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| Amazonian epoch | |
|---|---|
| Name | Amazonian epoch |
| Type | geological epoch (Martian time) |
| Start | ~3.0 billion years ago |
| End | present |
| Preceding | Hesperian epoch |
| Following | Noachian epoch |
| Celestial body | Mars |
Amazonian epoch
The Amazonian epoch is a formal division of Martian geologic time used by planetary scientists to describe the most recent and longest-lasting interval of surficial and subsurface processes on Mars. In planetary stratigraphy it follows the Hesperian epoch and is characterized by comparatively low impact flux, reduced volcanic resurfacing, and extensive preservation of young geomorphic features observed by missions such as Mariner 9, Viking program, Mars Global Surveyor, Mars Reconnaissance Orbiter, and Mars Odyssey. Its name derives from the Amazonis Planitia region mapped by early telescopic and spacecraft investigations, and it frames interpretations made by teams from institutions including NASA, European Space Agency, and Jet Propulsion Laboratory.
The epoch is defined stratigraphically by crater-density chronologies calibrated against radiometric ages from lunar samples returned by the Apollo program and cross-referenced with crater production functions developed by researchers at Caltech, Brown University, and Smithsonian Astrophysical Observatory. Conventional estimates place its onset at roughly 3.0 billion years ago and continue to the present, although some studies propose subdivisions reflecting late Amazonian pulses tied to emplacement events recorded in units mapped by United States Geological Survey planetary geologists. The epoch’s temporal bounds are therefore reliant on absolute chronologies from comparative planetology and crater-count methods refined by teams at Arizona State University and the Planetary Science Institute.
Amazonian stratigraphy is dominated by finely preserved thin units, young lava flows, and widespread mantling deposits identified in global mapping efforts led by USGS and by regional studies in areas such as Elysium Planitia, Tharsis, Hellas Planitia, and Amazonis Planitia. Key stratigraphic markers include low-crater-density surfaces, superposed wrinkle ridges and lobate scarps mapped by MOLA topography from Mars Global Surveyor, and layered polar deposits observed by instruments aboard Mars Express and the Mars Reconnaissance Orbiter. Stratigraphers from California Institute of Technology and University of Arizona have used these markers to correlate units across quadrangles defined by USGS planetary geologists.
Active volcanic provinces such as Elysium Mons, Alba Mons, and smaller vents produced Amazonian lava flows recognized in spectral datasets from CRISM and thermal mapping by THEMIS. Tectonic deformation produced lobate scarps attributed to global contraction detected by SHARAD and radar instruments on Mars Reconnaissance Orbiter. Large impact events, including secondary modification of basins like Hellas Planitia and formation of younger craters such as Zunil crater, reshaped Amazonian surfaces. Periglacial and glacial processes in regions like Olympus Mons flanks and the Dorsa Argentea Formation were documented by research groups at University of Colorado and University of Bern.
During the Amazonian atmospheric pressure and temperatures are reconstructed as generally lower and colder than earlier epochs in studies by investigators affiliated with NASA Jet Propulsion Laboratory, Institut d'Astrophysique Spatiale, and Max Planck Institute for Solar System Research. Isotopic measurements of noble gases from analyses by teams using data from MAVEN and interpretations by University of California, Berkeley indicate progressive loss of volatiles to space, while episodic greenhouse episodes are hypothesized in localized warming scenarios invoked by researchers at Massachusetts Institute of Technology and Imperial College London. Atmospheric modeling efforts by groups at NCAR and University of Oxford explore interactions between dust storms catalogued by Opportunity (rover), Spirit (rover), and Curiosity (rover) missions and seasonal CO2 polar cycling observed by Mars Reconnaissance Orbiter.
Amazonian surfaces preserve youthful morphologies: rampart and fresh impact craters (e.g., Zunil crater), well-preserved lava flows in Elysium Planitia, lobate scarps linked to planetary contraction, and polygonal ground linked to periglacial processes seen in Utopia Planitia and Acidalia Planitia. Polar layered deposits, dune fields in Nili Patera and Gale Crater-adjacent basins, and recurring slope lineae studied by teams at NASA Ames Research Center and University of Hawaiʻi further typify Amazonian landforms. High-resolution imaging from HiRISE and topographic mapping by MOLA underpin morphological classifications used in regional syntheses by Brown University and University of Texas at Austin.
The Amazonian epoch’s generally cold, arid, and low-pressure conditions pose challenges for hypotheses of persistent surface habitability developed by researchers at SETI Institute and Lunar and Planetary Institute. Nonetheless, transient aqueous activity inferred from gullies, paleolacustrine deposits in craters mapped by European Space Agency science teams, and subsurface ice detected by SHARAD and neutron spectrometer data from Mars Odyssey motivate astrobiological targets prioritized by NASA Astrobiology Institute and mission planners for Perseverance (rover) and potential sample-return campaigns coordinated with NASA and ESA. Laboratory work at Smithsonian Institution and Caltech explores preservation potential of biosignatures in Amazonian-aged sediments.
Age estimates for Amazonian units rely on crater-count chronology models refined by researchers at Arizona State University and Planetary Science Institute, calibration against lunar samples from the Apollo program, and stratigraphic cross-cutting relations mapped by USGS planetary geologists. Absolute constraints derive from meteoritic analogs such as SNC meteorites studied at Johnson Space Center and radiometric work at institutions including University of New Mexico and Smithsonian Institution. Ongoing missions—MAVEN, Mars Reconnaissance Orbiter, ExoMars Trace Gas Orbiter—continue to supply datasets used by interdisciplinary teams at NASA, ESA, and academic centers worldwide to refine Amazonian chronologies.
Category:Mars epochs