Appendix F
Glossary and Acronyms
AAAC: Astronomy and Astrophysics Advisory Committee.
Abiosignature: A characteristic 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—that is, the basis of cloud formation.
Additive manufacturing: Set of manufacturing techniques based on adding layer-upon-layer of material. The most well known of such methods is 3D printing.
Aero-assist: Use of a body’s atmosphere to modify the trajectory of a spacecraft. Aerocapture is an example of such a maneuver.
Aerocapture: Deliberate use of an aerodynamic drag in an atmosphere to facilitate orbital capture of a spacecraft without the use of thrusters.
AIAA: American Institute of Aeronautics and Astronautics.
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, predecessor to SPLICE.
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.
Artemis: NASA’s current program to return humans to the Moon later this decade.
ASI: Agenzia Spaziale Italiana, the Italian space agency.
ASTROMAT: Astromaterials data system, NASA’s repository for extraterrestrial materials and laboratory data related to them.
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 the Jet Propulsion Laboratory, providing versatile mobility on planetary surfaces.
Biogenesis: The production of substances through biological processes.
Biosignature: A characteristic that can be interpreted as evidence of life.
Biosphere: The layer of a planet where life exists; the sum total of a planet’s ecosystems.
Biotic: Relating to life or living organisms.
Bistatic: A radar technique where the transmitter and receiver are at different locations.
BOE: Basis of estimate.
Bolide: An extremely bright meteor caused when an extraterrestrial body enters into and explodes in Earth’s atmosphere. Portions of the object’s body—meteorites—may survive to reach Earth’s surface.
Bouguer gravity: A gravitational anomaly that requires the incorporation of terrain height for correction.
Breccias: A type of sedimentary rock that comprises various minerals bound in a matrix that holds them together.
CAPTEM: Curation and Analysis Planning Team for Extraterrestrial Materials.
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 organism whose metabolism is supported via inorganic compounds derived from minerals.
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.
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).
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).
Co-I: Co-investigator.
COLDTech: Concepts for Ocean Worlds Life Detection Technology.
Corona: The outermost layer of a star.
CRISM: Compact Reconnaissance Imaging Spectrometer for Mars.
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 owing to internal heating.
CSA: Canadian Space Agency.
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 compound to give it properties more amenable to a particular analytical method.
Diagenesis: The physical and chemical changes occurring in sedimentary materials during and after rock formation at temperatures and pressures less than what is required for the formation of metamorphic rocks but that excludes surface alteration.
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.
DOE: Department of Energy.
Dragonfly: A NASA rotorcraft mission scheduled to be sent to Titan in the late 2020s.
Dynamo: An electromagnetic process in which the movement of conductive material gives rise to a magnetic field.
EAR: Export Administration Regulations.
Eccentricity: A measurement of the degree to which an elliptical orbit deviates from a circular orbit. An ellipse of zero eccentricity is a circle.
Egalitarianism: The idea that all people deserve equal opportunities.
EIL: NASA Johnson Space Center’s Experimental Impact Laboratory.
Electromagnetic sounding: Determination of variations in electrical conductivity with depth.
EM: Electromagnetic.
Endogenic: Relating to a process of internal origin.
Energy density: The amount of energy per unit volume.
EPO: Education and Public Outreach.
ESA: European Space Agency.
ESDMD: NASA’s Exploration Systems Development Mission Directorate.
ESSIO: NASA’s Exploration Science Strategy and Integration Office.
Europa Clipper: A large NASA multiflyby mission scheduled for launch to Europa in the mid-2020s.
EVA: Extravehicular activity.
ExMAG: Extraterrestrial Materials Assessment Group.
Exogenic: Relating to a process of external origin.
Exoplanets: Planets formed around stars other than the Sun.
Extremophile: An organism that is capable of living in extreme physical or chemical conditions, including high or low temperatures, high salinity, and intense radiation.
False negative: Results that wrongly indicate a negative result.
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.
FIB: Focused ion beam.
Flux: A measure of the energy or number of particles passing through unit area 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 system.
