Free Astronomy Magazine November-December 2016

of deuterium that is three times higher that of terres- trial waters. This suggests that all comets must have formed in a much cooler re- gion of the protosolar neb- ula, and thus decidedly farther from the Sun than the one in which our planet formed. However, it remains valid the assumption that comets brought to Earth some of the building blocks of life. In fact, both Roset- ta from orbit and Philae on the surface have identified a number of organic com- pounds that can be crucial for the onset of life in a hos- pitable environment like our planet. For example, it has been detected the presence of glycine, an amino acid found in some proteins (such as hemoglobin) which is 67 P/Churyu- mov-Gera- simenko shot on 29 September from two differ- ent angles with the OSIRIS cam- era, when Rosetta was less than 23 km away from the centre of the comet. The im- age scale is 2.2 metres/pixel. [ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IA A/SSO/INTA/UPM/ DASP/IDA]