Hypervelocity impacts of DNA on soft metals and implication for sample capture and characterisation efficiency

DNA is ubiquitous to all life on Earth and is thus considered an indicator for a universal ancestor; however, the origin of this ancestor is debated. Possible origins include endogenous production, for example in the young Earth’s oceans around hydrothermal vents, or exogenous delivery, as a result of impacts early in the Earth’s history [1]. If the former is correct, then Enceladus, with its briny liquid ocean, high geologic activity resulting in hydrothermal vents at the ocean-core boundary, and high abundance of complex organic molecules and fragments, is one of the key astrobiological targets within our Solar System [e.g., 2, 3]. However, its thick icy surface means it is not feasible for us to directly access and sample the ocean [4]; but conveniently, large plumes of ice and vapour are found to erupt from the Enceladean South Polar Region, potentially carrying a whole wealth of knowledge about the subsurface ocean [5]. As a universal feature of biological life on Earth, the detection of DNA in the ocean of Enceladus would provide strong indications of life within.

One of the biggest challenges for sample collection and analysis from the Enceladean plumes is capture speed, and thus peak impact shock pressure, which depend on the orbit type and is expected to range from 250 m/s (Enceladus orbit), up to 6 km/s or more (Saturn orbit/Enceladus flyby) [5]. Careful planning is therefore required to ensure efficient sample capture with minimal disruption or modification to minerals, organics, and biomarkers. Using the Light Gas Gun at the University of Kent, we are investigating the effect of impacts on the structure of DNA using a range of collection mediums, as well as different methods of post-impact recovery and analysis. At low speeds, up to ~ 1 km/s, short DNA ladders up to 1000 bp can survive and be characterised in analysis after impacting a soft metal such as indium. However, at higher speeds the concentration and structure of the DNA is lost. By contrast, DNA impacted onto aluminium is able to withstand speeds up to ~2.5 km/s, although there are potential signs of ladder breakdown. Further work at higher speeds is on-going to provide more definitive breakdown characterisation. Nevertheless, these preliminary results indicate that it would indeed be possible to successfully collect and characterise any small-chain DNA present in the plumes of Enceladus within current mission proposal constraints which include Enceladean orbiters. 

[1] Chyba & Sagan, 1992, Nature; [2] Postberg et al., 2018, Nature; [3] Khawaja et al., 2025, Nature Astronomy; [4] Hemingway & Mittal, 2019, Icarus; [5] Burchell & Wozniakiewicz, 2024, MAPS.