Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023-2032 (2022)

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F Glossary and Acronyms -A- AAAC: Astronomy and Astrophysics Advisory Committee. Abiosignature: A substance that mimics a biosignature, but is not associated with life. Abiotic: Of or relating to nonliving things; independent of life or living organisms. Accretion: The growth of a massive object by gravitationally attracting more matter, typically gaseous matter, in an orbiting accretion disk, causing the object to grow larger, hotter and more luminous. A related term is used in meteorology for the process of accumulation of frozen water as precipitation over time as it descends through the atmosphere: i.e., the basis of cloud formation. ADAPT: Adaptable, Deployable Entry Placement Technology Additive manufacturing: Set of manufacturing technique based on adding layer-upon-layer material. The most well-known of such method is 3D printing. Aero-assist maneuver: Use of a body’s atmosphere to modify the trajectory of a spacecraft. Aerocapture is an example of such maneuver. Aerocapture: Deliberate use of a aerodynamic drag in an atmosphere to facilitate orbital capture of a spacecraft without the use of thrusters. Albedo: The fraction of light that is reflected from the surface of a planetary body. ALHAT: Autonomous Landing Hazard Avoidance Technology. Safe landing technology development program, predecesor to SPLICE. ALICE: An ultraviolet imaging spectrometer that has flown on several spacecraft including NASA’s New Horizons Pluto flyby and ESA’s Rosetta comet rendezvous mission. AO: Announcement of Opportunity. Archean: The second geologic eon on Earth, occurring after the Hadean and lasting from 4 billion to 2.5 billion years ago ARMD: Aeronautics Research Mission Directorate. Artemis: NASA’s current program to return humans to the moon later this decade. AU: Astronomical Unit, the mean distance from the Earth to the Sun. Autotroph: An organism that utilizes inorganic sources as nutrition and energy sources. AVGR: NASA’s Ames Vertical Gun Range. Axel: Family of rover platforms developed at JPL, providing versatile mobility on planetary surfaces. -B- Biogenesis: The production of substances through biological processes. Biosignature: A sign that can be interpreted as evidence of life. Biosphere: the layer of a planet where life exists; the sum total of a planet’s ecological systems Biotic: Relating to life or living organisms. Bistatic: a radar technique where the transmitter and receiver are at different locations. Bolide: An extremely bright meteor caused when a extraterrestrial body enters into and explodes in Earth’s atmosphere, explodes in Earth’s atmosphere. Portions of the body—meteorites— may survive to reach Earth’s surface. Bouguer gravity: A gravitational anomaly that requires the incorporation of terrain height for correction. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-1 

Breccias: A type of sedimentary rock that is comprised of various minerals bound in a matrix that holds them together. -C- CDR (Critical Design Review): During phase C, evaluation of full maturity of a mission or technology, that it is ready to complete design and fabrication. Channel coding: process of detecting and correcting bit errors in digital communication systems. Chemoautotropic: an organism, typically bacteria or archaea that can derive energy from chemical reactions involving inorganic molecules Chemolithoautotroph: A chemoautotropic organisms whose metabolism is supported via inorganic compounds derived from minerals. Chemosynthesis: Organic compounds created by living organisms through chemical means. Chirality: The right- or left-handedness of an asymmetric molecule. Chondrite: A stony meteorite, unaltered from its parent body Chondrule: Round grains that make up a fraction of chondrites, formed from molten or partially molten droplets of minerals. Circumstellar disk: A broad ring of material orbiting around a star. CISM: Center for Integrated Space Weather Modeling Clathrate: A chemical substance consisting of a lattice of one type of molecule (e.g., water) trapping and containing a second type of molecule (e.g., methane). Clathration: The chemical process leading to the formation of a clathrate. CLPS: Commercial Lunar Payload Services CML (Concept Maturity Level): Index of mission concept maturity ranging from 1 (rudimentary sketch) to 9 (critical design review stage). COLDTech: Concepts for Ocean worlds Life