestial sphere should not change. Is this what you see in Stamy Night Enthusiast \(\mathrm{\text {??? }}\) Explain any differences. (Hint: You are observing from the Earth, not the Sun.)

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?

How do modern astronomers discover new asteroids?
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