Chemical and Optical Identification of Micrometer-Sized 1.9 Billion-Year-Old Fossils by Combining a Miniature Laser Ablation Ionization Mass Spectrometry System with an Optical Microscope

Abstract

The recognition of biosignatures on planetary bodies requires the analysis of the putative microfossil with a set of complementary analytical techniques. This includes localized elemental and isotopic analysis of both, the putative microfossil and its surrounding host matrix. If the analysis can be performed with spatial resolution at the micrometer level and ppm detection sensitivities, valuable information on the (bio)chemical and physical processes that influenced the sample material can be gained. Our miniaturized laser ablation ionization mass spectrometry (LIMS)-time-of-flight mass spectrometer instrument is a valid candidate for performing the required chemical analysis in situ. However, up until now it was limited by the spatial accuracy of the sampling. In this contribution, we introduce a newly developed microscope system with micrometer accuracy for Ultra High Vacuum application, which allows a significant increase in the measurement capabilities of our miniature LIMS system. The new enhancement allows identification and efficient and accurate sampling of features of micrometer-sized fossils in a host matrix. The performance of our system is demonstrated by the identification and chemical analysis of signatures of micrometer-sized fossil structures in the 1.9 billion-year-old Gunflint chert.

Morphological Biosignatures in Volcanic Rocks – Applications for Life Detection on Mars

“…Miniaturized laser ablation ionization mass spectrometry (LIMS)-time-of-flight mass spectrometer for space missions capable of performing in situ isotope measurements of minerals at planet surfaces in vacuum have been developed and tested, but not included, in the payloads of ExoMars or NASAs mars mission 2020 (Wiesendanger et al, 2018). Isotope measurement thus have to be targeted for the subsequent Mars sample return mission.…”

Novel 2D binning approach for advanced LIMS depth profiling analysis

“…Recently, a high-resolution microscope camera system with imaging resolution of about 1 mm designed for ultra-high vacuum conditions was integrated in the current LIMS setup to allow accurate targeting of the desired positions on the sample. 26 The microscope camera system is positioned next to the mass spectrometer, parallel to the ion optical axis of the mass spectrometer, which is about 70 mm away. A single laser ablation crater on the sample surface can be used for the calibration of the translation distance between the microscope and mass spectrometer (reproducibility of the position is 2.7 AE 1.2 mm).…”

A method for improvement of mass resolution and isotope accuracy for laser ablation time‐of‐flight mass spectrometers

“…The measurements are conducted with our miniature laser mass spectrometer (LMS) composed of a grid‐less reflectron‐type TOF mass spectrometer and a femtosecond laser‐ablation ion source and are described in full detail in our previous publications . In this contribution, we only give a short overview of the system.…”

“…These data can be used to determine times of formation of the planetary solids and provide insights into geological processes shaping planetary surface . The mass spectrometric analyses can be also of primary importance in detection of bio‐signatures …”

“…Two 8‐bit two‐channel ADC cards with a sampling speed of 4 GS/s are used to acquire the spectra. A custom‐made microscope next to the mass spectrometer allows to locate and sample features of interest in heterogeneous samples with μm accuracy . The data analysis is performed using our in‐house software that uses the Simpson method for peak area determination.…”