Detection Technology. CRISM: Compact Reconnaissance Imaging Spectrometer for Mars. Corona: The outermost layer of a star. Covalent bond: A chemical bond formed when atoms share electrons. Cryogenics: The branch of physics dealing with the behavior of matter at very low temperatures. Cryovolcanism: The eruption of water and other volatile materials onto the surface of a planet or moon due to internal heating. CSA: Canadian Space Agency Curiosity’s SAM: The Curiosity rovers Sample Analysis at Mars (SAM) instrument. -D- D/H ratio: Deuterium to hydrogen ratio DAPR: Dual anonymous peer review DART: Double Asteroid Redirection Test. Delta-V (ΔV): Impulse per unit of spacecraft mass (i.e., velocity change) that is needed to perform a given maneuver. Derivatization: Modifying a chemical compounds to give it properties more amenable to a particular analytical method. Diagenesis: the change of sedimentary rock during and after rock formation at temperatures and pressures less than what is required for the formation of metamorphic rocks but excludes surface alteration. Diagenetic: Any chemical or physical that will be affecting sedimentary substances as they solidify. Dilute Core: An extended region of enriched elements heavier than hydrogen or helium in the deep interior of the giant planets. DNA: Deoxyribonucleic acid. The genetic biopolymer found in most if not all organisms on Earth. Its helical structure is maintained by the presence of four nucleobases: adenine, guanine, cytosine, and thymine. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-2 

DOE: Department of Energy. Dragonfly: A NASA rotorcraft mission scheduled to be sent to Titan in the late 2020s. DTRA: Defense Threat Reduction Agency. Dynamo: An electromagnetic process in which the movement of conductive material gives rise to a magnetic field. -E- EA: Equity and accountability Eccentricity: A measurement of the degree to which an elliptical orbit deviates from a circular orbit. An ellipse of zero eccentricity is a circle. Electro-optical sensors: Electronic detectors that convert light, into an electronic signal. Electromagnetic sounding: Determination of variations in electrical conductivity with depth. Egalitarianism: The idea that all people deserve equal opportunities. EIL: NASA’s Johnson Space Center’s Experimental Impact Laboratory. EM: Electromagnetic. Emission spectrum: A spectrum composed solely or predominantly of emission lines, indicating the presence of hot gas and a nearby source of energy. Endogenic: Relating to a process of internal origin. Energy density: The amount of energy per volume. ESA: European Space Agency. ESSIO: Exploration Surface Strategy Integration Office. Europa Clipper: A large NASA multiflyby mission scheduled for launch to Europa in the mid 2020s. EVA: extravehicular activities. Exogenic: Relating to a process of external origin. Exoplanets: Planets formed around stars other than the Sun. Extremophile: A living organism that is capable of living in extreme physical or chemical conditions, including high or temperatures, high salinity, and intense radiation. -F- False-negative: Results that wrongly indicate negative results. False-positive: Results that wrongly indicate a positive result. Felsic: Igneous rocks enriched in lighter elements (e.g., silicon, oxygen, aluminum, sodium, and potassium) that form feldspar and quartz. Flux: A measure of the energy or number of particles passing through a given area of the surface in unit time. Flyby: Operation in which a spacecraft passes in close proximity to another body, but is not in orbit about it. Forward contamination: Contamination of extraterrestrial bodies with terrestrial life forms (see planetary protection). FPS: Fission power systems. -G- GBT: Green Bank Telescope. GCM: General Circulation Model. GEO: Geosynchronous Earth orbit. Geodetic: Relating to investigations of the shape of a planetary body. Geosphere: The solid layers of a planet, including its core. GNC: Guidance, Navigation, and Control. GPU: Graphical Processing Unit. Specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images. Graphene: Allotrope of carbon with desirable physical and electrical properties. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-3 

