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Project Reports

• Mars Analog Studies: Reflectance Spectroscopy of Organics in Ancient Rocks and Meteorites

  Aside from laboratory analyses of meteorites and in situ measurements by mass spectrometers on rover and lander platforms, the search for extraterrestrial organic material on Mars, carbonaceous© chondrite parent bodies, and other planetary surfaces is primarily limited to remote sensing techniques. Our team has been exploring the use of visible and near-infrared reflectance spectros-copy for assessing the presence and abundance of organic materials preserved in ancient terrestrial rocks and C chondrite meteorites. We have continued a series of controlled laboratory experiments to analyze (1) a suite of isolated kerogens and ancient terrestrial sedimentary rocks from various depositional environments and (2) several suites of synthetic clay-organic mixtures. Our goal is to better characterize the potential of reflectance spectroscopy as a method for organic detection and quantification in planetary environments, with the benefits that this technique is rapid, non-destructive, and applicable at laboratory, rover and orbital scales. The spectral models we are de-veloping will provide a foundation for quantifying organics that may be observed in spectroscopic data returned by the Hayabusa2 and OSIRIS-REx missions, laboratory spectra of C chondrites, and future Mars missions equipped with imaging spectrometers.

  ROADMAP OBJECTIVES: 2.1 4.1 4.3 6.1

• Mars Analog Studies: Mineral Assemblages in Terrestrial Settings

  It is now widely recognized that hydrated minerals, including clays, sulfates, chlorides and other salts, are important components of the martian crust. Such minerals and assemblages of minerals have the potential to record important information about past interactions between sediment, surface and groundwaters, and the atmosphere. The overarching theme of this project is to examine terrestrial analog sites to better understand how martian mineral assemblages may be used to infer these processes. Current sites include Rio Tinto, Spain and Lake Towuti, Indonesia. We have studied samples from the former and have determined that it may provide an appropriate mineralogical analog for enigmatic hydrous mineral-bearing terrains observed in Valles Marineris, Mars by orbiting spacecraft. Over the past year we have also begun to study mafic and ultramafic sediments in Lake Towuti to examine stratigraphic variations in Fe and Si-bearing mineral phases. Current results indicate these sediments and this lake system may be an appropriate mineralogical and/or chemical analog for ancient lacustrine sediments observed by the Curiosity rover in Gale Crater.

  ROADMAP OBJECTIVES: 2.1 4.1 4.3 6.1

• Astronomical Biosignatures, False Positives for Life, and Implications for Future Space Telescopes

  In this task, we identify novel biosignatures and also identify “false positives” for life, which are ways for non-biological processes to mimic proposed biosignatures. Of primary concern are false positives that could mimic easier to detect biosignatures like O₂, which we plan to search for with future space-based telescopes. This is a growing area of research that VPL’s past work has motivated, leading to multiple research teams across the planet following our example. Our work continues to be at the forefront of this area of work, as we have identified new non-biological mechanisms for mimicking signs of life. Further, we explained the ways in which these non-biological mechanisms could be identified, and “true positives” from biology confirmed with secondary measurements. Finally, we communicated these lessons to various teams that are studying concepts for future missions that would search for these signs of life. This connection to missions will ensure that our research is incorporated into those missions, so that they will not be “tricked” by these false positives.

  ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.3 5.2 5.3 7.2

• Biosphere-Geosphere Stability and the Evolution of Complex Life

  Five times in the past 500 million years, mass extinctions have resulted in the loss of greater than three-fourths of living species. Each of these events is associated with a significant perturbation of Earth’s carbon cycle. But there are also many such environmental events in the geologic record that are not associated with mass extinctions. What makes them different? We hypothesize that mass extinctions are associated with an instability in the carbon cycle. This project attempts to specify, both theoretically and empirically,the conditions that result in such an instability.

