Question 1

In the early 1950's, Stanley Miller and Harold Urey conducted a series of pioneering laboratory experiments involving simulations of the early Earth. What did these experiments reveal?
A) that the early Earth was constantly bombarded by asteroids and comets
B) that under the conditions on the early Earth, they could synthesize some of the building blocks of life in a laboratory
C) that the early Earth was much hotter than anyone had suspected
D) that the early Earth had received microscopic life in meteorites that had come from Mars in the very beginning of the solar system's history
E) that the early Earth had to have been covered with a thick layer of ice, just like Jupiter's satellite Europa

Accepted Answer

The Miller-Urey experiments showed that under the conditions on the early Earth, including a reducing atmosphere and electrical discharges, amino acids and other organic compounds could be synthesized in a laboratory setting. This provided evidence for the possibility of abiogenesis, or the formation of life from non-living matter, on the early Earth.

Question 2

In which of the following places have astronomers NOT found evidence for the building blocks of life (organic compounds)?
A) Earth
B) comets
C) meteorites
D) clouds of interstellar gas and dust
E) we have found evidence for such materials in all of the above sites

Accepted Answer

Astronomers have found evidence for the building blocks of life (organic compounds) in all of the above places - Earth, comets, meteorites, and clouds of interstellar gas and dust.

Question 3

When they talk about the Copernican principle, philosophers and astronomers mean that:
A) the idea that Copernicus was the greatest astronomer who ever lived and the model for astronomers ever since
B) the idea that everything in the universe revolves around the Sun
C) the idea that everything in the universe rotates and revolves (i.e. has angular momentum)
D) the idea that there is nothing special about our place in the universe
E) the idea that the universe is expanding in every direction that we look

Accepted Answer

The Copernican principle states that there is nothing special about our place in the universe, and that the laws of physics are the same everywhere. It is based on the idea that Earth is not at the center of the universe, as was believed in ancient times, but rather that we orbit the Sun along with other planets. This idea challenged the existing worldview and helped lay the foundation for modern astronomy.

Question 4

If you wanted to find a type of atom in your little finger that has been in its present form (been the same element) since the beginning of the universe, which element should you look for?
A) hydrogen
B) carbon
C) iron
D) oxygen
E) Einsteinium

Accepted Answer

Hydrogen is the simplest and most abundant element in the universe, and has been present since the beginning of the universe. While other elements may have been created through processes such as fusion in stars, hydrogen is the only element that has been in its present form since the earliest moments of the universe.

Question 5

Chemically, the process leading to life on Earth began with lots of liquid water and
A) helium
B) hydrocarbons (molecules which had hydrogen and carbon)
C) radium and its isotopes
D) molecules containing iron
E) molecules containing iridium

Accepted Answer

Hydrocarbons are necessary building blocks for life as they make up a large part of biomolecules such as carbohydrates, lipids, and nucleic acids. Water also played a crucial role in allowing these molecules to come together and form the first living organisms.

Question 6

Photosynthesis releases a particular gas as a byproduct. This gas is:
A) carbon dioxide
B) oxygen
C) water vapor
D) methane
E) DNA

Accepted Answer

Photosynthesis releases oxygen as a byproduct.

Question 7

One reason that some scientists think that there may be life under the ice-crust of Jupiter's moon Europa is that:
A) Europa is unusually warm on its surface; in some places the climate resembles Hawaii on Earth.
B) Life has already been found on Io, Jupiter's inner-most large moon
C) Life has been found on Earth, at the bottom of the ocean, deriving its energy not from sun-light but from hot mineral-laden vents coming from deeper inside our planet; something similar could happen at the bottom of the ocean on Europa
D) meteorites blasted off Europa have been found on Earth and we detect the building blocks of life inside these meteorites from Europa
E) we are receiving intriguing radio messages from Europa that indicate some form of intelligence lives there

Accepted Answer

Life has been found on Earth, at the bottom of the ocean, deriving its energy not from sun-light but from hot mineral-laden vents coming from deeper inside our planet; something similar could happen at the bottom of the ocean on Europa. This suggests that it is possible for life to exist in the absence of sunlight and thus may potentially exist on Europa beneath its ice-crust.

