Strategy for Detection of Extant Life on Mars by Measuring Enzymatic Activities

Abstract

A number of Mars missions have been operated, and it is suggested that plenty of water was present on the surface of Mars. Now the aim of missions is moved from "follow the water" to "follow the carbon". Many methods to detect extant and/or extinct life have been proposed, but there is no comprehensive one since we do not know the nature of Martian life if any. We proposed the methods based on the detection of enzymatic activity: Fluorescence microscopy methods with esterase substrates, and butch methods with phosphatase substrates. When CFDA-AM (substrate which gives fluorescence after hydrolyzed) was used, most of terrestrial microorganisms could be detected, while only 1 % of them could be detected by using the cultivation method. By using p-nitrophenyl phosphate or 4-methylumbelliferyl phosphate, we could detect microbial activities in such terrestrial extreme environments as core samples of submarine hydrothermal sub-vents, chimneys of submarine hydrothermal vents, and surface soils in Antarctica. It is promising to detect extraterrestrial extant life by using these enzymatic detection methods, combined with other chemical methods such as analysis of D/L ratios of amino acids.