A8. The Quads – South Low Belt

Geologic diversity. This latitude band spans Noachian highlands, Hesperian ridged plains, Amazonian lavas, and mega-canyon systems—often within a single quad. 

Dust & yardangs. Equatorial deposits of the Medusae Fossae Formation are among the largest single sources of martian dust, sculpted into vast yardang fields. 

Iconic science sites. Gale (sedimentary mountain and lake history), Gusev (basaltic plains + altered hills), Valles Marineris (layered canyon stratigraphy), and Margaritifer basins (deltas/aqueous deposits). 

⬛ Nu (ν) (0–30°S, 0–60°E)

Summary profile. Southern highlands bordering the prime meridian, dominated by ancient Terra Sabaea/Sinus Sabaeus uplands: rolling, cratered, with scattered valleys and wind-worked plains. The 0° longitude reference (Airy-0) lies here, embedded in crater Airy. 

Surface & geology. Heavily cratered Noachian crust with local channels and inter-crater plains; classic example craters include Dawes (~9°S, 38°E), whose walls and floor show dunes, valley cuts, and interior pits. Upland materials grade eastward toward Hesperian ridged plains; patchy mantles of dust/sand produce yardangs and bright/dark streaking.

Elevation & relief. Highlands stand hundreds to a few thousand meters above the martian datum with subdued local relief compared to canyon provinces farther west; MOLA data depict broad dome-like highs broken by old basins.

Atmosphere, weather & light. Frequent dust hazes; katabatic breezes over crater rims; sharp day–night thermal swings typical of low latitudes. Dust loading modulates sky brightness and reduces horizon contrast on many sols. (Generalized from low-latitude studies.)

Notable places. Airy-0 (the martian “Greenwich”), Dawes Crater and adjacent valleys. 

⬛ Xi (ξ) (0–30°S, 60–120°E)

Summary profile. Classical Mare Tyrrhenum/Iapygia–Tyrrhena Terra belt with archetypal Hesperia Planum ridged basaltic plains and the low, ancient volcanoes Tyrrhena Patera and Hadriacus Mons. 

Surface & geology.  Hesperia Planum (type area for the Hesperian Period) shows broad lava plains with wrinkle ridges; plains are interpreted as flood basalts, a key planetary stratigraphic marker.  Tyrrhena Patera (~20–22°S, ~106–108°E) and Hadriacus Mons (~31°S, ~92°E) are eroded, low-relief shield/patera edifices with radial channels and gullied flanks, recording volcano–water/ice interactions (e.g., Dao Vallis source).

Elevation & relief. Moderate-to-high standing uplands with plains benches and apron-like volcanic constructs; kilometer-scale relief over regional swells. 

Atmosphere, weather & light. Often clearer than canyon provinces; dust mantles and local devil tracks appear seasonally along ridged plains and volcano flanks. 

Notable places. Hesperia Planum, Tyrrhena Patera, Hadriacus Mons. 

⬛ Omicron (ο) (0–30°S, 120–180°E)

Summary profile. The Aeolis sector including two iconic rover sites: Gale Crater (Curiosity) and Gusev Crater (Spirit). Fluvial systems (Ma’adim Vallis) and Medusae-Fossae-related yardang fields fringe the belt. 

Surface & geology. Gale Crater (5.4°S, 137.8°E) hosts Aeolis Mons/Mount Sharp, a ~5.5-km-tall stratified mound archiving billions of years of climate and sedimentation. Gusev Crater (14.6°S, 175.4°E) receives Ma’adim Vallis; Spirit found mainly basaltic plains, with aqueously altered materials in Columbia Hills. Ma’adim Vallis head and trunk span the southern highlands toward Gusev, an outflow channel marking catastrophic releases.

Elevation & relief. Transitional—highland crater rims and mesas about lower, smoother plains; interior mounds (Gale) amplify local relief to multi-kilometer scale.

Atmosphere, weather & light. Regular dust devils and track fields documented (especially Gusev); variable haze affects insolation and visibility near yardang provinces.

Notable places. Gale/Aeolis Mons, Gusev, Ma’adim Vallis. 

⬛ Pi (π) (0–30°S, 180–240°E)

Summary profile. Tharsis-foreland to Memnonia/Syria–Claritas sector: volcanic plains (Daedalia Planum), broad tectonic troughs, and the western reaches of equatorial mantles including parts of the Medusae Fossae Formation (MFF).

Surface & geology. Daedalia Planum south of Arsia Mons is a lava-flooded plain with overlapping flow fields and low cones; surfaces range from Amazonian to Hesperian in age. The Medusae Fossae Formation—a huge, friable, equatorial deposit with yardangs—likely volcanic/pyroclastic and a major martian dust source. Nearby outflow channels (e.g., Mangala Valles) incise and crosscut plains, linking tectonics to catastrophic floods.

Elevation & relief. Gently sloping volcanic aprons with local tectonic scarps and fossae; kilometer-scale plateaus step down toward the equator.

Atmosphere, weather & light. Frequent dust lifting over MFF and dark lavas; thin, wind-sculpted landforms testify to persistent eolian activity and reduced surface contrast during dusty episodes.

Notable places. Daedalia Planum, Medusae Fossae (Lucus/Gordii Dorsum reaches), Mangala Valles.

⬛ Rho (ρ) (0–30°S, 240–300°E)

Summary profile. The western–central Valles Marineris province and Phoenicis–Syria–Claritas highlands: faulted plateaus, graben swarms, and canyon heads (Noctis Labyrinthus) transitioning east into the great chasmata.

Surface & geology. Noctis Labyrinthus (~6–8°S, ~260–265°E): maze-like graben and subsidence blocks with diverse hydrated minerals, sitting at the canyon system’s western gateway. Eastern Rho merges into Ophir, Candor, and Melas Chasmata—steep-walled troughs with layered deposits, mass-wasting fans, and interior mounds.

Elevation & relief. Among Mars’s greatest relief contrasts: plateau tops vs. canyon floors differ by several kilometers, with cliffed walls and stair-stepped benches.

Atmosphere, weather & light. Topographic channeling drives canyon winds and dust lifting; frequent hazes reduce direct light and accentuate warm-hued sky scattering.

Notable places. Noctis Labyrinthus, west/central Valles Marineris segments (Ophir–Candor–Melas).

⬛ Sigma (σ) (0–30°S, 300–360°E)

Summary profile. Transition from eastern Valles Marineris into Margaritifer Terra/Sinus Sabaeus: chaos terrains and outflow source regions feeding toward Chryse, plus classic crater basins with deltaic deposits.

Surface & geology. Iani Chaos (~2°S, ~342°E): fractured, subsided blocks thought to form by removal of subsurface volatiles; headwaters to Ares Vallis.  Holden Crater (~26°S, ~326°E) and Eberswalde Crater (~24°S, ~326–327°E) preserve layered sediments; Eberswalde contains a textbook fan delta. Eastern Valles Marineris termini (Coprates/Capri/Eos) grade to chaotic basins and outflow channels.

Elevation & relief. From chasma floors up to highland rims; deltas sit on crater floors hundreds to thousands of meters below surrounding uplands. 

Atmosphere, weather & light. Dust-laden breezes through chaos/outflow corridors; variable visibility and strong horizon color during dusty seasons. Stratified walls accentuate long, raking light near sunrise/sunset. 

Notable places. Iani Chaos, Holden (ULM system) and Eberswalde deltas, eastern Valles Marineris mouths.