Comet 67P contains ingredients for life

Were the ingredients that kick-started life on Earth delivered by a comet or asteroid crash-landing on our planet? New data from ESA's Rosetta mission has revealed this could have been the case.

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An outburst of dust and gas can be seen emanating from Comet 67P as it approaches perihelion on 12 August 2015. Analysis of these outbursts revealed traces of glycine: an amino acid fundamental to the formation of life as we know it.
Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

ESA’s Rosetta mission has detected ingredients crucial for the formation of life on Comet 67P.

The spacecraft has been studying Comet 67P/Churyumov-Gerasimenko for nearly two years and has made repeat detections of chemicals key to the formation of life, adding to the debate as to whether asteroids and comets are responsible for kick-starting life on Earth.

Two of the ingredients detected by Rosetta are glycine, an amino acid commonly found in proteins, and phosphorus, a component of DNA and cell membranes.

The results confirm that comets at least have the potential to deliver the components for life to form on a planet, although it is not yet clear whether this is the case with Earth.

Traces of glycine were previously found in samples taken of Comet Wild-2 by NASA’s Stardust mission in 2006, but potential contamination of the samples made analysis difficult.

Now, data sent back by Rosetta has confirmed the detection of glycine in the coma of Comet 67P.

“This is the first unambiguous detection of glycine at a comet,” says Kathrin Altwegg, principal investigator of the ROSINA instrument that made the measurements. “At the same time, we also detected certain other organic molecules that can be precursors to glycine, hinting at the possible ways in which it may have formed.”

The measurements that led to the detection were made just before Comet 67P reached perihelion – the closest point to the Sun in its orbit – in August 2015. The first was made in October 2014 and the next during a flyby in March 2015. Dusty outbursts from below the comet’s surface also revealed the presence of glycine in the month leading up to perihelion.

“We see a strong link between glycine and dust, suggesting that it is probably released perhaps with other volatiles from the icy mantles of the dust grains once they have warmed up in the coma,” says Altwegg.

The detection by Rosetta of phosphorous is also a key revelation. Phosphorus is found in the structural framework of DNA and in cell membranes, and is thus a key element in the formation life as we know it.

“There is still a lot of uncertainty regarding the chemistry on early Earth and there is of course a huge evolutionary gap to fill between the delivery of these ingredients via cometary impacts and life taking hold,” says study co-author Hervé Cottin.

“But the important point is that comets have not really changed in 4.5 billion years: they grant us direct access to some of the ingredients that likely ended up in the prebiotic soup that eventually resulted in the origin of life on Earth.”

“The multitude of organic molecules already identified by Rosetta, now joined by the exciting confirmation of fundamental ingredients like glycine and phosphorous, confirms our idea that comets have the potential to deliver key molecules for prebiotic chemistry,” says Matt Taylor, ESA’s Rosetta project scientist.

“Demonstrating that comets are reservoirs of primitive material in the Solar System and vessels that could have transported these vital ingredients to Earth, is one of the key goals of the Rosetta mission, and we are delighted with this result.”


Carousel image: Image of Comet 67P/Churyumov–Gerasimenko captured by Rosetta’s OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached perihelion.
Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
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