Extract from ABC News
Chemical signatures of a sugar called erythrulose have been detected near the centre of the Milky Way. (Supplied: NASA, JPL-Caltech, Susan Stolovy (SSC/Caltech) et al.)
In short:
Astronomers say they've detected true sugar in interstellar space for the first time.
Erythrulose is a simple sugar found in raspberries and used in self-tanning lotions.
The astronomers say the discovery provides clues about how sugars may have formed in the universe and became building blocks of life on Earth.
Astronomers have detected signs of a type of sugar in gas clouds near the centre of our galaxy, the Milky Way.
Sugars provide energy and are key building blocks of life on Earth, such as DNA, but how they got here is a mystery.
It's not uncommon to find sugar in the cosmos — simple sugars such as ribose and glucose have been previously discovered on asteroids in our Solar System.
But this is the first time sugar molecules have been found beyond our Solar System in the interstellar medium, astronomers report in Nature Astronomy.
They found the chemical fingerprint of erythrulose (C4H8O4), which contains four carbon molecules, and is a type of sugar known as a ketose.
On Earth, it is found in raspberries and is used as an ingredient in self-tanning lotions.
The study's lead author, Izaskun Jiménez-Serra, of the Center for Astrobiology CSIC-INTA in Spain, said the detection of erythrulose tells us that these compounds may be more universal than what we originally thought.
"The detection of the first sugar in interstellar space suggests that the key ingredients for life can form in molecular nebula before stars and planets form," Dr Jiménez-Serra said.
Finding sugar in interstellar space
Dr Jiménez-Serra and colleagues detected the chemical signs of the sugar in a large cloud of gas and dust called G+0.693-0.027 in data captured by two radio telescopes in Spain.
They then analysed the signature of the molecule in the laboratory using spectroscopy to identify chemicals by their microwave length.
The astronomers used data from the Yebes 40m (pictured) and IRAM 30-metre radio telescopes. (Wikimedia: Yebesoan)
The match is so good, there is no doubt the astronomers have detected erythrulose, said Evan Bieske, a professor of chemistry at the University of Melbourne who was not involved with the study.
But don't get too excited about the prospect of raspberries in space.
"Rather, its existence in space is an indication that relatively complex molecules [some of which have biological roles on Earth] can be synthesised through abiotic chemical reactions in giant molecular clouds," Professor Bieske said.
He also said there were mirror versions of the molecule, and it was unclear from spectroscopy whether the one found in space was the same as the one found on Earth.
Erythrulose is a sugar that contains four carbon atoms four oxygen atoms, and eight hydrogen atoms. (Supplied: Jiménez-Serra et al. Nature Astronomy)
It is not the first time that astronomers have found a chemical similar to sugar near the centre of our galaxy.
More than two decades ago, astronomers detected the fingerprint of a compound called glycoaldehyde.
The authors of the new study also found glycoaldehyde at similar levels to erythrulose in the gas cloud.
Glycoaldehyde, which contains two carbon atoms, has a similar structure to sugars, but it is not considered a "true sugar", Dr Jiménez-Serra said.
"It is not considered a sugar because it lacks the minimum number of three carbons and functional groups biochemists require to form stable, ring-shaped structures."
But, she said, it could contribute to the formation of four-carbon sugars such as erythrulose in icy interstellar space.
"Erythrulose forms on the surface of interstellar dust grains by the chemical reaction of glycolaldehyde and ethylene glycol, with two carbon atoms each, as if two big Lego blocks got together."
Sugar and space dust
So far, more than 350 different chemicals have been detected in interstellar space.
How they form has been an active area of research since 1937, when the first molecules were found.
Professor Bieske said the dust hypothesis put forward by the researchers was plausible.
One way molecules can form more complex compounds is by literally bumping into each other.
But it is hard to do this in the freezing void of space.
"Chemistry in space is like nothing on Earth,"Professor Bieske said.
"Temperatures and densities are very low so that molecules rarely encounter one another, although the encounter rate is enhanced if one of the reactants has a charge," he said.
Even if two smaller molecules did meet, building larger molecules is challenging because the larger molecule needs to release energy, or it will decompose.
On Earth, this energy would be removed by a third molecule or atom, Professor Bieske explained.
But in space, the chance of a chemical trio is slim.
The alternative is to hook up with a dust particle.
"Dust particles have icy mantles containing various smaller reactant molecules that diffuse across the surface to form more complex molecules in reactions driven by UV light or cosmic rays."
When the UV light or cosmic rays heat the particle, the icy surface evaporates, releasing the molecules into space.
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