Key sugar for life on Earth could have formed in space | Science News for Students

Key sugar for life on Earth could have formed in space

Lab experiment shows that a sugar key to genetic material on Earth can form on ice around young stars
May 2, 2016 — 7:00 am EST
Carina Nebula

A sugar found in all cells might form on ice grains irradiated by ultraviolet light in stellar nurseries such as the Carina Nebula. Part of that nebula appears in this Hubble Space Telescope image.


An essential ingredient for life as we know it might have formed in space. Later, it might have rained down on a young Earth. That’s the finding of a new study.

The ingredient is the simple sugar ribose (RY-bose). It is a crucial piece of the chemical machinery inside cells. This sugar can form when a blend of ices are blasted with ultraviolet radiation. That’s what Cornelia Meinert and her colleagues reported April 8 in Science. Meinert is a chemist at University Nice Sophia Antipolis in France.

The ices that her term worked with are common on comets. Scientists believe they also coat the grains of interstellar dust that swirl around young stars.

“This is an amazing result,” says Conel Alexander. He is a planetary scientist at the Carnegie Institution for Science in Washington, D.C. For years researchers have been looking at ices exposed to radiation. Yet none, he notes, has ever seen ribose show up. Ribose is the backbone of RNA, a molecule that helps carry out the instructions encoded in genes. RNA is found in all life on Earth. It might have evolved billions of years ago, before DNA.

Other pieces of biological machinery have been found in space. Some have been produced in a lab in ways similar to what might happen in space. Last year, for instance, researchers created uracil (YUR-uh-sil), cytosine (SY-to-seen) and thymine (THY-meen) under conditions that simulated space. These chemicals are three of the molecular letters in the genetic alphabets of DNA and RNA. Researchers also have found amino acids in meteorites. Those molecules link together to form proteins. And in 2014, scientists spied isopropyl (EYE-so-PRO-pul) cyanide (SY-uh-nyde) in a gas cloud near the center of our galaxy. This molecule resembles amino acids. A decade earlier, scientists found the simple sugar glycoaldehyde (GLY-ko-AL-duh-hyde) in the same cloud.

Meinert and her colleagues started with water, ammonia and methanol. Each exists in comets as ices. The researchers cooled the substances to –195° Celsius (–319° Fahrenheit) inside a vacuum chamber. They then simulated the radiation given off by a young star by exposing the ice to ultraviolet light. Later, the cosmic goop was warmed back to room temperature.

The researchers then examined chemicals that had formed on the ice. They found about 55 different organic (or carbon-based) molecules. Ribose was one of them.

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space sugar

The results aren’t too surprising, says Reggie Hudson. He is a chemist at NASA’s Goddard Space Flight Center in Greenbelt, Md. Researchers had suspected sugars could form on interstellar ice. And the chemistry at work here has been understood for 155 years, he says. But no one had actually done the experiment before.

One challenge: The compounds that formed are really common. People carry many of the sugars in their bodies. And one chemical that turned up is ethylene glycol (ETH-uh-leen GLY-kol). It’s best known as antifreeze. Any of these could have accidentally contaminated the experiment. To probe for signs of that, the researchers used methanol ice that contained a type of atoms known as carbon-13. Any contaminants would have carried the more common carbon-12. By seeing carbon-13 show up in the ribose and other sugars, the researchers could be sure that these were due to chemical reactions in the ice.

It is, however, hard to tell whether the molecules formed when the ices were cold or as the samples warmed up, notes Hudson. The study’s authors agree. But both Hudson and Meinert point out that warm temperatures can occur around interstellar ice grains. Young stars will periodically warm the belts of debris that surround them. And grains that fall to Earth will heat up as they fall through Earth’s atmosphere. Instead of forming in space, then, ribose might have formed as its ingredients rained down upon Earth.

No one has seen ribose in comets or asteroids. A few upcoming missions, however, might get a chance to look for it. Japan’s Hayabusa2 spacecraft is on course to pilfer material from asteroid (162173 Ryugu). And NASA’s OSIRIS-REx mission will launch in September. It will bring pieces of an asteroid named Bennu back to Earth.

Power Words

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amino acids    Simple molecules that occur naturally in plant and animal tissues and that are the basic constituents of proteins.

ammonia   A colorless gas with a nasty smell. Ammonia is a compound made from the elements nitrogen and hydrogen. It is used to make food and applied to farm fields as a fertilizer. Secreted by the kidneys, ammonia gives urine its characteristic odor. The chemical also occurs in the atmosphere and throughout the universe.





carbon-12    The most abundant form of carbon. Each of its atoms has 6 protons and 6 neutrons in the nucleus. This isotope of carbon has a lower weight than carbon-13.

carbon-13    A carbon atom with 6 protons and 7 neutrons in the nucleus. This isotope of carbon has a magnetic spin that allows researchers to detect its presence.






debris    Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft. 

encode       (adj. encoded) To use some code to mask a message.


interstellar    Between stars.

meteor    A lump of rock or metal from space that hits the atmosphere of Earth. In space it is known as a meteoroid. When you see it in the sky it is a meteor. And when it hits the ground it is called a meteorite.  

methanol    A colorless, toxic, flammable alcohol, sometimes referred to as wood alcohol or methyl alcohol. Each molecule of it contains one carbon atom, four hydrogen atoms and an oxygen atom. It is often used to dissolve things or as a fuel.



nucleotides    The four chemicals that, like rungs on a ladder, link up the two strands that make up DNA. They are: A (adenine), T (thymine), C (cytosine) and G (guanine). A links with T, and C links with G, to form DNA. In RNA, uracil takes the place of thymine.

organic    (in chemistry) An adjective that indicates something is carbon-containing; a term that relates to the chemicals that make up living organisms. (in agriculture) Farm products grown without the use of non-natural and potentially toxic chemicals, such as pesticides.

planet   A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish        ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

planetary science    The science of other planets besides Earth.



ribose   A type of sugar that forms the backbone for RNA.




stellar   An adjective that means of or relating to stars.


vacuum    Space with little or no matter in it. Laboratories or manufacturing plants may use vacuum equipment to pump out air, creating an area known as a vacuum chamber. 


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Further Reading

Read another version of this story on Science News.

S. Ornes. “Asteroid impacts may have sparked life on Earth.” Science News for Students. December 29, 2014.

A. Yeager. “Comet probe may shed light on Earth’s past.” Science News for Students. November 13, 2014.

S. Ornes. “Space cloud may hold clue to life’s origins.” Science News for Students. October 13, 2014.

S. Ornes. “Explainer: What are asteroids?Science News for Students. August 26, 2014.

Original Journal Source: C. Meinert et al. Ribose and related sugars from ultraviolet irradiation of interstellar ice analogsScience. Vol. 352, April 8, 2016, p. 208. doi: 10.1126/science.aad8137.