Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Textbook Question
Chapter 8, Problem 45IF
Miniature Mars. Suppose Mars were significantly smaller than its current size—say, the size of our Moon. How would this have affected its potential habitability? Explain.
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Students have asked these similar questions
How is a habitable zone likely to change over time?
a. get narrower
b. move further from the star
c. they aren't likely to change
Which of the following is least reasonable regarding the concept of a habitable zone?
Group of answer choices
M-type stars have wider habitable zones than G-type stars.
It is a region around a star where liquid water could be found on a planet's surface.
The habitable zone of a less massive star would be closer to the star.
In the course of millions of years, our habitable zone will slowly shift from Earth to Mars.
The Galactic habitable zone cannot be too close to the Galactic center because the radiation from the bright stars and supernovae in the crowded inner part of the Galaxy would probably be detrimental to life.
Tutorial
A radio broadcast left Earth in 1923. How far in light
years has it traveled?
If there is, on average, 1 star system per 400 cubic light
years, how many star systems has this broadcast
reached?
Assume that the fraction of these star systems that
have planets is 0.50 and that, in a given planetary
system, the average number of planets that have
orbited in the habitable zone for 4 billion years is 0.40.
How many possible planets with life could have heard
this signal?
Part 1 of 3
To figure out how many light years a signal has
traveled we need to know how long since the signal left
Earth. If the signal left in 1923, distance in light years =
time since broadcast left Earth.
d = tnow - broadcast
d = 97
97 light years
Part 2 of 3
Since the radio signal travels in all directions, it
expanded as a sphere with a radius equal to the
distance it has traveled so far. To determine the
number of star systems this signal has reached, we
need to determine the volume of that sphere.
V, =
Vb…
Chapter 8 Solutions
Life in the Universe (4th Edition)
Ch. 8 - Briefly summarize the evidence, both real and...Ch. 8 - What would it be like to walk on Mars today?...Ch. 8 - Why isnt liquid water stable at the martian...Ch. 8 - How do martian seasons differ from Earth seasons?...Ch. 8 - Give a brief overview of the geography and major...Ch. 8 - How do we know that different regions of the...Ch. 8 - Summarize the evidence suggesting that Mars must...Ch. 8 - What evidence suggests that water might still flow...Ch. 8 - Why do we conclude that Mars must once have had a...Ch. 8 - What is the leading hypothesis concerning how Mars...
Ch. 8 - How and why does Marss axis tilt change with time,...Ch. 8 - Based on all the geographic and geological...Ch. 8 - Briefly summarize the Viking experiments and their...Ch. 8 - What is the potential significance of atmospheric...Ch. 8 - Briefly summarize plans for Mars exploration over...Ch. 8 - Discuss the issue of biological contamination in...Ch. 8 - Summarize the scientific pros and cons of sending...Ch. 8 - What do we mean by terraforming Mars? Is it...Ch. 8 - How do we know that ALH84001 really came from...Ch. 8 - Briefly summarize the possible evidence of past...Ch. 8 - The first human explorers on Mars discover that...Ch. 8 - We discover a string of active volcanoes in the...Ch. 8 - We find underground pools of water on the slopes...Ch. 8 - We discover that Mars was subjected to global,...Ch. 8 - A future orbiter finds a plume of volcanic gas...Ch. 8 - We find a lake of liquid water filling a small...Ch. 8 - The first fossils discovered on Mars come from the...Ch. 8 - A sample return mission finds fossil evidence not...Ch. 8 - We discover that the martian polar caps have in...Ch. 8 - We find rocks on Mars showing clearly that the...Ch. 8 - When we say that liquid water is unstable on Mars,...Ch. 8 - Marss seasonal winds are driven primarily by (a)...Ch. 8 - Olympus Mons is (a) a giant volcano; (b) a huge...Ch. 8 - We can recognize the oldest surface regions of...Ch. 8 - Minerals in surface rock studied by the martian...Ch. 8 - Rivers on Mars (a) have never existed; (b) existed...Ch. 8 - Which must be true if Mars was warmer and wetter...Ch. 8 - Which of the following fundamental properties of...Ch. 8 - According to the leading hypothesis, if Mars once...Ch. 8 - The Viking experiments found (a) no evidence of...Ch. 8 - The Role of the Martians. Percival Lowell may have...Ch. 8 - Learning from Past Mistakes. The Viking missions...Ch. 8 - Hold Your Breath. If you held your breath, would...Ch. 8 - Miniature Mars. Suppose Mars were significantly...Ch. 8 - Larger Mars. Suppose Mars were significantly...Ch. 8 - Civilization on Mars. Based on what we can see on...Ch. 8 - Martian Fossil Hunting. On Earth, we cannot find...Ch. 8 - Future Landing Site. Suppose you were in charge of...Ch. 8 - Terraforming Mars. Make a list of the pros and...Ch. 8 - Mars Movie Review. Watch one of the many science...Ch. 8 - Interior Heat. Compare the surface areatovolume...Ch. 8 - Atmospheric Mass of Earth. What is the total mass...Ch. 8 - Atmospheric Mass of Mars. The weaker gravity of...Ch. 8 - Past Gas on Mars. Models suggest that Mars today...Ch. 8 - Lessons from Mars. Discuss the nature of the...Ch. 8 - Human Exploration of Mars. Should we send humans...Ch. 8 - Current Mars Missions. Pick one of the Mars...Ch. 8 - Future Mars Missions. Pick one of the Mars...
