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| Mare Humorum | |
|---|---|
| Name | Mare Humorum |
| Diameter | 420 km |
| Eponym | Sea of Moisture |
Mare Humorum
Mare Humorum is a basaltic plain on the near side of the Moon located in the southwestern quadrant, recognized as one of the lunar mare that fill a large impact basin. The feature sits amid a network of highlands and basins including adjacent features such as Mare Nubium, Oceanus Procellarum, and the cratered regions leading toward Mare Cognitum. It has been a target for observational campaigns by telescopic observers such as Galileo Galilei and by space missions including Luna 9, Surveyor 3, and later orbiters like Clementine.
Mare Humorum occupies a roughly circular depression about 420 kilometres across within the southwestern near side and is bordered by rugged highland terrain that connects to the ejecta blankets of craters such as Gassendi, Vitello, and Doppelmayer. Its rim includes prominent massifs that correlate with features mapped by Wilhelm Beer and Johann Heinrich Mädler in 19th-century selenography and later refined by photographic atlases from George P. Bond and the United States Geological Survey. Observers from the era of Johannes Hevelius through the era of Giovanni Cassini recorded its dark basaltic tone, which contrasts with the anorthositic highlands documented in lunar sample studies returned by Apollo 12, Apollo 11, and robotic missions such as Luna 16.
The basin hosting this mare originated as a multi-ring impact basin formed during the basin-forming epoch; its morphology resembles other basins like Imbrium and Nectaris. The impact that created the depression likely involved a planetary-scale collision similar in energy to events that produced the South Pole–Aitken basin and Schrödinger basin, excavating crustal and upper mantle materials now exposed around its rim. Subsequent mare infill was caused by basaltic volcanism driven by partial melting of the mantle, a process also invoked for Mare Tranquillitatis and Mare Imbrium. Geophysical data from missions such as GRAIL and Lunar Reconnaissance Orbiter indicate variations in crustal thickness and mascon anomalies beneath the basin comparable to those underlying Mare Serenitatis.
The mare surface is dominated by low-viscosity mare basalts with phenocryst-poor textures closely related to basalts sampled in the Oceanus Procellarum region. Spectroscopic mapping by Clementine, Chandrayaan-1, and Kaguya reveals iron- and titanium-rich basalts in some locales and more feldspathic compositions near the marginal highlands, mirroring compositional gradients observed at Mare Crisium and Mare Vaporum. Notable geomorphological elements include wrinkle ridges, volcanic rilles, and mare-flooded craters such as Gassendi at the northeastern rim, which contains central peaks and terraces studied in comparison with features in Copernicus and Tycho. Ejecta deposits, secondary crater chains, and pyroclastic deposits inferred from infrared and ultraviolet remote sensing resemble those identified at sites like Aristarchus and Rimae Hyginus.
Telescopic observations from astronomers such as Galileo Galilei, William Herschel, and Johann Hieronymus Schröter established the basic albedo contrasts that differentiate mare regions; later systematic mapping by Mädler and the Smithsonian Astrophysical Observatory refined coordinates used by photographic surveys. The basin has been imaged at high resolution by Lunar Orbiter missions, by the Clementine multispectral mapper, and by the Lunar Reconnaissance Orbiter Camera, enabling comparisons with returned samples from Apollo and Luna programs. Gravity surveys from GRAIL and topographic profiles from the LOLA instrument have constrained subsurface structure and basin depth. While no crewed Apollo mission landed within this mare, robotic landers such as Luna 9 and orbiters including Chang'e 1 obtained data that inform models applied to this and analogous mare.
Crater counting and stratigraphic relations place the basin's formation in the pre-Imbrian to early Nectarian time interval, contemporaneous with basins like Mare Nectaris and older features such as the South Pole–Aitken basin. Mare basalt emplacement occurred later, during the Imbrian epoch, with ages overlapping basalts sampled at Mare Imbrium and Mare Serenitatis as determined by radiometric dating of returned Apollo and Luna samples and crater density calibration techniques developed from studies involving Apollo 16 and Apollo 17. Integrated chronologies using crater size-frequency distributions and isotopic constraints from radiogenic systems such as uranium-lead and samarium-neodymium provide absolute age estimates that link mare flooding episodes across the near side.
As a visually distinctive mare, it figured in early lunar cartography by Hevelius, Riccioli, and later cartographers whose names persist in modern selenography alongside features commemorating figures like Tycho Brahe and Johannes Kepler. Scientifically, the basin offers a natural laboratory for testing models of basin formation, mare volcanism, and crust-mantle differentiation, complementing investigations at Mare Imbrium and Mare Cognitum. Data from lunar sample curation facilities at institutions such as the Smithsonian Institution, NASA, and the Russian Academy of Sciences underpin comparative petrology studies. Contemporary missions by agencies including NASA, ESA, CNSA, and ISRO continue to refine its context within lunar evolution debates influenced by work from laboratories at MIT, Caltech, and the Max Planck Institute for Solar System Research.
Category:Lunar maria