For the first time, a sugar molecule, erythrulose, has been spotted outside our Solar System. This small molecule, composed of four carbon atoms, is also found in raspberries on Earth. Its presence was detected in an interstellar gas cloud located near the center of the Milky Way, named G+0.693-0.027.
To identify this sugar, astronomers used two Spanish radio telescopes: the 40-meter Yebes telescope and the 30-meter IRAM telescope. The signal of erythrulose was confirmed by comparing observations with precise laboratory measurements. The results were published in
Nature Astronomy on July 13.
Sugars are essential molecules for life as we know it. They provide energy, build important biological structures, and are part of the composition of genetic material. Until now, scientists thought that erythrulose could not form in sufficient quantities under the conditions of the primitive Earth. However, its presence in an interstellar cloud indicates that it could form easily on dust grains in space.
Furthermore, sugars such as ribose and glucose have already been found in meteorites and asteroid samples, notably those brought back by the OSIRIS-REx mission from Bennu. The discovery of erythrulose in the interstellar medium indicates that the sugary ingredients of life may be far more widespread than previously thought. They could have been incorporated into Earth during its formation.
This molecule is particularly interesting because it can modify the configuration of threose, another sugar considered a precursor of the first nucleic acids that led to RNA and DNA. Thus, erythrulose could play a key role in the very first stages of chemical evolution toward life.
The next step for scientists is to search for even more elaborate sugars and direct precursors of RNA. They want to understand how far prebiotic chemistry can progress before the formation of planets.
Prebiotic chemistry in space
Prebiotic chemistry studies the reactions that may have led to the emergence of life on Earth, starting from simple molecules. In space, clouds of gas and dust harbor a wide variety of organic compounds, including sugars, amino acids, and nitrogenous bases. These molecules often form on the surface of interstellar dust grains, under the effect of cosmic radiation and extremely low temperatures.
Astronomers use radio telescopes to detect these molecules thanks to their unique spectral signatures. Each molecule emits or absorbs electromagnetic waves at specific frequencies, like a fingerprint. By comparing observations with laboratory spectra, compounds can be identified even light-years away.
The discovery of erythrulose in an interstellar cloud shows that elaborate sugars can form spontaneously in space. These molecules could then be incorporated into planets during their formation, thus providing building blocks for life. This idea reinforces the hypothesis that the ingredients of life are common in the cosmos.