Question 8

What does the Fermi Paradox say?
A) Given all the time since the Big Bang and all the stars, why has some form of intelligent life in the Galaxy not established a network throughout the Galaxy and visited us?
B) Given the size of the Galaxy, there should be an exact duplicate of the Earth somewhere and we should have found it
C) If life on Earth took a miracle to form, then there should be no life anywhere else
D) If all the planets in our solar system besides Earth are lifeless, then it must follow that most of the planets around other stars are also lifeless and finding life is hopeless
E) When Fermi got ill, he always needed two doctors to diagnose him

Accepted Answer

The Fermi Paradox is the apparent contradiction between the high probability of the existence of extraterrestrial civilizations and the lack of evidence for, or contact with, such civilizations. This paradox raises the question of why, given the vastness of the universe and the billions of years in which life could have evolved, we have not yet encountered any other intelligent civilizations. Choice A summarizes the main idea of the Fermi Paradox.

Question 9

What discovery about Saturn's moon Enceladus has encouraged astronomers to think of that moon as a possible place where life might exist?
A) Enceladus has a strong magnetic field
B) Enceladus has rivers of liquid water flowing on its surface
C) There are radio signals coming from Enceladus which indicate they might be made by intelligent life
D) Enceladus has a thick atmosphere with a significant amount of oxygen
E) There are plumes of salty vapor coming from cracks in Enceladus' surface

Accepted Answer

There are plumes of salty vapor coming from cracks in Enceladus' surface, indicating the presence of a saltwater ocean beneath its icy crust. This ocean could potentially support life, making Enceladus a possible place where life might exist.

Question 10

Photosynthesis was a great step forward in the evolution of life on Earth, because with photosynthesis
A) we have the way in which life on Earth and life on Mars resemble each other
B) life could, for the first time, reproduce (make copies of itself)
C) we have the common ancestor that gave rise to every species of life now on Earth
D) life could extract chemical energy from sunlight
E) life did not have to evolve any further

Accepted Answer

Photosynthesis allowed life to harness and use the energy from sunlight, which was a significant advancement in the ability to obtain energy. This allowed for the growth and development of more complex organisms, and was a turning point in the evolution of life on Earth.

Question 11

Which of the following is a recent (last few decades) discovery that confirms the key idea of the Copernican Principle?
A) that the Earth has a Moon
B) that gravity waves exist
C) that planets around other stars are common
D) that 65 million years ago a large asteroid hit the Earth
E) that people from Eastern Europe are pretty smart

Accepted Answer

The discovery that planets around other stars (exoplanets) are common confirms the key idea of the Copernican Principle, which states that the Earth is not in a unique or privileged position in the universe. This discovery suggests that there could be many other potentially habitable worlds in the universe, and that the conditions that gave rise to life on Earth may not be unique to our planet.

Question 12

Think for a moment about an atom of the element lead (atomic number 82) inside the radio that you listen to in the morning. In which of the following places has this atom probably NOT been during the course of its existence?
A) a previous generation star
B) a supernova explosion
C) the Sun
D) a cloud of gas and dust which would clump to become a star and a family of planets
E) the Earth's crust

Accepted Answer

Lead atoms, like other heavy elements, are formed in the processes that occur in previous generation stars and supernova explosions. These atoms can then become part of gas and dust clouds that form new stars and planets, eventually ending up in places like the Earth's crust. However, an atom of lead that is currently on Earth was not likely part of the Sun after the Sun formed, as there is no process by which atoms from the Earth would become part of the Sun.

