Question 1

What is the Allen Telescope Array?

Accepted Answer

A) a large radio telescope array in Texas, which will concentrate on watching for signals from a single nearby star over time 
B) a large radio telescope array designed to work in tandem with the Kepler spacecraft, which is observing nearby stars for planetary systems 
C) a large radio telescope array that will concentrate on 100,000 nearby solar-type stars 
D) a series of a dozen radio telescopes placed in orbit where they are more effective at receiving radio signals 
A) a large radio telescope array in Texas, which will concentrate on watching for signals from a single nearby star over time 
B) a large radio telescope array designed to work in tandem with the Kepler spacecraft, which is observing nearby stars for planetary systems 
C) a large radio telescope array that will concentrate on 100,000 nearby solar-type stars 
D) a series of a dozen radio telescopes placed in orbit where they are more effective at receiving radio signals C

Question 2

Organic compounds have been found in each of the following EXCEPT ONE. Which is the EXCEPTION?

Accepted Answer

A) meteorites 
B) comet spectra 
C) interplanetary dust 
D) spectra of asteroids 
A) meteorites 
B) comet spectra 
C) interplanetary dust 
D) spectra of asteroids D

Question 3

Why do we believe that some meteorites, such as the Antarctic find ALH 84001, originated on Mars?

Accepted Answer

A) The color matched the red of the Martian soil. 
B) Each of these meteorites landed in soft soil or snow in such a manner that the landing trajectory could be determined. 
C) The ALH 84001 meteorite was actually tracked by radar on the final part of its inbound journey. 
D) The air trapped in pockets in the meteorites matched the Martian atmosphere but was very different from Earth's atmosphere. 
A) The color matched the red of the Martian soil. 
B) Each of these meteorites landed in soft soil or snow in such a manner that the landing trajectory could be determined. 
C) The ALH 84001 meteorite was actually tracked by radar on the final part of its inbound journey. 
D) The air trapped in pockets in the meteorites matched the Martian atmosphere but was very different from Earth's atmosphere. D

Question 4

If we were able to detect radio signals from an intelligent civilization, we would hope they are doing all of the following things, EXCEPT ONE. What is the EXCEPTION?

Accepted Answer

A) sweeping the skies with a focused beam of radio waves 
B) using a broadband of radiation to target more receivers 
C) using a frequency near the "water hole" 
D) using a repeating signal unlike a natural source like a pulsar 
A) sweeping the skies with a focused beam of radio waves 
B) using a broadband of radiation to target more receivers 
C) using a frequency near the "water hole" 
D) using a repeating signal unlike a natural source like a pulsar

Question 5

A key target in our radio telescope search for exoplanets harboring life is:

Accepted Answer

A) ozone because it is produced from oxygen and easy to detect in the infrared part of the spectrum. 
B) silicon because it is one of the most abundant elements on Earth and also a possible candidate as a base for biological molecules. 
C) carbon because our life-forms are based on carbon. 
D) iron because advanced civilizations are hard to imagine without it. 
A) ozone because it is produced from oxygen and easy to detect in the infrared part of the spectrum. 
B) silicon because it is one of the most abundant elements on Earth and also a possible candidate as a base for biological molecules. 
C) carbon because our life-forms are based on carbon. 
D) iron because advanced civilizations are hard to imagine without it.

Question 6

Why do we only consider stars with masses less than about 1.5 Me in the Drake equation when estimating the number of possible stars in our galaxy around which planets could form that would support our kind of intelligent life?

Accepted Answer

A) This type of star would produce so much damaging UV radiation that it would sterilize its planets. 
B) Such massive stars would never reach temperatures sufficient to maintain life-supporting conditions on the surfaces of its planets. 
C) Stars more massive than this would have evolved so rapidly that a sufficiently advanced civilization would not have had time to evolve and develop. 
D) Planets could not form sufficiently close to such stars for life to have survived and evolved. 
A) This type of star would produce so much damaging UV radiation that it would sterilize its planets. 
B) Such massive stars would never reach temperatures sufficient to maintain life-supporting conditions on the surfaces of its planets. 
C) Stars more massive than this would have evolved so rapidly that a sufficiently advanced civilization would not have had time to evolve and develop. 
D) Planets could not form sufficiently close to such stars for life to have survived and evolved.

Question 7

In a few decades, orbiting telescopes such as Kepler and James Webb Space Telescope (JWST) may be operational and sending us data. What might these results mean for our use of the Drake equation?

Accepted Answer

A) mirrors whose shapes are precisely determined by laser-computer mechanisms 
B) active optics 
C) adaptive optics 
D) interferometry 
A) mirrors whose shapes are precisely determined by laser-computer mechanisms 
B) active optics 
C) adaptive optics 
D) interferometry

Question 8

What are amino acids?

