JpGU-AGU Joint Meeting 2020

Presentation information

[J] Oral

B (Biogeosciences ) » B-BG Biogeosciences & Geosphere-Biosphere Interactions

[B-BG02] Interaction between Life, Water, Mineral, and Atmosphere

convener:Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yohey Suzuki(Graduate School of Science, The University of Tokyo)

[BBG02-01] Search for biosignatures on Mars by the Life-signature Detection Microscope (LDM)

*Yoshitaka Yoshimura1, Akihiko Yamagishi2, Atsuo Miyakawa2, Satoshi Sasaki3, Eiichi Imai4, Keigo Enya5, Kensei Kobayashi6, Yoko Kebukawa6, Tomoka Okada6, MITA Hajime7, Takeshi Naganuma8, Takehiko Satoh5, Kazuhisa Fujita5, Tomohiro Usui5 (1.Tamagawa University, 2.Tokyo University of Pharmacy and Life Science, 3.Tokyo University of Technology, 4.Nagaoka University of Technology, 5.Japan Aerospace Exploration Agency, 6.Yokohama National University, 7.Fukuoka Institute of Technology, 8.Hiroshima University)

Keywords:Fluorescent microscope, Astrobiology

Present Mars is hostile to life, but recent findings tend to support the possible presence of microbes near the Mars surface. MSL Curiosity has found organic compounds [1], the temporal increase of methane concentration in the Martian atmosphere [2], and reduced sulfur compounds such as pyrite in Martian soil [3]. Methane and reduced sulfur compounds can be energy sources to support the growth of chemoautotrophic microbes [4]. The detection of hydrated salts at Recurring Slope Lineae suggested the possible presence of liquid water [5]. Since UV radiation, which is harmful to life, would be shielded by thin layers (less than a millimeter) of dust or regolith [6], microbes could survive under a depth of several centimeters from the surface. Although the Viking mission in the 1970s did not find evidence for life on the Mars surface [7], the sensitivity of the GC-MS (mass spectrometer) was found not to be very high. It was not able to detect 106 microbial cells in 1-gram soil [8, 9], indicating that another life detection program is necessary.

The Life-signature Detection Microscope (LDM), which we have proposed [10], has the potential sensitivity much higher than the Viking instrument. The LDM is based on fluorescent microscopy and detects organic compounds, membrane structures, and catalytic activities stained by fluorescent pigments. This technique is especially useful for the detection of living microbes. It has the potential to detect a single cell and visualizes their shapes, sizes, and other morphological structures at a spatial resolution of 1 µm. The sensitivity can also be as high as desired just by increasing the volume of the sample to be scanned in a reasonable duration of experiments. LDM scans about 1 mm3 and detects less than 104 cells in 1 gram soil, which is comparable to the least populated area of the terrestrial environment on Earth, such as the Atacama desert in Chile. If microbes are not detected, we can determine the upper limit of the microbial density, which is useful information to evaluate the risk of human contact with Martian microbes in future manned explorations.

Currently, we have been developing the breadboard model (BBM) of LDM. We will report the current status of the BBM and discuss how and where to find biosignatures on Mars.


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[10] Yamagishi, A., et al., Trans. JSASS, Aerospace Technology Japan, 16 (2018) 299-305.