The figure shows the Rosetta spacecraft orbiting the Comet 67P/Churyumov-Gerasimenkoin (credit ESA). Rosetta was the first spacecraft ever to orbit the nucleus of a comet (ESA. 2014)

  1. Comets are celestial objects formed at the time of the creation of our Solar System in the furthest regions of it. They are one of the most primitive forms of extraterrestrial bodies (NASA 1978).
  2. Several missions in the past have revealed the presence of some organic compounds and other crucial elements in life formation on comets’ surfaces (Elsila et al. 2009, Altwegg et al. 2016) and many physicists believe that life might have been brought to Earth by cometary activity. 

Comets consist mainly of frozen gases that melt away when they are orbiting near the Sun leaving behind the famous comet tail. They are considered to be debris of the very early stages of the Solar System and for this reason, scientists have always shown a great interest in studying their relation to the evolution of life on Earth. The most famous project involving the study of the material composition of a comet was the Rosetta mission (ESA 1993, Bibring et al. 2015) which started gathering data from the Comet 67P/Churyumov-Gerasimenkoin in 2014 under the operation of the European Space Agency (ESA). 

The belief that life on Earth was brought by cometary materials is known as “cometary panspermia” (Wickramasinghe 2011). Currently, there have been several interesting findings in support for this hypothesis. In 2009, for the first time, NASA scientists found on a comet an essential amino-acid for the creation of life; Glycine (Elsila et al. 2009). The Rosetta mission later found glycine together with the substrates for formation, methylamine, and ethylamine (Altwegg et al. 2016). The spectrometry applied on cometary material from 67P/Churyumov-Gerasimenko revealed small levels of hydrogen cyanide, hydrogen sulfide and phosphorus (Altwegg et al. 2016). The most appealing part of scientists of the mission was the presence of phosphorus, as it is known to be a key component of DNA (Watson and Crick 1953). Although more than 16 organic molecules have been discovered on cometary materials (Altwegg et al. 2016), scientists have yet to see micro-organisms on a comet. Discovering micro-organisms would be the ultimate evidence that life really originated from comets.

The discovery of organic molecules on comets is not only a key to better perceive the origin of life on our planet but also implies that life might have been triggered in similar ways in other corners of our Solar System too. Based on the evidence published by NASA and ESA, scientists unanimously believe that comets, these primitive objects of the Solar System are a valuable source of information to understand where we come from.  

COPYRIGHT: This article is the property of We Speak Science, a nonprofit institution co-founded by Dr. Detina Zalli (Harvard University) and Dr. Argita Zalli (Imperial College London). The article is written by Bianka Mecaj, MSc in Physics ETH Zurich-Ecole Polytechnique, Paris.