Gravity assist maneuver: Use of the relative movement and gravity of an astronomical object to alter the path and speed of a spacecraft, GRAIL: Gravity Recovery and Interior Laboratory. A NASA orbiter that investigated the Moon’s interior structure. GSFC: Goddard Space Flight Center. GSSR: NASA’s Goldstone Solar System Radar. Gyr/Gya/Ga: Gigayear, one billion years. -H- Habitability/Habitable: The ability of a planet to harbor life at some specific time but does not necessarily do so. Habitable Zone: The zone surrounding a star at which liquid water could exist on a planetary body with a sufficiently dense atmosphere. Hadean: The first geologic eon on Earth, lasting from the planet’s formation 4.540 billion years ago to 4 billion years ago. Hadley convection: A type of convective circulation pattern seen in planetary atmospheres. Hayabusa 2: The JAXA sample-return mission to asteroid Ryugu. HEET: Heatshield for Extreme Entry Environment Technology. HEOMD: Human Exploration and Operations Mission Directorate. HD&A: Hazard detection and avoidance. HIAD: Hypersonic Inflatable Aerodynamic Decelerator. HIHT: High Irradiance, High Temperature. HLS: Human Landing System. HOTTech: High Operating Temperature Technology, a NASA technology development program. HPC: High Performance Computing. Hydrocode: Complex computer simulations of dynamic fluid events such as the formation of an impact crater. Hydrosphere: All bodies of water on a planet, as distinguished from the lithosphere and the atmosphere. Hydrothermal: Relating to the action of hot liquid or gas within or on the surface of a planet. -I- IAA: International Academy of Astronautics. IAWN: International Asteroid Warning Network. IBD: Ion Beam Deflection. IMIM: International Mars Ice Mapper, a proposed radar mapping mission. Infrared spectroscopy: measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. Inorganic: Compounds not associated with life and/or not containing carbon. Interstellar medium: Space between the stars, made of gas (primarily helium and hydrogen). Ionosphere: The region of a planet’s atmosphere that is kept partially ionized by solar ultraviolet and X- ray irradiation. IRTF: NASA’s Infrared Telescope Facility. ISFM: Internal Scientist Funding Model. Isotope: One of two or more atoms of the same element that have the same number of protons in the nucleus but a different number of neutrons. Isotopic: Species of the same element that have different atomic weights. ISP: Specific impulse of a propulsion device. Measure of how efficiently a reaction mass engine creates thrust. ISRO: Indian Space Research Organisation. ISRU: In Situ Resource Utilization. ITAR: International Traffic in Arms Regulations. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-4 

-J- JWST: James Webb Space Telescope. A joint NASA-ESA space telescope currently awaiting launch. JAXA: Japan Aerospace Exploration Agency. Jovian: Pertaining to the planet Jupiter or a similar sized exoplanet. JPL: Jet Propulsion Laboratory. JUICE: Jupiter Icy moon Explorer. An ESA Ganymede orbiter mission scheduled for launch in the mid 2020s. -K- KBO: Kuiper belt object. KDP (Key Decision Point): Events at which the decision authority determines the readiness of a program/project to progress to the next phase of the life cycle. Keck: Keck Observatory. Kepler mission: NASA missions that serached for exoplanets using the transit technique. Kerogens: Naturally occurring insoluble matter found in sedimentary rock. Kuiper Belt: A region of the outer solar system containing icy planetesimals distributed in a roughly circular disk some 40 to 100 AU from the Sun. -L- LANL: Los Alamos National Laboratory. LCRD: Laser Communications Relay Demonstration. NASA mission to showcase the use of optical communication in space. LCRD: Laser Communications Relay Demonstration. LEO: Low Earth orbit. LIDAR: Light Detection and Ranging. LIHT: Low Irradiance, High Temperature. Lithology: The study of rocks’ physical characteristics and formation. Lithosphere: The outermost shell of a rocky planet. On Earth, the lithosphere is the crust and the relatively elastic portion of the upper mantle. LLNL: Lawrence Livermore National Laboratory. Lobate scarps: These are curvilinear structures found on the surfaces of some planetary bodies. LRO: Lunar Reconnaissance Orbiter. LRV: Lunar Roving Vehicle. LADEE: Lunar Atmosphere, Dust, and Environment Explorer. -M- M dwarf: Sometimes called “red dwarfs”, these stars are the smallest type on the main sequence. Macromolecule, Macromolecular: Of or pertaining to a molecule—e.g., a nucleic acid, protein, or synthetic polymer—containing a very large number of atoms. Magnetosphere: The region of space in which a planet’s magnetic field dominates that of the solar wind. Magnetotail: The portion of a planetary magnetosphere pulled downstream by the solar wind. Mantle: The part of a planet between its crust and core, composed of relatively dense materials. MEDLI: Mars Entry, Descent and Landing Instrument, used to monitor the performance of a spacecraft’s heatshield during atmospheric entry. MEDA: Mars Environmental Dynamics Analyzer. Instrement that makes weather measurements including wind speed and direction, temperature and humidity, and also measures the amount and size of dust particles in the martian atmosphere. MOXIE: Mars Oxygen In Situ Resource Utilization Experiment. An oxygen-producing ISRU experiment on the Perseverance rover. