Immiscible basaltic glasses – a prebiotic phosphate source

Phosphorus is an essential element of life, as observable in modern life forms that have perfected phosphorus accumulation and recycling. Prebiotic chemistry, on the other hand, was likely challenged by the low abundance and poor solubility of phosphorus minerals on early Earth.

Current experimental approaches to solve this so-called phosphate problem mainly focus on the solubilization of phosphate minerals like apatite or reduced phosphorus species in extraterrestrial schreibersite. However, the possibilities for prebiotic chemistry through magmatic evolution and phosphate enrichment in basaltic melts have not yet been considered.

Here, we show the formation of phosphate-rich glass droplets, driven by liquid immiscibility in basaltic melts, and explore its downstream utilization for prebiotic chemistry. We synthesized two glasses mimicking an average composition of 2.2 – 3.8 Ga old basalts containing more than 0.5 wt.% phosphorus, and doped them with 1 and 10 wt.% P₂O₅ respectively. In the latter, unmixing lead to the formation of Fe-P-rich droplets in a Si-rich matrix with a partition coefficient of D_P ~3.9. Subsequent leaching behavior of the synthesized glass was investigated over a range in pH and organic solvents delivering up to 5 mM dissolved phosphate. The concentration in the experimental leachate was sufficient to form di- and triphosphate afterwards at elevated temperatures and phosphorylation of adenosine was possible.

We further found that our initially produced leachates were able to trigger the synthesis of imidazole phosphate with up to 34 % yield and the downstream phosphorylation of glycerol in wet/dry cycles with up to 17 % yield. Our results thus show an alternative source of phosphate for prebiotic chemistry through its early enrichment in the magma and present an alternative approach to solving the phosphate problem for the origin of life.