Accepted Answer

A) the simplest living organisms 
B) substances found in Earth's atmosphere, and perhaps on other bodies as well, which attack simple life-forms 
C) carbon compounds considered key to life because they are found only in very primitive life-forms 
D) the building blocks of proteins, the foundation of Earth-based life 
A) the simplest living organisms 
B) substances found in Earth's atmosphere, and perhaps on other bodies as well, which attack simple life-forms 
C) carbon compounds considered key to life because they are found only in very primitive life-forms 
D) the building blocks of proteins, the foundation of Earth-based life

Question 9

Which molecules, whose absorption lines appear in the infrared, are considered most likely to indicate the presence of life if they were detected on any planet orbiting another star?

Accepted Answer

A) hydrogen and helium 
B) methane and ammonia 
C) carbon dioxide 
D) carbon dioxide, ozone, and water vapor 
A) hydrogen and helium 
B) methane and ammonia 
C) carbon dioxide 
D) carbon dioxide, ozone, and water vapor

Question 10

Some meteorites found on Earth are believed to come from Mars because trapped bits of atmosphere in these meteorites match the composition of Mars's atmosphere. What more can be said about this?

Accepted Answer

A) The comparison to Mars's atmosphere is to recent samples taken by the Viking Landers. However, this is not a problem because Mars's atmosphere has been stable for a long time. 
B) The atmospheric samples in the meteorites contained much water vapor, further evidence of a wet period in Mars's past. 
C) The atmospheric samples in the meteorites are very different from the samples gathered by the Viking Landers of the present composition of Mars's atmosphere. But the meteorites are believed to contain samples of an ancient Martian atmosphere. 
D) Some of the meteoritic rocks have also been traced to specific craters on Mars. 
A) The comparison to Mars's atmosphere is to recent samples taken by the Viking Landers. However, this is not a problem because Mars's atmosphere has been stable for a long time. 
B) The atmospheric samples in the meteorites contained much water vapor, further evidence of a wet period in Mars's past. 
C) The atmospheric samples in the meteorites are very different from the samples gathered by the Viking Landers of the present composition of Mars's atmosphere. But the meteorites are believed to contain samples of an ancient Martian atmosphere. 
D) Some of the meteoritic rocks have also been traced to specific craters on Mars.

Question 11

Since the wobble that we have used to detect Jupiter-sized planets around other stars would be extremely small for an Earth-sized planet, we plan to use several other techniques to find and analyze Earth-sized planets in the near future. These include all but one of the following. Which one is the EXCEPTION?

Accepted Answer

A) transits 
B) detection of infrared radiation 
C) searching for objects with high albedos, indicating the presence of water or ice 
D) analysis of atmospheric spectra 
A) transits 
B) detection of infrared radiation 
C) searching for objects with high albedos, indicating the presence of water or ice 
D) analysis of atmospheric spectra

Question 12

In which of the following environments have long-chain carbon-based molecules not been found?

Accepted Answer

A) in interstellar gas clouds 
B) on the surface of Earth 
C) inside meteorites 
D) on the surfaces of nearby planets such as Venus and Mars 
A) in interstellar gas clouds 
B) on the surface of Earth 
C) inside meteorites 
D) on the surfaces of nearby planets such as Venus and Mars

Question 13

In what way was volcanism important to the development of life on Earth?

Accepted Answer

A) Volcanoes provided the heat necessary for the chemical reactions to create complex organic molecules. 
B) Amino acids were probably present in the gases emitted. 
C) Carbon dioxide, water vapor, and nitrogen were outgassed from volcanoes. 
D) Molten lava dissolved various organic materials on Earth's surface and allowed them to mix together so they could react. 
A) Volcanoes provided the heat necessary for the chemical reactions to create complex organic molecules. 
B) Amino acids were probably present in the gases emitted. 
C) Carbon dioxide, water vapor, and nitrogen were outgassed from volcanoes. 
D) Molten lava dissolved various organic materials on Earth's surface and allowed them to mix together so they could react.

Question 14

We believe the meteorite ALH 84001 came from Mars because of trace amounts of gas trapped in the rock. What does analysis of this gas reveal?