Ga: A billion years ago.
GBT: Green Bank Telescope.
GEISA: A spectroscopic database maintained by NASA.
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.
GitHub: A repository for software.
GNC: Guidance, navigation, and control.
GOES: Geostationary Operational Environmental Satellites.
GPHS: General-purpose heat source.
GPU (graphics processing unit): Specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the creation of images.
GRAIL (Gravity Recovery and Interior Laboratory): A NASA orbiter that investigated the Moon’s interior structure.
Graphene: Allotrope of carbon with desirable physical and electrical properties.
Gravity assist: Use of the relative movement and gravity of an astronomical object to alter the path and speed of a spacecraft.
GSFC: Goddard Space Flight Center.
GSSR: NASA’s Goldstone Solar System Radar.
Habitability, habitable: The ability of a planet to harbor life at some specific time, but it does not necessarily do so.
Habitable zone: The zone surrounding a star at which liquid water could exist on the surface of a planetary body with a sufficiently dense atmosphere.
Hadean: The first geologic eon on Earth, lasting from the planet’s formation 4.54 billion years ago to 4 billion years ago.
Hadley: A type of convective circulation pattern seen in planetary atmospheres.
Hayabusa 2: The JAXA sample-return mission to asteroid Ryugu.
HD&A: Hazard detection and avoidance.
HEEET: Heatshield for Extreme Entry Environment Technology.
HEOMD: Human Exploration and Operations Mission Directorate.
HIAD: Hypersonic Inflatable Aerodynamic Decelerator.
HIHT: High Irradiance, High Temperature.
HIITRAN: The high-resolution transmission molecular absorption database.
HLS: Human Landing System.
HOTTech (High Operating Temperature Technology): A NASA technology development program.
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.
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.
ISE: Initial Schedule Estimate.
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. A measure of how efficiently a reaction system creates thrust.
ISRO: Indian Space Research Organization.
ISRU: In Situ Resource Utilization.
ITAR: International Traffic in Arms Regulations.
JAMSTEC: Japan Agency for Marine-Earth Science and Technology
JAXA: Japan Aerospace Exploration Agency.
Jovian: Pertaining to the planet Jupiter or a similar-size exoplanet.
JPL: Jet Propulsion Laboratory.
JUICE: Jupiter Icy Moons Explorer. An ESA Ganymede orbiter mission scheduled for launch in the mid-2020s.
JWST (James Webb Space Telescope): A joint NASA-ESA 6.5-meter space telescope launched in December 2021.
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 searched for exoplanets using the transit technique.
Kerogen: 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.
LADEE: Lunar Atmosphere, Dust, and Environment Explorer.
LCRD: Laser Communications Relay Demonstration. NASA mission to showcase the use of optical communication in space.
LEAG: Lunar Exploration Analysis Group.
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 scarp: Curvilinear structure found on the surfaces of some planetary bodies.
LRO: Lunar Reconnaissance Orbiter.
LRV: Lunar Roving Vehicle.
M dwarf: Sometimes called “red dwarfs,” these stars are the smallest type on the main sequence.
Ma: A million years ago.
Macromolecule, macromolecular: Of or pertaining to a molecule—for example, 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.
MAPSIT: Mapping and Planetary Spatial Infrastructure Team.
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.
MAST (Mikulski Archive for Space Telescopes): A NASA repository for data from space astronomy missions.
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.
MEDA (Mars Environmental Dynamics Analyzer): Instrument 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.
MEDLI (Mars Entry, Descent and Landing Instrument): Used to monitor the performance of a spacecraft’s heatshield during atmospheric entry.
MEMS: Micro-electromechanical systems.
MEP: Mars Exploration Program.
MEPAG: Mars Exploration Program Analysis Group.
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 living organism to maintain structure, grow, and replicate.
MExAG: Mercury Exploration Assessment Group.
MMRTG: Multi-Mission Radioisotope Thermoelectric Generator converts the heat from the decay of radioactive plutonium-238 to electrical power.
MMX (Martian Moons Exploration): A Japanese mission to return samples from Phobos.