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-5 

Mars 2020: NASA’s Perseverance sample-collecting rover mission. Mascons: A large positive gravitational anomaly located on an area of a planetary body’s surface. Mass spectrometry: Analytical technique used to measure the mass-to-charge ratio of ions. MASWG: Mars Architecture Strategy Working Group. MatISSE: Maturation of Instruments for Solar System Exploration. NASA program that supports the development of spacecraft-based instruments, covering TRL-4 to TRL-6. MAVEN: Mars Atmosphere and Volatile Evolution Mission. MEMS: Micro-electromechanical systems. MEP: Mars Exploration Program. MESSENGER: NASA’s Mercury Surface, Space Environment, Geochemistry, and Ranging mission. Metabolism: A set of chemical reactions that change nutrients into the energy needed by a lining organism to maintain structure,grow and replicate. MMRTG: Multi-mission radioisotope thermoelectric generator converts the heat from the decay of radioactive plutonium-238 into electrical power. Monomer: A subunit of a polymer, when bonded to other identical subunits. MSFC: NASA’s Marshall Space Flight Center. MSR: Mars Sample Return Muon tomography: Use of cosmic ray muons to construct 3-dimensional models of the density distribution in an object. MWG: NEO Modeling Working Group. -N- NASA: National Aeronautics and Space Administration. NASA Standard Assay (NSA): Procedure to verify spacecraft cleanliness for missions with bioburden requirements. Nascent: Emerging and coming into existence. NASEM: National Academy of Sceince, Engineering, and Medicine. Nanomolar level: Measure of concentration of a given chemical component. N-body simulations: A computer simulation of a dynamic behavior of a system consisting of a large number of particles as they interact in response to gravitational and/or other forces. NCAR: National Center for Atmospheric Research. Nebula: A cloud of gas and dust in space. NED: Nuclear explosive devices. NEO: Near Earth Object. NEOSM: Near-Earth Object Surveyor mission. NEP: Nuclear-Electric Propulsion. New Frontiers mission: NASA medium-missions of intermediate size and cost between Discovery and large-class (flagship) missions. New Millennium: A now-discontinued technology development program initiated by NASA in 1995. NEX-SAG: Next Orbiter Science Analysis Group. NGRTG: New Generation Radioisotope Thermoelectric Generator (see RTG). NLSI: NASA Lunar Science Institute. NNSA: National Nuclear Security Administration. NOAA: National Oceanic and Atmospheric Association. Noachian epoch: The oldest of three time periods into which the geologic history of Mars has been divided, spanning from about 4.1 billion to about 3.5 billion years ago. NoDD: No Due Date, a type of research proposal has no specific submission deadline. Non-sidereal: The motion of a celestial body independent of that which appears to be caused by a planet’s rotation. NSF: National Science Foundation. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-6 

NSTC: National Near-Earth Object Preparedness Strategy and Action. NTP: Nuclear-Thermal Propulsion. Nucleobase (or Base): A class of compounds with ability to bond pairwise with each other and stack vertically These properties leads to the helical structure of DNA and RNA. The five primary nucleobases are guanine, cytosine, adenine, thymine, and uracil. Some viruses make use of aminoadenine in place of adenine, -O- Occultation: An event that occurs when one object is hidden by another object that passes between it and the observer. Contrast with a transit, when a smaller object passes in front of a larger one. Oort cloud: A spherical distribution of comets having semi major axes between 1,000 and 50,000 AU, typically with low orbital eccentricity. Ocean world: A planetary body having substantial amounts of liquid water