Towards Determining Biosignature Retention in Icy World Plumes

• Main Authors: Kathryn Bywaters, Carol R. Stoker, Nelio Batista Do Nascimento, Lawrence Lemke
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: Life
• Subjects: icy world; plume; life detection; microbes; lipids; Europa
• Online Access: https://www.mdpi.com/2075-1729/10/4/40

With the discovery of the persistent jets of water being ejected to space from Enceladus, an understanding of the effect of the space environment on potential organisms and biosignatures in them is necessary for planning life detection missions. We experimentally determine the survivability of microbial cells in liquid medium when ejected into vacuum. Epifluorescence microscopy, using a lipid stain, and SEM imaging were used to interrogate the cellular integrity of <i>E. coli</i> after ejected through a pressurized nozzle into a vacuum chamber. The experimental samples showed a 94% decrease in visible intact <i>E. coli</i> cells but showed a fluorescence residue in the shape of the sublimated droplets that indicated the presence of lipids. The differences in the experimental conditions versus those expected on Enceladus should not change the analog value because the process a sample would undergo when ejected into space was representative. <i>E. coli</i> was selected for testing although other cell types could vary physiologically which would affect their response to a vacuum environment. More testing is needed to determine the dynamic range in concentration of cells expected to survive the plume environment. However, these results suggest that lipids may be directly detectable evidence of life in icy world plumes.