Questions for ‘Will we know alien life when we see it?’


The aliens that humankind encounters will probably be small and hardy, not huge, city-killing monsters like those seen in the movies.


To accompany feature “Will we known alien life when we see it?


Before Reading

1.  If you were informed that NASA had just confirmed the presence of life beyond Earth, what would you imagine that newfound life to look like?

2.  If future astronauts encountered a “being” on some distant planet that acted like a robot but not quite, how could they determine if it was “alive” or not?

During Reading:

1.  What are astrobiologists?

2.  What are three requirements — criteria — that some scientists have suggested would be necessary to distinguish alien microbes?

3.  What are ribosomes? 

4.  Why do many scientists argue that viruses are not alive? What is Christoph Adami’s argument for refuting that assessment?

5.  Why did Kathie Thomas-Keprta and her team think they had found life on a Martian meteorite in 1996? How did other scientists shoot down that claim?

6.  What is desert “varnish” and why does Carol Cleland make the case it could be a marker of life?

7.  How many minerals have been found on Earth, and what share of them exist in only one or two places?

8.  Name two moons on which liquid oceans exist covered by icy crusts.

9.  Name three reasons life would likely grow — or age — slowly on Titan, if it existed there at all.

After Reading

1.  Science fiction stories have for more than a century asked us to envision an encounter with extraterrestrials? Why? What is the appeal of contemplating life beyond Earth — and especially encounters between humans and extraterrestrials?

2.  Imagine a race — or perhaps many — of colonial microbes. Could they be “intelligent?” Explain your reasoning.


1.  Of the 4,831 minerals that Robert Hazen and his colleagues have mapped, 22 percent exist in only one location. How many minerals would that be? (Show your work.)

2.  Human adults breathe an average of 14 times per minute. How many breaths would that equal over the course of a year? Now, if a tiny alien on Titan took that same number of breaths over its entire lifetime — but only at a rate of one breath every 100 years, how long in Earth years would it live? Show your work.