22-EPN3-092: Deciphering Traces of Life from the Dawn of Earth’s Biosphere
April 26, 2024

22-EPN3-092: Deciphering Traces of Life from the Dawn of Earth’s Biosphere

Visit by Nisha Ramkissooon (The Open University, UK) to TA2.2 VU (Exo)Planetary Interior Simulation Laboratory (PISL).
Dates of visit: 12-16 February 2024

Report Summary: In the search for evidence of ancient terrestrial life there are some obstacles. Purported biosignatures have been identified in a range of ancient mineral deposits, including silica. However, some of these signatures can also be generated under abiotic conditions, which brings into question their biological origin. In addition, the oldest fragments of the Earth’s crust are at least 3.8 Gyr, and would have experienced significant metamorphic alteration since their formation. Therefore, any preserved biosignatures could have also undergone extensive modification during metamorphism potentially making some of them unidentifiable. This project aimed to examine the effect of metamorphism on the modification of biosignatures preserved in silica deposits. 

Silica sinters were synthetically created in the laboratory via evaporation in the presence and absence of microbes. These samples were then exposed to simultaneous high temperature and high pressure conditions using the end-loaded piston-cylinder at the (Exo) Planetary Interior Simulation Laboratory (PISL), VU University, Amsterdam. Samples were individually subjected to pressures and temperatures of 650 °C and 12 kbar, respectively, for 20 hours. Raman spectroscopy and GC-MS will be used to assess changes in mineralogy and to quantify changes to organic molecules. Initial results obtained after returning to my home institution show that the high pressure and high temperature conditions experienced in these experiments led to changes in the crystalline structure of the samples. This resulted in samples transforming from silica glass to quartz.