Question 13

According to astronomers, which of the following places in the outer parts of our solar system might be a reasonable place for life to exist?
A) in the core of the planet Saturn
B) in the rings of Neptune
C) in the mountains of Pluto
D) under the ice of Jupiter's moon Europa
E) on the surface of some of the smaller members of the Kuiper Belt

Accepted Answer

Europa is thought to have a subsurface ocean of liquid water under its icy crust, which could potentially harbor life. None of the other options have conditions suitable for life as we know it.

Question 14

Scientists think that the life we have on Earth today originated some time between 3.5 and 3.8 billion years ago. Yet the solar system and the Earth are known to be at least 4.5 billion years old. Which of the following is one reason life as we know it had to wait until 3.5 to 3.8 billion years ago to get going?
A) supernovae were exploding near the Sun's location every year back then
B) the Sun was so much cooler when the Earth formed, that the Earth's oceans (and even Mars' oceans) were frozen over for billions of years
C) before 3.8 billion years ago, the Earth was experiencing a period of heavy bombardment, when giant chunks of rock and ice left over from planet formation kept hitting our planet and making it uninhabitable
D) experiments like the one done by Miller and Urey show that life on Earth could not form until plants produced a lot of oxygen for our atmosphere
E) the early solar system was filled with dark matter, and life could not form with so much dark matter around

Accepted Answer

The period of heavy bombardment would have made Earth uninhabitable, so life could not have formed until this subsided. The other answer choices are not supported by scientific evidence.

Question 15

For the complex biochemical reactions of life (as we know it) to happen, a solvent is required. What is that solvent for life on Earth?
A) ammonia
B) methane
C) water
D) carbon dioxide
E) diet Coke or diet Pepsi

Accepted Answer

Water is the universal solvent for life on Earth. It is essential for many biochemical reactions to occur and is involved in the transport of nutrients and waste products in living organisms. Ammonia, methane, carbon dioxide and diet Coke or diet Pepsi are not capable of supporting life as we know it.

Question 16

One place that astronomers think might have had life start long ago is Mars. Which of the following is not a discovery that we have made on Mars so far?
A) observing what looks like dried up river channels from orbiting spacecraft
B) the discovery of organic materials (the chemical building blocks of life, such as amino acids) by spacecraft that have landed
C) the discovery that Mars long ago had plenty of flowing water, from the composition and layering of some of the rocks examined by Mars rovers
D) the discovery of mudstone on Mars, which indicates that ancient Mars may have been more habitable than Mars today
E) the discovery of significant amounts of frozen water on Mars, under the surface

Accepted Answer

While we have found evidence indicating that Mars may have had the conditions necessary for life to start (such as dried up river channels, evidence of flowing water, mudstone, and frozen water), we have not yet discovered organic materials on Mars. However, there have been ongoing investigations into the possibility of finding organic materials on Mars, particularly with the upcoming Mars 2020 mission that will collect rock samples to potentially bring back to Earth for analysis.

Question 17

Which of the following is, to the best of our knowledge, in the habitable zone of its star:
A) a "hot Jupiter" taking 4 days to orbit a G-type main sequence star
B) a planet about 1.05 AU from a G-type main sequence star
C) a Jupiter-mass planet taking 15 years to orbit a K-type main sequence star
D) a planet in an orbit the size of the Earth's around a red giant star
E) all of the above

Accepted Answer

The habitable zone refers to the region around a star where conditions are suitable for liquid water to exist on the surface of a planet. Option A describes a "hot Jupiter," which is a gas giant planet that orbits very close to its star and is likely too hot for liquid water. Option C describes a Jupiter-mass planet, which may also be too massive to support life as we know it. Option D describes a planet orbiting a red giant star, which is generally considered unlikely to support life due to the star's stage in its life cycle. Option B is the best choice as it describes a planet at a distance from a G-type main sequence star that is within the habitable zone.

