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tokens: and UV-illuminated (afterwards) gas condensation of the massive star-forming cluster that formed the Solar system. In this condensation, after a sudden decrease of the temperature due an increase in density and efficient dust cooling, PO condensed on grains along with other molecules, including complex species also detected in the comet (Goesmann et al. 2015 ; Altwegg et al. 2017b ). Under these physical conditions, deuteration increased, producing heavy water and other deuterated species detected in the comet (Altwegg et al. 2017a ). PO does not react easily with atomic H, which is the only mobile species on the dust grains at low temperature. This allowed a relatively high abundance of PO in the ices of the comet. 4.2.2 From Solar system bodies to primitive Earth: providing prebiotic P The confirmation of the presence of PO in the comet 67P/C–G has important implications for the prebiotic chemistry that occurred on the early Earth. The possible contribution of prebiotic material from comets is a long-standing topic (e.g. Chyba et al. 1990 ). Recent works have pointed out that comets could have contributed significantly to the chemical reservoir of our planet. O’Brien et al. ( 2018 ) claimed that of Earth’s water could have its origin in a cometary source, while Marty et al. ( 2017 ), based on ROSINA measurements of Xenon isotopes in 67P/C–G, showed that comets might have provided the of the Earth’s atmospheric Xe. In sight of our findings of P in 67P/C–G, we explore here the possible contribution of comets to the P reservoir on the early Earth. The amount of P in the Earth crust is 930 ppm (Yaroshevsky 2006 ), which means ∼2.6 × 10 22 g. However, most of this P is not available for biological processes, being locked in insoluble minerals. In the astrobiology community, there is an intense debate (known as the ‘phosphate problem’, see e.g. Menor-Salvan 2018 ) about the availability of inorganic phosphate at the dawn of our planet. Orthophosphate (PO), which is the most common form of P on Earth, is mainly found in apatite minerals. The insolubility of these minerals locks P, which is not available for (pre)biotic chemistry. To solve this scarcity of P, alternative sources of P should be explored. One possibility comes from meteorites. It has been measured that CI chondrites, a type of stony meteorites, contain a nearly solar P abundance (Lodders 2003 ). This suggests that an important fraction of P likely came to the Earth in rocks. However, as mentioned before, most of this P is not easily accessible to trigger prebiotic chemistry due to low solubility in water. As a possible solution, Pasek ( 2008 ) proposed that schreibersite, (Fe,Ni) 3 P, the major carrier of P in iron meteorites, which is more soluble in water, may be the main contributor of P in the early Earth. These authors claimed that that impacts of meteorites probably delivered between 10 18 and 10 21 g of P. Another extraterrestrial possibility would be the contribution from