Some life blocks found on the comet 67P/Churyumov-Gerasimenko

The comet 67P/Churyumov-Gerasimenko photographed on March 25, 2015, one of the moments of the organic molecules detections (Photo ESA/Rosetta/NavCam – CC BY-SA IGO 3.0)
The comet 67P/Churyumov-Gerasimenko photographed on March 25, 2015, one of the moments of the organic molecules detections (Photo ESA/Rosetta/NavCam – CC BY-SA IGO 3.0)

An article published in the journal “Science Advances” describes the discovery of ingredients that are considered key to the origin of life on Earth on the comet 67P/Churyumov-Gerasimenko. In particular, glycine, an amino acid found in proteins, and phosphorus, an element that forms DNA and cell membranes. These observations were made by the ROSINA instrument aboard ESA’s Rosetta space probe.

For many years, scientists have been trying to find out which organic molecules and elements crucial for Earth’s life forms are present on comets. Glycine was found in samples taken by the Stardust space probe from the comet Wild-2 but there was the possibility that there was a contamination. This time the detection was made on the spot, in the coma emitted by the comet 67P/Churyumov-Gerasimenko, starting from October 2014 with most carried out in August 2015, during the perihelion passage.

Kathrin Altwegg, lead author of this research but also principal investigator of the ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instrument, also explained that other organic molecules were detected such as methylamine and ethylamine, which can be glycine precursors. They offer more clues about the ways in which this amino acid may form.

Glycine was detected along with dust and that means it probably was ejected together with other volatile compounds from the frozen dust mantle that got heated with the approach of the comet 67P/Churyumov-Gerasimenko to the Sun. This amino acid turns into gas only at temperatures near 150° Celsius (about 302° Fahrenheit) so it’s unlikely that this can happen at the temperature on the surface and in the comet’s coma. This explains why it was detected only occasionally.

Even the phosphorus detection is important because that’s an element crucial for Earth’s life forms. It’s used for example in the DNA structure and cell membranes but has also other functions in the metabolism of living organisms.

It’s another piece of the puzzle that concerns the birth of life on Earth and confirms the possibility that at least part of the ingredients that made it came from comets. That’s the reason why there’s so much interest about the presence of organic compounds in comets.

In the case of 67P/Churyumov-Gerasimenko in November 2014 the first unofficial news on the detection of organic molecules by the Philae lander already leaked. In that case the data were limited while the Rosetta space probe was able to carry out many detections over the course of its mission.

Comets kept their chemical characteristics almost unchanged compared to 4.5 billion years ago, when the solar system was born. The discovery of organic molecules was one of the Rosetta mission’s goals and it was reached. There’s still much to discover about the link between comets and the birth of life on Earth but now we have some more information about it.

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