Question 18

Astronomers have discovered a planet orbiting Proxima Centauri, the star closest to the Sun. This is a star of spectral type M, with 12% the mass of the Sun and 15% the size of the Sun. The habitable zone around this star would be
A) much larger (wider) than the Sun's
B) much closer to the star than the Sun's
C) in about the same place as the Sun's asteroid belt
D) much more narrow (small) than the diameter of any planet
E) the source of all the UFO's that have been reported by UFO believers on Earth

Accepted Answer

The habitable zone around Proxima Centauri would be much closer to the star than the Sun's, due to its smaller size and lower luminosity. This means that planets within the habitable zone would need to orbit much closer to the star in order to receive sufficient warmth for liquid water to exist on their surfaces.

Question 19

Scientists are impressed with extremophiles, life forms that can survive under what seems to humans to be extremely unpleasant conditions. In which of the following environments have we not found life:
A) temperatures near or below the freezing point of water
B) temperatures near or above the boiling point of water
C) very acid environments
D) conditions where the radiation dosage is high
E) conditions resembling the photosphere of the Sun
Section 30.3: Searching for Life Beyond Earth

Accepted Answer

Conditions resembling the photosphere of the Sun are too extreme for any known life form to survive.

Question 20

From a scientific perspective, which of the following statements about life elsewhere in the universe is best supported by current evidence?
A) we have good evidence that life exists on many planets around other stars
B) we only have evidence that life exists around three other stars
C) the government has evidence (which it is not releasing) that there is at least one other intelligent life form on a planet orbiting another star
D) while we have evidence of the building blocks of life elsewhere in the universe, we have no definite evidence about life around other stars at this time
E) there is no evidence for intelligent life anywhere, even on Earth
Section 30.2: Astrobiology

Accepted Answer

While we have discovered the building blocks of life on other planets and moons in our solar system, as well as the potential for habitable environments, we have not yet found any definitive evidence of current or past life beyond Earth.

Quiz 30: Life in the Universe

In the early 1950's, Stanley Miller and Harold Urey conducted a series of pioneering laboratory experiments involving simulations of the early Earth. What did these experiments reveal?

In which of the following places have astronomers NOT found evidence for the building blocks of life (organic compounds) ?

When they talk about the Copernican principle, philosophers and astronomers mean that:

If you wanted to find a type of atom in your little finger that has been in its present form (been the same element) since the beginning of the universe, which element should you look for?

Chemically, the process leading to life on Earth began with lots of liquid water and

Photosynthesis releases a particular gas as a byproduct. This gas is:

One reason that some scientists think that there may be life under the ice-crust of Jupiter's moon Europa is that:

What does the Fermi Paradox say?

What discovery about Saturn's moon Enceladus has encouraged astronomers to think of that moon as a possible place where life might exist?

Photosynthesis was a great step forward in the evolution of life on Earth, because with photosynthesis

Which of the following is a recent (last few decades) discovery that confirms the key idea of the Copernican Principle?

Think for a moment about an atom of the element lead (atomic number 82) inside the radio that you listen to in the morning. In which of the following places has this atom probably NOT been during the course of its existence?

According to astronomers, which of the following places in the outer parts of our solar system might be a reasonable place for life to exist?

For the complex biochemical reactions of life (as we know it) to happen, a solvent is required. What is that solvent for life on Earth?

One place that astronomers think might have had life start long ago is Mars. Which of the following is not a discovery that we have made on Mars so far?

Which of the following is, to the best of our knowledge, in the habitable zone of its star:

Astronomers have discovered a planet orbiting Proxima Centauri, the star closest to the Sun. This is a star of spectral type M, with 12% the mass of the Sun and 15% the size of the Sun. The habitable zone around this star would be

Scientists are impressed with extremophiles, life forms that can survive under what seems to humans to be extremely unpleasant conditions. In which of the following environments have we not found life:

From a scientific perspective, which of the following statements about life elsewhere in the universe is best supported by current evidence?