Accepted Answer

A) The gas matches the carbon dioxide-nitrogen composition of Mars's very early atmosphere some 4.5 billion years ago. This is also the age given by radioactive dating of this meteorite. 
B) The gas contains a combination of water vapor, iron oxide, and carbon dioxide, which we believe are unique to the surface of Mars in its "wet" period 4.5 billion years ago. 
C) The gas matched the current composition of the Martian atmosphere measured by the Viking Landers. This would also be the composition when the rock was blasted off the surface 16 million years ago. Presumably, this blast would have melted the rock and trapped some gas inside. 
D) In addition to a composition that matches the atmosphere of Mars, the gas contains the right amount of space dust to be consistent with orbiting the Sun for 16 million years. 
A) The gas matches the carbon dioxide-nitrogen composition of Mars's very early atmosphere some 4.5 billion years ago. This is also the age given by radioactive dating of this meteorite. 
B) The gas contains a combination of water vapor, iron oxide, and carbon dioxide, which we believe are unique to the surface of Mars in its "wet" period 4.5 billion years ago. 
C) The gas matched the current composition of the Martian atmosphere measured by the Viking Landers. This would also be the composition when the rock was blasted off the surface 16 million years ago. Presumably, this blast would have melted the rock and trapped some gas inside. 
D) In addition to a composition that matches the atmosphere of Mars, the gas contains the right amount of space dust to be consistent with orbiting the Sun for 16 million years.

Question 15

Several lines of evidence now suggest that large and complex organic molecules, from which the building blocks of life could be formed, have evolved in outer space. Which of the following is NOT one of these observational findings?

Accepted Answer

A) the discovery of large organic molecules on and under the soils of Mars and the Moon 
B) laboratory experiments in which electrical sparks passing through a combination of simple gases such as H2O, H2, N2, and CO2 produced large organic molecules 
C) radio astronomical observations of large organic molecules in giant molecular clouds 
D) the discovery of organic molecules inside certain meteorites that arrived upon Earth 
A) the discovery of large organic molecules on and under the soils of Mars and the Moon 
B) laboratory experiments in which electrical sparks passing through a combination of simple gases such as H2O, H2, N2, and CO2 produced large organic molecules 
C) radio astronomical observations of large organic molecules in giant molecular clouds 
D) the discovery of organic molecules inside certain meteorites that arrived upon Earth

Question 16

The method used in the Urey-Miller experiment was to:

Accepted Answer

A) pass an electric arc through a mixture of hydrogen, ammonia, methane, and water and then look for organic compounds. 
B) send radio signals using a pulsed code toward nearby Sun-like stars that may have planets. 
C) attach a metal plaque to the Voyager spacecraft to tell extraterrestrial beings about us, if they ever find the spacecraft. 
D) monitor tens of millions of frequencies at once in an effort to detect extraterrestrial radio communications. 
A) pass an electric arc through a mixture of hydrogen, ammonia, methane, and water and then look for organic compounds. 
B) send radio signals using a pulsed code toward nearby Sun-like stars that may have planets. 
C) attach a metal plaque to the Voyager spacecraft to tell extraterrestrial beings about us, if they ever find the spacecraft. 
D) monitor tens of millions of frequencies at once in an effort to detect extraterrestrial radio communications.

Question 17

The meteorite Nakhla is one of several meteorites believed to originate on Mars, which show small tunnel structures similar to Earth rocks inhabited by rock-eating microbes. But Nakhla is special for another reason. What is that reason?

Accepted Answer

A) It was the first meteorite to exhibit such tunnels. 
B) The rock's composition has been traced to a specific crater on Mars. 
C) The fall of this meteorite was observed, so it could not have been contaminated by being on Earth for a long period. 
D) It is a carbonaceous chondrite, and as such contains carbon compounds and volatile materials as a result of never having been heated. 
A) It was the first meteorite to exhibit such tunnels. 
B) The rock's composition has been traced to a specific crater on Mars. 
C) The fall of this meteorite was observed, so it could not have been contaminated by being on Earth for a long period. 
D) It is a carbonaceous chondrite, and as such contains carbon compounds and volatile materials as a result of never having been heated.

Question 18

What is the current state of the search for extraterrestrial radio communications?

Accepted Answer

A) Several extraterrestrial civilizations have been found, but they are not intelligent enough for us to bother with, and the search is continuing. 
B) Several private or university-based searches using existing telescopes and links to millions of private home computers are searching at many frequencies. 
C) Continuous transmissions are being sent out from Earth at several frequencies in the "water hole," and tens of millions of other frequencies are being monitored. 
D) Several dedicated telescopes are continuously monitoring the neighborhoods of nearby stars, which are known to have planets, for bright flashes or coded signals at common visible laser wavelengths. 
A) Several extraterrestrial civilizations have been found, but they are not intelligent enough for us to bother with, and the search is continuing. 
B) Several private or university-based searches using existing telescopes and links to millions of private home computers are searching at many frequencies. 
C) Continuous transmissions are being sent out from Earth at several frequencies in the "water hole," and tens of millions of other frequencies are being monitored. 
D) Several dedicated telescopes are continuously monitoring the neighborhoods of nearby stars, which are known to have planets, for bright flashes or coded signals at common visible laser wavelengths.