on its surface or as a subsurface ocean. In the solar system, established examples include Earth, Calisto, Enceladus, Europa, Ganymede and Titan. ORR (Operational Readiness Review): During Phase D, examines the state of the built system and procedures to ensure that expectation match reality for the system and support hardware, software, personnel, procedures, and documentation. Opportunity: Second of the two rovers launched in 2003 to land on Mars and search for signs of ancient water. Organic detection: Processes to detect organic molecules. Organic molecule: A chemical that contains carbon and hydrogen bonds. OSIRIS-REx: Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer. A NASA mission currently returning a sample from the asteroid Bennu to Earth. Outgassing: Venting of gasses from the crust of a planetary body. Oxygenic photosynthesis: Photosynthesis during which oxygen is produced and released. -P- Paleoclimate: The climate of some former period of geologic time. Paleomagnetic: Area of study investigating the history of a planetary body’s magnetic field through rock and sediment. PD: Planetary defense. PDC: Planetary Defense Conference. Perchlorate: A salt containing the ClO4- ion. PESTO: Planetary Exploration Science Technology Office. Petrologic: Area of geology that studies the conditions under which rocks form. PHA: Potentially hazardous asteroid. Photodissociation/Photolysis: The breakup of molecules through exposure to light. Phylogenetic: Relating to the study of the evolutionary diversification of organisms over time. PICA: Phenolic-Impregnated Carbon Ablator. A thermal protection technology developed by NASA for spacecraft heatshields. PICASSO: Planetary Instrument Concepts for the Advancement of Solar System Observations. NASA program supporting the initial development of spacecraft-based instrument systems, covering TRL-1 to 3. Plagioclase: A group of minerals under the feldspar classification. Planetary Defense: Measures designed to protecte Earth from the hazards posed by the impact by asteroids and comets. Planetary protection: Measures designed to protect Earth and other planetary bodies from cross- contamination by biological materials carried on spacecraft. Planetesimal: A rocky and/or icy body a few kilometers to several tens of kilometers in size, which was formed in the protoplanetary nebula. Plasma: A highly ionized gas, consisting of almost equal numbers of free electrons and positive ions. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-7 

Porosity: The percentage of the total volume of a body that is made up of open spaces. Prebiotic: Relating to the chemical reactions that naturally occur in planetary environments that are important for the creation of biologically relevant compounds (e.g.,amino acids and sugars). Such reactions may be relevant to the origins of life. PRISM: Payloads and Research Investigations on the Surface of the Moon. PDR (Preliminary Design Review): A technical review held during Phase B of a project designed to demonstrates that a system’s preliminary design meets all requirements with acceptable risk and within cost and schedule constraints. Project Life-Cycle Phases: • Pre-Phase A: Concept studies. • Phase A: Concept and technology development. • Phase B: Preliminary design and technology completion. • Phase C: Final design and fabrication. • Phase D: System assembly, integration and test, launch and checkout. • Phase E: Operations and sustainment. • Phase F: Closeout. Protoplanet: A planet in the process of accretion from material in a protoplanetary disk. Protoplanetary disk: A circumstellar disk of matter, including gas and dust, from which planets may eventually form or be in the process of forming. Protoplanetary gas nebula: The phase in a star’s evolution before forming a planetary nebula. PRR (Production Readiness Review): During Phase C, held for Flight Systems and Ground Support projects typically with more than three systems. Determines readiness to produce the required number of systems. PSTAR: Planetary Science and Technology from Analog Research. NASA program addressing the need for field experiments to prepare human and robotic missions. Psyche: A NASA spacecraft scheduled to orbit the asteroid Psyche to investigate the origin of planetary cores. Plutonium-238 (238Pu): A radioactive isotope of plutonium decaying via the emission of an alpha particles and used as a source of heat and electrical power. Pyroclastic: Rocks that are composed solely or primarily