Beyond The Lab: Introduction to Sample Science & In Situ Instruments

Overview

Sample science plays a pivotal role in advancing our understanding of the universe, and recent technological advancements have revolutionized the field. This article explores the importance of sample science, the impact of new technology on sample analysis, and the significance of studying samples from the moon, meteorites, and asteroids. Sample science holds immense value due to its ability to provide direct evidence and detailed insights into the composition, origin, and history of celestial bodies. By analyzing samples on Earth, scientists can employ a wide range of sophisticated laboratory techniques that are currently unavailable in space. These analyses allow researchers to determine elemental and isotopic composition, ages of rocks, and even search for potential signs of life.

New technologies are rapidly transforming sample science, enabling more precise and comprehensive analyses. While autonomous deep-space robots continue to evolve, limitations persist in terms of instrument size, robustness, and power requirements for spaceflight. However, advancements in miniaturization, durability, and power efficiency are gradually overcoming these barriers. As technology progresses, space-based instruments will become increasingly capable of performing a wider range of laboratory analyses, reducing the need for sample return missions.

Moon, Asteroid and IDP Samples

The Apollo missions, specifically Apollo 11 to 17, brought back a wealth of moon rock and regolith samples that have provided numerous scientific discoveries. One significant finding was the confirmation of the moon's volcanic history. Analysis of the lunar samples revealed the presence of volcanic basalts, which provided direct evidence of past volcanic activity on the moon. This discovery helped scientists understand the moon's geological evolution and the processes that shaped its surface. In addition, the samples provided valuable insights into the moon's age and the history of the solar system. Radiometric dating techniques revealed that the moon is approximately 4.5 billion years old, consistent with the estimated age of the solar system. This finding not only supported the prevailing theory of the moon's origin through a giant impact but also helped refine our understanding of the timing and sequence of events in the early solar system.

Despite possessing 382 kilograms of lunar material from the Apollo missions, these samples are limited to specific regions of the Moon. Obtaining samples from a broader range of locations is crucial to understanding lunar chronology. For instance, China's Chang'e-5 mission aims to collect samples from Oceanus Procellarum, which contains some of the youngest volcanic rocks on the Moon. These samples will help establish the timing of similar events on other celestial bodies, including Mercury, Earth, and Mars, enhancing our knowledge of the impact history of the inner solar system.

The Stardust mission, launched by NASA, aimed to collect samples from the coma of comet Wild 2 and interstellar dust. The spacecraft returned to Earth in 2006 with a full sample canister. The analysis of these particles revealed that the comet material contained a wide variety of organic compounds, including glycine, an amino acid that is a building block of life. This finding suggests that comets may be viable as future targets for sample missions that seek to discover biomolecules. Additionally, the mission discovered mineral grains that were formed under high-temperature conditions. These grains are known as calcium-aluminum-rich inclusions (CAIs) and are typically found in primitive chondrites. The presence of CAIs in cometary material means that comets like Wild 2 contain material which formed close to the young Sun, providing insights into the early stages of the solar system's formation.

The Hayabusa2 mission, conducted by the Japan Aerospace Exploration Agency (JAXA), successfully collected samples from the asteroid Ryugu and returned them to Earth in December 2020. One of the key findings from the Hayabusa2 samples is the presence of organic compounds on the asteroid Ryugu. The analysis revealed the presence of various organic molecules, including water and amino acids. This discovery is crucial because it suggests that asteroids like Ryugu may have contributed to the delivery of organic compounds to Earth, potentially playing a role in the origins of life.

The samples also revealed that the asteroid's surface is composed of both fine-grained particles and larger rocky fragments. The presence of these fragments indicates that Ryugu underwent significant impact processes in its history. Additionally, evidence of solar wind bombardment was observed, similar to the Hayabusa findings on Itokawa. These findings contribute to our understanding of the dynamics and evolution of asteroids in the solar system.

The OSIRIS-REx mission, led by NASA, aimed to collect samples from the asteroid Bennu. The spacecraft reached Bennu in 2018 and successfully retrieved a sample in 2020. The samples are estimated to return on September 24th of this year, but some preliminary findings have already been reported such as general mineral composition. OSIRIS-REx is a fantastic example of a few technological advancements being made. Among the many tools on board, two of the most important are the Visible and Infrared Spectrometer (OVIRS) and Touch-And-Go Sample Acquisition Mechanism (TAGSAM). The OVIRS measures the reflectance of light across different wavelengths, providing valuable information about the mineral composition of the Bennu samples. TAGSAM is responsible for retrieving the samples via a burst of pure nitrogen gas that pushes surface regolith into the sampler’s chamber.

By utilizing the onboard instruments, scientists discovered prior to sample return that the asteroid's surface is covered in a diverse range of carbon-rich organic molecules, including amino acids. This suggests that asteroids like Bennu may have played a role in delivering organic compounds to Earth, potentially contributing to the origin of life. The preliminary sample return data also provided valuable information on the asteroid's physical properties, such as its geologic history and surface roughness, improving our understanding of asteroid dynamics.