Question 19

Which one of Saturn's satellites has been suggested as the site of a subsurface liquid water ocean?

Accepted Answer

A) Enceladus 
B) Iapetus 
C) Pandora 
D) Rhea 
A) Enceladus 
B) Iapetus 
C) Pandora 
D) Rhea

Question 20

Silicon has often been suggested as an alternative to carbon in biochemistry. Each of the following is one reason silicon is unsuitable for such a role EXCEPT ONE. Which is the EXCEPTION?

Accepted Answer

A) Silicon compounds are too soft or too hard to be part of living organisms. 
B) Silicon compounds react too much or too little to be part of living organisms. 
C) Silicon atoms bond with up to four other atoms. 
D) Silicon compounds react too slowly to undergo the rapid changes required of molecules in organisms. 
A) Silicon compounds are too soft or too hard to be part of living organisms. 
B) Silicon compounds react too much or too little to be part of living organisms. 
C) Silicon atoms bond with up to four other atoms. 
D) Silicon compounds react too slowly to undergo the rapid changes required of molecules in organisms.

Exam 27: The Search for Extraterrestrial Life

What is the Allen Telescope Array?

Organic compounds have been found in each of the following EXCEPT ONE. Which is the EXCEPTION?

Why do we believe that some meteorites, such as the Antarctic find ALH 84001, originated on Mars?

If we were able to detect radio signals from an intelligent civilization, we would hope they are doing all of the following things, EXCEPT ONE. What is the EXCEPTION?

A key target in our radio telescope search for exoplanets harboring life is:

Why do we only consider stars with masses less than about 1.5 Me in the Drake equation when estimating the number of possible stars in our galaxy around which planets could form that would support our kind of intelligent life?

In a few decades, orbiting telescopes such as Kepler and James Webb Space Telescope (JWST) may be operational and sending us data. What might these results mean for our use of the Drake equation?

What are amino acids?

Which molecules, whose absorption lines appear in the infrared, are considered most likely to indicate the presence of life if they were detected on any planet orbiting another star?

Some meteorites found on Earth are believed to come from Mars because trapped bits of atmosphere in these meteorites match the composition of Mars's atmosphere. What more can be said about this?

In which of the following environments have long-chain carbon-based molecules not been found?

In what way was volcanism important to the development of life on Earth?

We believe the meteorite ALH 84001 came from Mars because of trace amounts of gas trapped in the rock. What does analysis of this gas reveal?

Several lines of evidence now suggest that large and complex organic molecules, from which the building blocks of life could be formed, have evolved in outer space. Which of the following is NOT one of these observational findings?

The method used in the Urey-Miller experiment was to:

The meteorite Nakhla is one of several meteorites believed to originate on Mars, which show small tunnel structures similar to Earth rocks inhabited by rock-eating microbes. But Nakhla is special for another reason. What is that reason?

What is the current state of the search for extraterrestrial radio communications?

Which one of Saturn's satellites has been suggested as the site of a subsurface liquid water ocean?

Silicon has often been suggested as an alternative to carbon in biochemistry. Each of the following is one reason silicon is unsuitable for such a role EXCEPT ONE. Which is the EXCEPTION?

Astronomy and the Universe

Knowing the Heavens

Eclipses and the Motion of the Moon

Gravitation and the Waltz of the Planets

The Nature of Light

Optics and Telescopes

Comparative Planetology I: Our Solar System

Comparative Planetology II: the Origin of Our Solar System

The Living Earth

Our Barren Moon

Mercury, Venus, and Mars: Terrestrial, yet Unique

Jupiter and Saturn: Lords of the Planets

Jupiter and Saturns Satellites of Fire and Ice

Uranus, Neptune, Pluto, and the Kuiper Belt: Remote Worlds

Asteroids, Comets, and Impacts

Our Star, the Sun

The Nature of the Stars

The Birth of Stars

Stellar Evolution: on and After the Main Sequence

Stellar Evolution: The Death of Stars

Stellar Remnants: Neutron Stars and Black Holes

Our Galaxy

Galaxies

Quasars and Active Galaxies

Cosmology: The Origin and Evolution of the Universe

Exploring the Early Universe

Filters

Why do we only consider stars with masses less than about 1.5 M_e in the Drake equation when estimating the number of possible stars in our galaxy around which planets could form that would support our kind of intelligent life?