Monomer: A subunit of a polymer, when bonded to other identical subunits.
MOXIE (Mars Oxygen In Situ Resource Utilization Experiment): An oxygen-producing ISRU experiment on the Perseverance rover.
MSFC: NASA’s Marshall Space Flight Center.
MSR: Mars sample return.
Muon tomography: Use of cosmic ray muons to construct three-dimensional models of the density distribution in an object.
MWG: Modeling Working Group.
Nanomolar level: Measure of concentration of a given chemical component.
NASA: National Aeronautics and Space Administration.
Nascent: Emerging and coming into existence.
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.
Nebula: A cloud of gas and dust in space.
NED: Nuclear explosive device.
NEO: Near-Earth object.
NEOCam (Near-Earth Object Camera): The former name of NASA’s NEO Surveyor mission.
NEOWISE: The NEO-search phase of NASA’s Wide-field Infrared Survey Explorer mission.
NEP: Nuclear-electric propulsion.
New Frontiers mission: NASA missions of intermediate size and cost between Discovery and large-class (flagship) missions.
New Millennium: A now-discontinued technology demonstration 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 Administration.
Noachian: 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 that has no specific submission deadline.
Nonsidereal: The motion of a celestial body independent of that which appears to be caused by a planet’s rotation.
NSA (NASA Standard Assay): Procedure to verify spacecraft cleanliness for missions with bioburden requirements.
NSF: National Science Foundation.
NSTC: National Science and Technology Council.
NTP: Nuclear-thermal propulsion.
Nucleobase (or Base): A class of compounds with the ability to bond pairwise with each other and stack vertically. These properties lead 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.
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.
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, Callisto, Enceladus, Europa, Ganymede, and Titan.
Oort cloud: A spherical distribution of comets having semi-major axes between 1,000 and 50,000 AU, typically with low orbital eccentricity.
OPAG: Outer Planets Assessment Group.
Opportunity: Second of the two rovers launched in 2003 to land on Mars and search for signs of ancient water.
OPUS (Outer Planets Unified Search): A NASA database containing images and spectra of objects in the outer solar system.
Organic molecule: A chemical that contains carbon and hydrogen bonds.
ORR (operational readiness review): During Phase D, the state of the built system and procedures are examined to ensure that expectation match reality for the system and support hardware, software, personnel, procedures, and documentation.
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.
PAH: Polycyclic aromatic hydrocarbons
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.
Pan STARRS: Panoramic Survey Telescope and Rapid Response System.
PD (Planetary Defense): Measures designed to protect Earth from the hazards posed by the impact by asteroids and comets.
PDCO: NASA’s Planetary Defense Coordination Office.
PDR (Preliminary Design Review): A technical review held during Phase B of a project designed to demonstrate that a system’s preliminary design meets all requirements with acceptable risk and within cost and schedule constraints.
PDS (data): NASA’s Planetary Data System.
PDS (star): An astronomical object catalogued during a survey conducted at the Pico dos Dias Observatory in Brazil.
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.
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, and launch and checkout.
Phase E: Operations and sustainment.
Phase F: Closeout.
Photodissociation/Photolysis: The breakup of molecules through exposure to light.
Phylogenetic: Relating to the study of the evolutionary diversification of organisms over time.
PI: Principal investigator.
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 technology readiness level 1 to 3.
Plagioclase: A group of minerals under the feldspar classification.
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.
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.
Pre-Phase A: Concept studies.
PRISM: Payloads and Research Investigations on the Surface of the Moon.
Protoplanet: A planet in the process of accreating 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 the evolution of a protoplanetary disk prior to the dispersal of its gaseous component.
PSD: NASA’s Planetary Science Division.
PSTAR: Planetary Science and Technology from Analog Research. NASA program addressing the need for field experiments to prepare for 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: Materials that are composed solely or primarily of fragments of volcanic rocks.
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 Phase A: Plutonium-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 that forms the uppermost surface on many planets, satellites, and asteroids. It is formed by a variety of processes, including meteoritic impact.
