Miller and Urey Go to Outer Space

Chapter 10. Miller and Urey Go to Outer Space

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As our planet orbits the sun, it sweeps up more than 100 tons of dust every day. This doesn’t include larger rocks and debris, which occasionally light up the night sky as meteors. While most rocks burn up in the atmosphere, remnants occasionally survive and make it to the surface. This has led some researchers to suggest our planet could have been seeded by stardust. However, scientists like Charles Darwin and Nobel Laureate Harold Urey proposed a different theory: they suggested the building blocks of life formed when lightning struck an atmosphere rich with chemicals.

Which theory makes the most sense? Let’s take a closer look.

The primordial soup

In 1871 Charles Darwin, the father of evolution, wrote a letter to botanist Joseph Hooker suggesting that life may have arisen from simple chemical ingredients. Though Darwin acknowledged he was speculating, he envisioned a primordial soup environment consisting of “a warm little pond with all sorts of ammonia and phosphoric salts, light, heat, electricity, etc., present...”

In 1953, Stanley Miller (shown in here in the laboratory) and his advisor Harold Urey created a "warm little pond" inside a glass apparatus and successfully generated organic molecules from hydrogen, ammonia, and methane, demonstrating that basic building blocks of life could form from simple chemical compounds.

In 1953, University of Chicago graduate student Stanley Miller created a “warm little pond” inside a U-shaped glass apparatus, and successfully demonstrated that the building blocks of life could form from simple chemicals.

Miller’s advisor, chemist Harold Urey, believed the early atmosphere, like Jupiter, contained lots of hydrogen (H2), ammonia (NH3), and methane (CH4). Miller’s apparatus mixed these gasses with water vapor, delivered shocks of electricity from electrodes, and then emptied the mixture back into a boiling flask. The experiment generated several amino acids, principally alanine and glycine. As more sophisticated analytical methods developed, future experiments detected additional amino acids.

After Miller’s death in 2007, several boxes containing vials of dried residue were found by his friends, Antonio Lazcano of the National Autonomous University of Mexico, and Jeff Bada, a professor at the Scripps Institution of Oceanography at the University of California - San Diego. The residue had been left unanalyzed from early experiments, and Miller’s friends decided to use modern techniques to search for the chemical building blocks of life. After joining forces with Jason Dworkin and his colleagues at NASA, the team discovered 22 amino acids in these samples, including at least five amino acids never detected by Miller.

Life As We Know It

Amino acids are important molecular building blocks of life. They are tiny compounds capable of forming long chains. When chains of a particular sequence of amino acids get lengthy, they twist and convolute. The result is a protein. Proteins pump nutrients into our cells, regulate blood sugar, and make muscles contract. Life as we know it couldn’t exist without them!

Miller and Urey in space

In 1969 the Murchison Meteorite plummeted to the earth in southern Australia. After grinding up bits of the rock for chemical analysis, scientists were surprised to find amino acids.

Unlike the amino acids on earth, most of those found in the meteorite also contained deuterium, or heavy hydrogen. As the water in the meteorite contained little deuterium, some thought the amino acids formed on the larger parent body from which the meteorite originated.

The Murchison Meteorite, part of which is pictured here, crashed to earth in southern Australia in 1969. Scientists who analyzed the meteorite were surprised to discover amino acids containing deuterium, which is not found in amino acids on earth.

NASA scientist Max Bernstein proposed a different hypothesis. As the meteorite swept through dust clouds on its way to earth, it might have picked up several different types of amino acids. These extra-terrestrial amino acids may have formed when ultraviolet light hit the chemicals and deuterium-rich water. Astronomers discovered the water in the matter that exists between star systems in the galaxy, called the interstellar medium.

Bernstein conducted an experiment like Miller’s, only he used deuterium-rich water and freezing chambers to recreate the cold, volatile environment found in dense molecular clouds. The amino acids glycine, alanine, and serine emerged from the frosty concoction.

“Of course we didn’t produce organisms, just the building blocks used by life,” says Bernstein. “But this shows these components could have formed in the extraterrestrial environment.”

Molecules from space?

Billions of years ago there was far more debris in the solar system than there is today. Rocks the size of a small moon skirted around the Sun. Gradually, matter began to collide with larger bodies, transforming planets and moons into their familiar sizes.

While the solar system was still condensing, this debris bombarded the early earth. If molecules beneath the surface of the debris were able to withstand the heat of sailing through the earth’s atmosphere, it is feasible that these same molecules may have contributed extraterrestrial components to early life forms.

So both theories have credence. In fact, life on earth may have arisen from Darwin’s primordial soup, seasoned with a bit of stardust.

Analyzing Space Dust

Did you know that NASA mission OSIRIS-REx will launch in 2016 to collect samples of space dust from asteroid 1999 RQ36? Samples with be analyzed on the spacecraft using robotics and then taken to earth for additional experiments. The goal is to analyze dust for organic compounds without the problems of contamination and alteration introduced when meteorites hit the ground. Find out more at Did you know that NASA mission OSIRIS-REx will launch in 2016 to collect samples of space dust from asteroid 1999 RQ36? Samples with be analyzed on the spacecraft using robotics and then taken to earth for additional experiments. The goal is to analyze dust for organic compounds without the problems of contamination and alteration introduced when meteorites hit the ground. Find out more at http://osiris-rex.lpl.arizona.edu/

© 2015 WH Freeman and Company.

Answer the questions below to demonstrate your understanding of the article.

1.

True/False:

The setup of Miller and Urey’s experimental apparatus was largely based upon a theory proposed by Charles Darwin.

