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?

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)?

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:

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?

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

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:

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:

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?

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?

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

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?

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?

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?

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?

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?

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?

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:

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

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:

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?

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