RELAB: Reflectance Experiment Laboratory.
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 frequency.
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&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.
SAM: Sample Analysis at Mars instrument on the Curiosity rover.
SBAG: Small Bodies Assessment Group.
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: Those elements that tend to sink into a planets core rather than form part of its silicate crust.
SIMPLEx: Small Innovative Missions for Planetary Exploration. NASA’s class of very small, low-cost, high-risk missions.
SLS: Space Launch System.
SMD: NASA’s Science Mission Directorate.
SOFIA: Stratospheric Observatory for Infrared Astronomy.
Solar nebula: The cloud of gas and dust from which the Sun, the planets, and other bodies in the solar system were formed.
SOMD: NASA’s Space Operations Mission Directorate.
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.
SpecLib: Spectral Library.
Spectral resolution: A measurement of the ability to resolve the features of an electromagnetic spectrum.
Spectroscopy: The process of dissecting electromagnetic radiation from an object into its component wavelengths to determine its chemical composition.
Spectrum congestion: Radio signal integrity issues created when multiple sources transmit simultaneously on similar frequencies.
SPHERE (Spectro-Polarimetric High-Contrast Exoplanet Research): Instrument on the European Southern Observatory’s Very Large Telescope (VLT) providing images and characterization of exoplanets.
SPICE (Spacecraft, Planet, Instrument, Camera Matrix, Events): A series of files (known as kernels) containing ancillary data relating to the time, location, orientation, and other parameters describing the circumstances under which a specified instrument made specific observations.
SPLICE: Safe and Precise Landing Integrated Capabilities Evolution.
SR: Strategic research.
SRL: Sample Return Lander.
SRR (System Requirements Review): During Phase A, confirms that program requirements are well posed and align with agency strategic objectives.
SSERVI: Solar System Exploration Research Virtual Institute.
Stardust: NASA mission to return samples of a comet’s coma to Earth.
STMD: NASA’s Space Technology Mission Directorate.
Stratigraphy: An area of geology that investigates rock layers and their interpretation.
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.
Synestia: A rapidly rotating toroidal cloud of vaporized rock resulting from an impact between two planetary bodies.
TAGSAM (Touch and Go Sample Acquisition Mechanism): Typically used 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 temperatures.
Taphonomy, taphonomic: Of or relating to the study of processes that result in the formation, preservation, alteration, and destruction of biosignatures.
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.
TEM: Transmission electron microscopy.
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.
Tesserae: Unique geological features 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 system.
Trans-Neptunian Region: The region of space beyond 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.
TRL (technology readiness level): Method of estimating the maturity of a technology. NASA defines nine readiness levels, ranging from consistent with basic physical principles (TRL-1) to fully ready “flight proven” systems (TRL-9).
TRN (terrain relative navigation): Autonomous localization and navigation based on the detection of specific terrain features with optical camera, radar, or lidar systems.
Trojan: Very small body located near the two stable gravitational points 60 degrees preceding and following a planet in its orbit.
UCIG: Utilization, Coordination, and Integration Group.
UNCOPUOS: United Nations Committee on the Peaceful Uses of Outer Space.
URC: Under Represented Communities.
USGS: U.S. Geological Survey.
UV: Ultraviolet.
VEXAG: Venus Exploration Analysis Group.
Vibrational spectrometry: See infrared spectroscopy.
Volatile: A substance that vaporizes at a relatively low temperature.
Volcanic resurfacing: Significant changes to a planetary object’s surface owing to the effects of volcanic activity.
Voyager 1 and 2: NASA probes launched in the late 1970s to study the outer planets.
V&V: Vision and Voyages for Planetary Science in the Decade 2013–2022, the second planetary science decadal survey.
WISE (Wide-Field Infrared Survey Explorer): A NASA infrared space telescope launched in 2009.
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.
YORP (Yarkovsky-O’Keefe-Radzievskii-Paddack): This effect occurs when thermal emissions from and the solar radiation reflected off a surface change the rotation state of an object in space.
YORPD: Yearly Opportunities for Research in Planetary Defense.