Advancements of In Situ Instruments

Miniaturized analytical instruments have revolutionized the field by enabling on-site analyses with improved sensitivity and precision. The X-ray Fluorescence (XRF) Spectrometer is commonly used for elemental analysis of samples. The latest miniaturized version is the Mars Hand Lens Imager (MAHLI) designed for NASA's Mars rover missions. It operates by irradiating the sample with X-rays which then interact with the atoms in the sample causing the atoms to emit characteristic fluorescent X-rays. The energy and intensity of the emitted X-rays can then be analyzed to determine the elemental composition of the sample. MAHLI has been instrumental in identifying the mineralogy and elemental composition of Martian rocks and soils. It has provided key insights into the geological history and environmental conditions of Mars, such as detecting the presence of clay minerals that indicate past water activity. MAHLI's miniaturization allows for in situ analysis of samples, reducing the need for sample return missions and enabling real-time scientific discoveries on the Martian surface.

A Raman Laser Spectrometer (RLS) was miniaturized and implemented into the design of the European Space Agency's ExoMars rover. The RLS works by illuminating the sample with a laser, and the scattered light is analyzed to determine the vibrational modes of the sample's molecules, providing information about its chemical composition. In contrast to XRF, RLS provides details about the molecular bonds, crystal structures, and functional groups present in the sample. It is also particularly useful for identifying complex organic compounds and detecting subtle variations in molecular structure. The ExoMars mission aims to search for signs of past or present life on Mars. By studying the composition of Martian samples in situ, RLS contributes to our understanding of Mars' habitability and the potential for past or present life on the planet.

Finally, the star of the show as far as this article is concerned, is the Scanning Electron Microscope (SEM). Yes you read that right, this is not a joke, NASA is actually miniaturizing an SEM. Most SEMs, such as those used in a university laboratory, are typically the size of a medium-to-large desk. The SEM is a powerful instrument that uses a focused beam of electrons to image the surface of samples with high resolution and provide precisely targeted composition analysis. The miniaturized version of the SEM, known as the Scanning Electron Microscope for Europa (SEMUE), is under development by NASA to study samples from icy moons. Research into the miniaturization of an SEM for use onboard a rover or lander began at NASA back in 2010 with the publication of an initial research statement titled, “Miniaturized Environmental Scanning Electron Microscope for In Situ Planetary Studies”.

This overview of the initial engineering plans discusses the design of a Field Emission Electron Gun, that is sized at a bewildering <8”x4”x4”. For reference, the smallest SEM available on the public market in 2023 is 16”x12”x16” and it’s widely considered to be rather unreliable. Thus, not only is NASA constructing an engineering feat purely through miniaturization, but also proposed functionality. The 2010 publication concluded with the successful fabrication and test of the electron-focusing column, successful focus image capture and subsequent regulation of the desired beam current using a high-voltage power supply system. It then goes on to state that future fabrication and testing includes the mating of the column/scanning system with the gun assembly for further characterization.

Since this initial publication no details have been released other than the name, SEMUE, which was announced late last year. The SEMUE will enable detailed studies of the surface morphology, mineralogy, and elemental composition of icy samples from Europa. Once deployed, SEMUE will contribute to our understanding of the potential habitability of Europa's subsurface ocean and the nature of its icy shell. It will help identify regions where the conditions may be suitable for life and aid in the selection of future landing sites for missions to explore this intriguing moon.

Conclusion

By analyzing samples from celestial bodies scientists can search for organic molecules, isotopic signatures, and potential biomarkers. Analyzing the chemical composition and structures of these samples provides insights into the conditions necessary for the emergence of life and the distribution of life-building blocks throughout the universe. Sample science will soon be on the forefront of assessing the habitability potential of other celestial bodies. In the not so distant future, the study of samples from Mars' ancient lake beds will allow us to evaluate the presence of key elements, minerals, and energy sources that could support life.

The integration of sample science into the study of astrobiology has played a crucial role in unraveling the mysteries of life beyond Earth. The specific advancements in miniaturized analytical instruments and advanced microscopy techniques have significantly expanded our understanding. As technology continues to advance and sample science further evolves, we can anticipate groundbreaking discoveries and deeper insights into the cosmos that will shape our understanding of the universe and our place within it.

References

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Qu, H., Ling, Z., Qi, X., Xin, Y., Liu, C., & Cao, H. (2021). A Remote Raman system and its applications for planetary material studies. Sensors, 21(21), 6973. https://doi.org/10.3390/s21216973

Tulej, M., Iakovleva, M., Leya, I., & Wurz, P. (2010). A miniature mass analyser for in-situ elemental analysis of planetary material–performance studies. Analytical and Bioanalytical Chemistry, 399(6), 2185–2200. https://doi.org/10.1007/s00216-010-4411-3

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