Earth’s Origin and Early Evolution
1. Given a choice of the isotope systems discussed in this unit (Rb-Sr, Sm-Nd, U—Pb), which would you use to date an Archean metamorphic rock? Explain your rationale. (5 points)
2. When we say that a star is “burning” hydrogen, we mean something very different from what happens to hydrogen when it is burned on Earth. With reference to the equations below, explain how the process of “burning” in stars differs from the process of burning on Earth. Which process yields more energy? (5 points)
Burning of H in a star: 2H + 1H ‘He + y, where y is a gamma-ray
Burning of H on Earth: 2H2 + 02 =, 2H20 + heat For the remaining questions, refer to Table 1: Principal burning stages in hydrostatic stellar evolution, in Meteorites and the early solar system II by B. S. Meyer and E. Zinner (2006).
3. Figure 1.4 in Isotopes: Principles and Applications (Faure & Mensing, 2005, p. 12), shows the abundance of elements in the solar system (You can find Fig. 1.4 in the. Notice that the abundances of Li, Be, and B are very low compared to other elements plotted nearby. What does Table 1 (Meyer & Zinner, 2006) indicate might be the cause of these anomalous y ow abundances? (5 points)
4. The answer to Study Question 3 in Lesson 7 gives a much simpler account of stellar nucleosynthesis than does Table 1 (Meyer & Zinner, 2006), with fewer products. This is due, in part, to simplification for the purpose of this course. However, of these two accounts of nucleosynthesis, one description is more appropriate for a star existing early in the history of the universe, whereas the other description is best applied to a star existing today or in the recent past. Which description best applies to which star? Explain your reasoning. (5 points)
