Summary: Extraterrestrial Life: Problem Set #3
Due, in class, Thursday February 28th
1) Outline the key properties that seem to be common to all life on Earth.
Explain why the existence of these shared features supports the idea that
all life on Earth arose from a common ancestor.
2) Suppose that life is discovered on Mars. Explain how we might be able to
determine whether it shares a common ancestor with life on Earth. How
would the prospects for making such a determination be affected if all that
is found on Mars are fossils of life that died out hundreds of millions of
3) Suppose that (hypothetically, since I can't think how this could ever
happen) all life on Earth were suddenly to die out. Describe how the
atmosphere on the now-lifeless Earth would change. For how long would
evidence of past human civilization persist (i.e. if an alien civilization were
to visit the Earth thousands, millions, or hundreds of millions of years
later, how easily could they determine that an intelligent species had once
4) Describe what is meant by extremophiles. Why are extremophiles
considered to be important in guiding the search for extraterrestrial life.
5) Suppose that a small asteroid or comet like the one that struck an