Our earliest atmosphere, formed by outgassing, was much poorer in ...

[evelyn o bentley]

Our earliest atmosphere, formed by outgassing, was much poorer in ________ than now.
 
  A) carbon dioxide
  B) hydrogen
  C) oxygen
  D) methane
  E) nitrogen

Question 2

Contrast open and globular star clusters.
 
  What will be an ideal response?

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Answer to Question 1

C

Answer to Question 2

Globular clusters are older (as old as the Galaxy, from 10-12 billion years old), contain many more stars (millions of stars for the richest ones), and are very poor in metals. Their brightest members have evolved into red giants, and their color magnitude diagram leaves the main sequence just above the Sun's position and curve into the giant branch to the top right. By contrast, most open clusters are much younger, with hot blue stars the brightest. They are made of a much larger fraction of heavy elements, produced by the many generations of supernovae that happened since the globular clusters formed.