of fragments of volcanic materials. -R- RAD: Radiation detecting instrument on the Mars Science Laboratory. Radiative balance: Accounting for all sources of ingoing and outgoing sources of radiation in a system. Radioisotope thermoelectric generator: nuclear power source using the heat produced by radioactive decay (typically Pu-238) to generate electricity. Radiolysis: The dissociation of molecules by ionizing radiation. Radionuclides: A radioactive nuclide. Redox reaction: Any of a large class of chemical reactions characterized by the reduction of one reactant and the simultaneous oxidation of another. Regolith: The layer of dust and fragmented rocky debris which forms the uppermost surface on many planets, satellites, and asteroids. It is formed by a variety of process including meteoritic impact. Rendezvous: Set of orbital maneuvers during which two spacecraft arrive at the same orbit and approach to a very close distance. Retrograde: Orbital motion in the opposite sense to the rotation of Earth and most of the other planetary bodies in the solar system. RF: Radio frequencies. Risk Classification: NASA’s four classes of risk for payload: PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-8 

• Class A: Highest priority, highest cost missions, which need to minimize risk as much as absolutely possible (e.g., Hubble, JWST). • Class B: High priority, high cost missions whose failure would be a major loss, also need to substantially minimize risk (e.g., Psyche, OSIRIS-REx). • Class C: Moderate priority, moderate cost missions that should mitigate risk but some risk can be tolerated (e.g., LRO, TESS). • Class D: Lower priority, lower cost missions that can afford to take on more substantial risk (e.g., LADEE, IRIS) RNA: Ribonucleic acid. A biopolymer similar to DNA whose single- or double-stranded helical structure is maintained by four nucleobases: adenine, uracil, cytosine, or guanine. Its principal role is to act as a messenger carrying instructions, encoded in DNA’s nucleobase pairs, for the synthesis of proteins. In some viruses, genetic information is encoded in RNA rather than DNA. RoI: Return on investment. ROSES: Research Opportunities in Space and Earth Sciences. NASA’s omnibus program for funding external research. Rosetta: An ESA spacecraft rendezvous with Comet 67P/Churyumov-Gerasimenko in 2014. RPS: Radioisotope power system. RTG: Radioisotope thermoelectric generator. -S- S&TU: Science and Technology Utilization. Saltation: A type of particle transport, occurring when loose materials are removed from a surface and carried by a fluid. SDT: Science Definition Team. Secondary Cratering: Cratering created from the projectiles during larger crater’s creation. SEP: Solar-electric propulsion. SESAME: Scientific Exploration Subsurface Access Mechanism for Europa. SHARAD: Mars Shallow Radar sounder. An instrument on Mars Reconnaissance Orbiter identifying water and ice deposits under the Mars surface. SIAD: Supersonic Inflatable Aerodynamic Decelerator. Siderophile: Organisms that require free iron to survive. SIMPLEX: Small Innovative Missions for Planetary Exploration. NASA’s class of very small, low-cost, higher-risk missions. SLS: Space Launch System. SMD: NASA’s Science Mission Directorate. SNL: Sandia National Laboratory. SO2: Sulfur dioxide. SOFIA: Stratospheric Observatory for Infrared Astronomy. Solar nebula: The cloud of gas and dust from which our Sun, the planets, and other bodies in the solar system formed. SoP: State of the profession. South Pole-Aitken Basin: The largest, deepest, and oldest impact basin on the Moon. Space weathering: Alteration of an atmosphereless planetary body’s surface materials by exposure to the space environment. Specific energy: Energy per unit mass. Spectral resolution: A measurement of the ability to resolve the features of an electromagnetic spectrum. SPHERE: Spectro-Polarimetric High-contrast Exoplanet Research. Instrument on ESA’s Very Large Telescope (VLT) providing images and characterization of exoplanets. Spectroscopy: The process of dissecting electromagnetic radiation from an object into its component wavelengths to determine its chemical composition. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-9 