  ROADMAP OBJECTIVES: 4.3 5.1 5.2 6.1

• Habitable Planet Formation and Orbital Dynamical Effects on Planetary Habitability

  This task explores how habitable planets form and how their orbits evolve with time. Terrestrial planet formation involves colliding rocks in a thin gaseous disk surrounding a newborn star and VPL’s modeling efforts simulate the orbital and collisional evolution of a few to millions of small bodies to determine the composition, mass, and orbital parameters of planets that ultimately reach the habitable zone. After formation, gravitational interactions with the star and planet can induce short- and long-term changes in orbital properties that can change amount of energy available for the climate and to illuminate the planetary surface. The VPL simulates these effects in known and hypothetical planetary systems in order to determine the range of variations that permit planetary habitability.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 4.3

• Fullerenes and Mass Extinctions?

  A re-examination of past reports of the occurrence of fullerenes at mass extinction horizons, using proven extraction and analysis approaches, has failed to detect them. We conclude that fullerene cannot be used as a proxy for bolide impacts or mass extinction events.

  ROADMAP OBJECTIVES: 4.2 4.3

• Project 3F: Searching for Ancient Impact Events Through Detrital Shocked Zircons

  Understanding how quickly planetary surface environments evolve on newly accreted worlds is critical for predicting when habitable conditions are established. The meteorite impact history of the inner solar system strongly indicates that the Earth was subject to a global impact bombardment during the first few hundred million years after accretion. The scope, timing, and consequences of this profound process are hotly debated. This project investigated populations of detrital zircons in Archean sedimentary rocks to search for tell-tale signs of impact processes in the form of shock-induced microstructures that are diagnostic of impact. Such features have been shown to survive in detrital shocked zircons eroded from known impact structures on Earth, including the Vredefort, Sudbury, and Santa Fe craters. We have investigated populations of 1,000 zircons per sample using backscattered electron imaging of grain exteriors with a scanning electron microscope. Thus far we have surveyed zircons separated from rocks collected from the Yilgarn craton (Australia), North China craton (China), Wyoming craton (USA), the Superior craton (Canada). While intriguing microstructures have been observed, thus far no confirmed shock microstructures have been encountered in our Archean sample suites. Our inability the identify shocked grains in populations of 1,000 zircons (per sample) does not necessarily mean shocked grains are absent; our results provide constraints that if they are present, they are in abundances of <0.1% in the detrital population of the rocks investigated. We are currently in the process of more in-depth surveying (e.g., >1000 grains/sample) to test for very low frequency occurrency events. Our detailed search continues…

  ROADMAP OBJECTIVES: 1.1 4.1 4.3

• Project 4B: New Standards for Analysis of O and C Isotope Ratios in Ca-Mg-Fe Carbonates

  Stable isotope ratios are a powerful tool for determining the temperature and fluid conditions during formation of carbonates that host evidence for early life on Earth. However, sedimentary carbonates are often zoned at μm-scale and conventional analysis yields average values. We developed a suite of standards for the dolomite-ankerite series that allow us to make the first accurate SIMS (Secondary ion mass spectrometry) analyses oxygen and carbon isotope ratios at 1-10 μm-scale for these important carbonate minerals.

  ROADMAP OBJECTIVES: 1.1 4.1 4.3 7.1

• Early Animals: The Genomic Origins of Morphological Complexity

  Understanding the origins of life’s complexity here on Earth is paramount to finding it else-where in the universe. The fossil record indicates that complexity on Earth arose in a near geological moment – the famous Cambrian explosion – about 525 million years ago. However, molecular sequence analyses indicate that complex animals actually arose nearly 200 million years before they make their first appearance in the fossil record. This disparity between the advent of morphological complexity and its appearance in the fossil record motivates an interesting question – why is it that we cannot detect complex life here on Earth for nearly 200 million years? And if we cannot detect it on Earth, what hope would we have on an-other distant Earth-like planet? Our research is focused on addressing this question by trying to obtain a better understanding of what encodes morphological complexity in the genome. Our research suggests that a group of non-coding RNA genes – microRNAs – might be instrumental for the advent and maintenance of complexity in animals, and therefore sequencing the genomes and the transcriptomes (the ex-pressed component of the genome) from carefully chosen taxa might allow us to better under-stand the biology of animals that predated the Cambrian explosion.

  ROADMAP OBJECTIVES: 4.2 4.3