True. The conditions Miller and Urey produced within their glass apparatus were mimicking those conditions thought to have existed on early earth. Darwin had proposed that life developed in a “primordial soup” environment, which guided Stanley Miller and Harold Urey in their development of the environmental conditions within the glass apparatus.
Incorrect. The answer is True. The conditions Miller and Urey produced within their glass apparatus were mimicking those conditions thought to have existed on early earth. Darwin had proposed that life developed in a “primordial soup” environment, which guided Stanley Miller and Harold Urey in their development of the environmental conditions within the glass apparatus.

2.

What elements did Urey and Miller combine in their apparatus to generate the organic building blocks of life? Choose ALL that apply.

hydrogen

ammonia

lithium

methane

deuterium

Correct. The scientists believed earth’s early atmosphere contained hydrogen, ammonia, and methane.
Not quite. The scientists believed earth’s early atmosphere contained hydrogen, ammonia, and methane.

3.

The chemicals in Miller and Urey’s glass apparatus were exposed to , which initiated chemical reactions leading to the formation of amino acids.

2
Correct. Scientists, including Miller, Urey, and Charles Darwin, strongly believed that the building blocks of life formed after lightning struck early earth’s chemical-rich atmosphere. To replicate this, Miller and Urey exposed chemicals in their apparatus to electrical shocks.
Try again. You have one attempt remaining.
Incorrect. Scientists, including Miller, Urey, and Charles Darwin, strongly believed that the building blocks of life formed after lightning struck early earth’s chemical-rich atmosphere. To replicate this, Miller and Urey exposed chemicals in their apparatus to electrical shocks.

4.

Why was it significant that Miller and Urey’s experiment generated several different kinds of amino acids?

A.
B.
C.
D.
E.
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Amino acids and proteins are crucial to all life on our planet. Being able to generate these amino acids from several basic elements plus water vapor suggested that early life on earth likely arose in a similar way.
Try again. You have one attempt remaining.
Incorrect. Amino acids and proteins are crucial to all life on our planet. Being able to generate these amino acids from several basic elements plus water vapor suggested that early life on earth likely arose in a similar way.

5.

Which statement below best explains how extraterrestrial dust may have contributed to the development of life on earth?

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B.
C.
D.
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Some scientists have postulated that space dust containing amino acids, the building blocks of life, may have been the basis of life on earth.
Try again. You have one attempt remaining.
Incorrect. Some scientists have postulated that space dust containing amino acids, the building blocks of life, may have been the basis of life on earth.

6.

Why was it only after Miller’s death in 2007 that additional amino acids were discovered from his 1952 experiments?

A.
B.
C.
D.
E.
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Correct. After Miller’s death, his friends discovered unanalyzed vials containing residue, where they discovered a total of 22 amino acids—including 5 not detected by Miller’s experiments.
Try again. You have one attempt remaining.
Incorrect. After Miller’s death, his friends discovered unanalyzed vials containing residue, where they discovered a total of 22 amino acids—including 5 not detected by Miller’s experiments.

7.

Scientists were surprised to discover amino acids when they ground up small samples of the Murchison Meteorite that crashed into the earth in 1969. Of the answers listed below, which two correctly describe explanations proposed by scientists for the origin of these amino acids?

The meteorite was exposed to high levels of heat upon entering earth’s atmosphere, which catalyzed chemical reactions, producing amino acids.

Amino acids formed on a larger parent rock from which the meteorite broke free before being carried to earth.

The meteorite was exposed to extreme low temperatures that could have catalyzed chemical reactions, producing amino acids.

An asteroid collided with an unknown planet, breaking off pieces that had amino acids in them, which then fell to earth.

The meteorite swept through extraterrestrial dust clouds on its way to earth, and it picked up amino acids that formed in space along the way.

Right. One group of scientists postulated that amino acids had formed on a larger parent rock from which the Murchison Meteorite had broken free, while a NASA researcher proposed that the meteorite picked up amino acids formed in space as it swept through dust clouds.
Not quite. One group of scientists postulated that amino acids had formed on a larger parent rock from which the Murchison Meteorite had broken free, while a NASA researcher proposed that the meteorite picked up amino acids formed in space as it swept through dust clouds.

8.

What was the significance of discovering deuterium in the amino acids found in the Murchison Meteorite?

A.
B.
C.
D.
E.
2
Correct. Deuterium acts as a marker for the amino acids’ origin.
Try again. You have one attempt remaining.
Incorrect. Deuterium acts as a marker for the amino acids’ origin.

9.

NASA scientist Max Bernstein conducted experiments similar to those of Stanley Miller and Harold Urey, except he ___________

A.
B.
C.
D.
E.
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Bernstein used deuterium-rich water and other materials in his test chamber to create cold, dense molecular clouds, allowing him to test whether or not amino acids could form under such conditions.
Try again. You have one attempt remaining.
Incorrect. Bernstein used deuterium-rich water and other materials in his test chamber to create cold, dense molecular clouds, allowing him to test whether or not amino acids could form under such conditions.

10.

In 2016, NASA will launch OSIRIS-REx to collect samples of space dust from asteroid 1999 RQ36. Why is it important to actually land on and collect samples from the asteroid in space instead of collecting samples from debris that has crashed into earth’s surface?

A.
B.
C.
D.
E.
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Correct. It still is unknown how the formation (or collection) of amino acids is affected by space debris passing through earth’s atmosphere or crashing to its surface. Conducting this research by collecting samples directly from the surface of the asteroid will help scientists answer that question.
Try again. You have one attempt remaining.
Incorrect. It still is unknown how the formation (or collection) of amino acids is affected by space debris passing through earth’s atmosphere or crashing to its surface. Conducting this research by collecting samples directly from the surface of the asteroid will help scientists answer that question.

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