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- Tutorial A radio broadcast left Earth in 1925. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.30 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.85. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1925, distance in light years = time since broadcast left Earth. d = tnow - tbroadcast d = light years Submit Skip (you cannot come back)arrow_forward25. When Mars is 90 million km from Earth, a) How long would it take for a radio wave from a video camera mounted on the back of a Mars Rover to tell ground control on earth that the Rover is about to go over a cliff? b) How long would it take for a radio signal from Earth to reach the Rover saying "STOP". c) Why do our Mars Rovers have to be "intelligent" enough to figure out how to deal with obstacles themselves?arrow_forwardWhat is the best way to determine if a exoplanet has life inside it? Group of answer choices Detect the star the exoplanet is orbiting and compare it to the Sun. Detect the exoplanet and determine if it is in the habitable zone of the star. Detect the exoplanet and study the atmosphere of the exoplanet. Detect the exoplanet and determine its age to see if it is similar to the age of the Earth.arrow_forward
- For which of the following reasons (select all that apply), is it useful/important to send rovers to other planetary bodies in our solar system? O a. The engineering innovations developed to produce successful/viable rovers and landers on other planets can help lead to developments in the technology used here on Earth that may have taken far more time to develop without the limitations provided by space travel to foreign worlds. O b. The data collected can help improve our understanding of the evolution/development of our solar system. O. Rovers/landers can be outfitted with various tools and equipment that can be used to inform of us of the geological histories of each of the planets they visit. O d. More direct probes of the planetary surface are possible to detect signs of the building blocks of life. O e. Rock samples can be used to calibrate our estimations of the age of the solar system.arrow_forwardActivity #1. Compare and Contrast. Similarities and differences of Venus, Earth and Mars. Do this on a separate sheet of paper. 1. Compare and contrast the three (3) terrestrial planets using table 1. 2. Provide explanations for your observations using table 2. 3. Answer the following guide questions. Guide questions: 1. Does planet size affect gravity? 2. Why do you think Venus has the highest mean temperature among the three planets? 3. Is presence of water a primary factor for a planet to sustain life? Why or why not? 4. Based on your observations using table 2, what are the notable features that makes the earth the only habitable planet among the three terrestrial planets? 5. What conclusions can you make?arrow_forwardWhat is a habitable zone?arrow_forward
- How can a planet’s atmosphere affect the width of the habitable zone in its planetary system?arrow_forwardWhat are the three requirements that scientists believe an environment needs to supply life with in order to be considered habitable?arrow_forwardIn this chapter, we identify these characteristic properties of life: life extracts energy from its environment, and has a means of encoding and replicating information in order to make faithful copies of itself. Does this definition fully capture what we think of as “life”? How might our definition be biased by our terrestrial environment?arrow_forward
- If we do find life on Mars, what might be some ways to check whether it formed separately from Earth life, or whether exchanges of material between the two planets meant that the two forms of life have a common origin?arrow_forwardIf you represent Earth’s history by a line 1 m long, how long a segment would represent the 400 million years since life moved onto the land? How long a segment would represent the 4-million-year history of human life?arrow_forward7. Complete the table below for the habitability of several solar system planets. Temperature can be hot, moderate, or cold. Amount of atmosphere can be thin, thick, or moderate. Liquid wa- ter amount can be lots, little, or none. Planet Venus Temperature Liquid Water Atmosphere Earth Marsarrow_forward
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