Spectrum congestion: Radio signal integrity issues created when multiple stations transmit simultaneously on similar frequencies. SPLICE: Safe and Precise Landing Integrated Capabilities Evolution. SR: Strategic research. SRL: Sample Return Lander. SSERVI: Solar System Exploration Research Virtual Institute Stardust and Hayabusa missions: NASA and JAXA missions, respectively, whose purpose was to cometary coma and asteroid samples to Earth. STM: Science Traceability Matrix. STMD: NASA’s Space Technology Mission Directorate. Stratigraphic: Relating stratigraphy, an area of geology that investigates rock layers and their stratification. Subduction: Tectonic movement where one plate will move downward underneath another plate for recycling. Sublimation: The act of changing a substance directly from a solid to a gas without it passing through a liquid stage. Surface morphology: The structure and form of a particular surface. Swing-by: See gravity-assist maneuver. Synchrotron radiation: The electromagnetic radiation emitted when charged particles are accelerated, and typically used to create a source of intense X-ray for analytical purposes. SDR: System Definition Review, late in Phase A, following SRR, evaluates a proposed program’s ability to achieve its objectives. SIR: System Integration Review, end of Phase C, ensures that subsystems and components are available and ready to be integrated, and that personnel and facilities are equipped for integration. SRR: System Requirements Review, during Phase A, confirms that program requirements are well posed and align with agency strategic objectives. -T- TAGSAM: Touch and Go Sample Acquisition Mechanism, typically use to collect material from planetary bodies with very weak gravitational fields. TALOS: Thruster Advancement for Low-temperature Operation in Space. Development program for small and light thrusters operating at low-temperature. Taphonomic: Area of study that observes the processes of fossilization. TRL: Technology Readiness Level. Method of estimating the maturity of a technology. NASA defines 9 readiness levels, ranging from consistent with basic physical principles (TRL-1) to fully ready “flight proven” systems (TRL-9). Tectonism: The processes of faulting, folding, or other deformation of the lithosphere of a planetary body, often resulting from large-scale movements below the lithosphere. Terrain relative navigation: Autonomous localization and navigation based on the detection of specific terrain features with optical camera, radar or lidar systems. Terrestrial: Relating to the planet Earth. TESS: Transiting Exoplanet Survey Satellite. Tessera: Unique geological feature found on some of the plateau highlands on Venus and characterized by their extremely rugged topography. They are also known as complex ridged terrain and are believed to be formed when crustal stresses cause the surface to fold, buckle, and break. TPS: Thermal Protection Systems. Trans-Neptunian Region: The region of space that is further than the average distance of Neptune’s orbits. TRAPPIST: Transiting Planets and Planetesimals Small Telescope. TRAPPIST consists of a pair of robotic optical telescopes. One is located at La Silla Observatory in Chile and the other is at Oukaïmeden Observatory in Morocco. Trojans: Very small bodies located near the two stable gravitational points 60° preceding and following a planet in its orbit. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-10 

TRN: Terrain relative navigation. -U- UCIG: Utilization, Coordination, and Integration Group. UNCOPUOS: United Nations Committee on the Peaceful Uses of Outer Space. URC: Under Represented Communities. USGS: United States Geological Survey. UV: Ultraviolet. -V- Vibrational spectroscopy: see infrared spectroscopy. Volatile: A substance that vaporizes at a relatively low temperature. Volcanic resurfacing: Significant changes to a planetary object’s surface a due to the effects of volcanic activity. Voyager 2: A NASA probe launched to study the outer planets and space outside our solar system. V&V: Vision and Voyages for Planetary Science in the Decade 2013-2022, the second planetary science decadal survey. -W- WISE: Wide-field Infrared Survey Explorer. A NASA infrared space telescope launched in 2009. -X- X-ray Computed Tomography: An analytical technique used to determine the internal structure of an object via the convolution of X-ray images obtained from multiple vantage points. -Y- YORP: Yarkovsky-O’Keefe-Radzievskii-Paddack. This effect occurs when thermal emissions and the solar radiation reflected off the surface change the rotation state of an object in space. YORPD: Yearly Opportunities for Research in Planetary Defense. PREPUBLICATION COPY – SUBJECT TO FURTHER EDITORIAL CORRECTION F-11