Question

section 1–2
analyzing data
write answers on
separate page.
the scientific method
a. read the passage and answer the questions that follow.
on july 20, 1976, the viking i lander touched down on the dusty red surface of mars. a few
months later, the viking ii lander arrived on another martian plain. the primary mission of
these two robot spacecraft was to determine if there was life on mars.
conditions on mars were thought to be far too harsh for large life forms. there is no liquid
water on mars and the atmosphere is very thin. during the course of a day, the temperature on
mars may range from 10°c to −80°c. the large changes in temperature produce strong winds
and planetwide dust storms. because of these conditions, scientists decided to look for
microorganisms rather than large life forms.
the viking spacecraft performed several experiments. in one experiment, samples of soil
were taken from different locations. the soil samples were put into a nutrient broth that
supported the growth of microorganisms on earth. the amount of carbon dioxide in the broths
was tested over a period of time.
scientists were excited to discover that martian soil produced carbon dioxide in the nutrient
broth. however, the amount of carbon dioxide produced in the martian soil was much smaller
than the amount that would be produced by living things on earth. thus, the results of the
viking spacecraft experiments are not conclusive. scientists are still not sure if life exists on
mars.

1. what assumptions did scientists make in this experiment?

1. why did scientists obtain soil samples from different places and from different parts of the

martian soil?

1. which characteristic of life was being tested for in the experiment?

1. why can’t scientists be sure if life exists on mars?

Explanation:

1. Scientists assumed Martian microorganisms (if present) would grow in the nutrient broth and produce CO₂ like Earth's microorganisms.
2. To increase the likelihood of detecting life by sampling diverse locations where life might exist.
3. The characteristic tested was metabolism (production of CO₂ as a byproduct of life processes).
4. Because the amount of CO₂ produced by Martian soil was much smaller than that from Earth's living things, making results inconclusive.

Answer:

1. Scientists assumed Martian microorganisms (if present) would grow in the nutrient broth and produce CO₂ like Earth's microorganisms.
2. To increase the likelihood of detecting life by sampling diverse locations where life might exist.
3. Metabolism (production of CO₂ as a byproduct of life processes).
4. The amount of CO₂ produced by Martian soil was much smaller than that from Earth's living things, so results are inconclusive.