(materials: corrected quizzes, "Venus Unveiled," containers and thermometer)
Questions on Reading
Quiz
1. Describe two early (pre-space-age) observations of Mars that encouraged people
to think that it might have vegetation, and even intelligent beings.
There seemed to be linear features that were mistakenly thought to be canals.
There were seasonal changes that might be due to vegetation. (actually were caused by wind blowing dust)
(Moral: Once again, scientists are like everyone else; we tend to see what we want to see and what we expect to see.)
2. List four modern observations of Mars which seem to indicate
that life there is very unlikely.
atmospheric pressure is too low to support liquid water on the
surface
very cold
no ozone layer means that UV light from Sun can reach the surface,
breaking molecules apart
atmosphere has no unusual gasses that might indicate life (eg.,
large amount of oxygen for the Earth)
3. Give two pieces of evidence that suggest that Mars once had liquid water on its surface.
features that look very much like dried up river beds
quantities of some atoms in the atmosphere (such as deuterium)
indicate that atmosphere was once dense enough to support liquid
water on the surface
4. List four difficulties that astronauts on Mars would encounter if they tried to boil an egg.
no wood for fire
no oxygen in atmosphere to allow wood to burn if you could find
the wood
very little water available
water in pot would sublime (go directly to a gas), unless you
used a pressure cooker
Why is Mars so unlike Earth?
...again, it's a case of location, location, location
...but, in the case of Mars, the other important factor is...
...the size of the planet. Since Mars is small, its gravity is...
...weak, which means that it can't hold onto its atmosphere as easily as Earth can. In addition, its small size led to its cooling much faster than Earth. (An everyday example of a small thing cooling faster than a big one is...
...a ferret, which is covered with hair to keep it warm, whereas a large animal, like a ...
...whale isn't. In fact, a whale would have a hard time surviving out of the water, which keeps it from overheating.)
Since it cooled much faster than Earth, there was less geological activity on Mars. Olympus Mons is so big because...
...Mars has had less geological activity than Earth and probably no plate tectonics, so all the material piled up in one place, unlike the Hawaiian Island chain. Also, there was less outgassing on Mars, which is partly responsible for the fact that it has a thinner atmosphere.
5. Describe a small, lightweight experiment that could have been carried aboard a Viking lander to attempt to detect microbial life on Mars. Be specific, referring to material from the reading. (“Creativity based on reality…”)
Practice Multiple-Choice Quiz
1. Mars differs from Earth in being...
A) smaller and hotter.
B) larger and more massive.
C) farther from the Sun and having a thinner atmosphere.
D) smaller, with a much higher surface gravity and much shorter rotation period.
Answer: C
2. One reason that scientists in the early 1900s thought that Mars might have life was that...
A) the Viking spacecraft sent back images showing patches that looked like moss.
B) there seemed to be canals.
C) large volcanoes were visible on the surface.
D) the atmosphere was made up mostly of oxygen.
Answer: B
3.Which of the following best describes the atmosphere of Mars as we understand it today?
A) mostly oxygen, and much colder than Earth's
B) mostly carbon dioxide, with significant quantities of water ice
C) mostly nitrogen, with a pressure much less than Earth's
D) mostly carbon dioxide, with a pressure much less than Earth's
Answer: D
4. Which of the following best describes the surface of Mars as we understand it today?
A) heavily cratered, with giant volcanoes
B) heavily cratered, with polar caps made of water ice
C) mountainous, with canals
D) covered with dried-up river beds, some of which are filled with water ice
Answer: A
5. Which of the following is the best evidence that life might be possible on Mars?
A) The length of a Martian day is similar to the length of an Earth day.
B) The noontime temperature reaches 20 degrees Celsius in places.
C) Liquid water can exist in places on Mars.
D) Seasonal changes in the appearance of Mars as seen from Earth indicate vegetation.
Answer: B (also C; many students made good arguments for this answer)
6. Which of the following is the best evidence that there may once have been liquid water on Mars?
A) The surface is a rust color.
B) The low deuterium-to-hydrogen ratio in the Martian atmosphere indicates that the atmosphere used to be much denser.
C) The high deuterium-to-hydrogen ratio in the Martian atmosphere indicates that the atmosphere used to be much denser.
D) The low deuterium-to-hydrogen ratio in the Martian atmosphere indicates that there used to be much less deuterium.
Answer: C
7. If Mars were moved closer to the Sun, which of the following would be the least likely to happen?
A) Ice currently in the form of permafrost would melt, releasing water vapor.
B) The orbital period of Mars would decrease.
C) The atmospheric pressure would increase.
D) The length of the Martian year would increase.
Answer: D
8. One problem that astronauts on Mars would not have if they tried to boil an egg is:
A) Matches wouldn't light.
B) If they tried to melt ice, it would never become liquid but would become vapor.
C) The egg would weigh so much that it would crack.
D) They'd have trouble finding fuel for the fire.
Answer: C
Conclusion of "Venus Unveiled"
Moral: People see what they want to see and what they expect to see.