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Elysium Mons rises 14 km above the surrounding plains, while nearby Albor Tholus is 4 km high. Much of the quadrangle consists of plains near datum to –3,000 m, but in the east, Tartarus Montes, Tartarus Colles, and the rimmed depression, Orcus Patera, constitute a more rugged region, largely made up of knobs and low plateaus and ridges that separate Elysium Planitia from Amazonis Planitia to the east (MC-8). To the south of Orcus, Marte Vallis extends from Elysium Planitia into the Amazonis basin. Elysium Planitia includes the landing site of the InSight mission, which is exploring the interior of Mars using geophysical measurements.
The Phaethontis quadrangle is dominated by the cratered highlands of Terra Sirenum, which display prominent, marginal basins and tectonic structures, reaching thousands of kilometers in length. Except for the interiors of larger craters, elevations are generally 1–3 km above datum. Tharsis lava-flow materials inundate and partially cover the rugged, ancient terrain in the northeast corner of the quadrangle. Some of the structural basins in the northwestern part of the quadrangle display disrupted floors, referred to as chaotic terrain, most notably Atlantis Chaos and Gorgonum Chaos. The segmented, narrow graben systems of Sirenum Fossae and Icaria Fossae extend southwestward from the Tharsis rise, northeast of the quadrangle, cutting both ancient cratered highland materials and some of the older Tharsis lava flows.
The Iapygia quadrangle consists almost entirely of heavily cratered highlands, as high as 3 km above datum, descending to the northern basin rim (0–3 km below datum) and floor (3 to over 5 km below datum) of Hellas, and a piece of the southwestern rim of Isidis basin. Terra Sabaea makes up the western two-thirds of the quadrangle, whereas Tyrrhena Terra makes up the third that is east of a topographic divide, at ~75° E. An arcuate, north-facing series of scarps, Oenotria Scopuli, crosses this divide and appears to be concentric to Isidis basin. Huygens forms a prominent impact basin, with an outer rim of ~470 km in diameter, and it has an inner (250-km-diameter) and partial intermediate (350-km) ring.
The Amenthes quadrangle contains parts of the Martian southern highlands and northern lowlands, as well as the transition between the two. In the southern part of the quadrangle, Cimmeria and Tyrrhena Terrae form rugged, cratered plateaus as high as 1 km above datum, which are gouged by the long, linear depressions of Amenthes Fossae. Highland terrae in this quad are separated by Amenthes Planum, an elongate, topographic basin that is located as much as 1 km below the highlands. The northern part of the Amenthes quadrangle consists of southern Utopia Planitia, over 4 km below datum. The western part of the quadrangle is made up of eastern Isidis Planitia, which is nearly as low in elevation. Both Utopia and Isidis Planitiae – which are centered outside of the Amenthes quadrangle – are plains of sediments that fill very ancient impact basins. Various scarps and depressions mark the surface of these lowland planitiae. From south to north, the highland–lowland boundary is defined by distributed fields of knobs and intervening plains of Nepenthes Mensae, rolling plains of Nepenthes Planum, and isolated and coalesced depressions of Amenthes Cavi.
The Argyre basin spans the west half of the quadrangle, while part of Noachis Terra, at 0–2 km elevation, lies to the east. Argyre, as deep as –3 km elevation, is the best preserved of the largest multi-ringed impact basins on Mars, and is comparable in size to the Orientale basin of the Moon. The size and number of rings in the basin, which are generally expressed by discontinuous, concentric ridges and basin-facing scarps, are debated (three to seven rings or more), owing to later modification. The most common diameter assigned to a prominent, inner ring is 800–900 km, while the entire structure may be 1800 km or more across. Valleys drain toward Argyre from the south and east, while large channels may connect Argyre to the Uzboi–Ladon–Morava (see MC-19) system to the north. Drainage into the northwestern flank of the basin from surrounding plains is blocked by concentric, broad ridges. The hummocky floor of Argyre is 3–4 km below the average terrain elevation beyond the rim (Hiesinger and Head, 2002) and includes a variety of landforms. Noachis Terra is typical of the southern cratered highlands of Mars and gives its name to the oldest period of geologic time on Mars (MC-27).
Eridania quadrangle is composed almost entirely of the ancient cratered highland terrain of Terra Cimmeria, at 0–2 km elevation. The largest crater, Kepler, is about 230 km in diameter. Less-cratered, relatively low-lying plains are scattered throughout the quadrangle, including Eridania Planitia in the northwest corner and Planum Chronium in the southwest part of the quadrangle. Ridge systems occur throughout the quadrangle, with northeast-trending Eridania Scopulus forming the most prominent ridge.
Mars has attracted study ever since its motions were first apparent to ancient skywatchers. Summaries of early observations and ideas are listed in, e.g., Collins, 1971; Hartmann and Raper, 1974; Moore, 1977; Kieffer et al., 1992a; Martin et al., 1992; Sheehan, 1996; Morton, 2002. Hubbard (2011) gives an interesting example of the planning of Mars missions.
Mars is the fourth planet from the Sun and the outermost of the rocky, terrestrial planets that make up the inner solar system. Mars is the second smallest planet; only Mercury is smaller. Surface gravity on Mars is 3.71 m s–2, which is 37.6% that of the Earth. The present atmospheric pressure is low (~0.6 kPa) relative to Earth’s (101 kPa), and the atmosphere is mostly carbon dioxide (95%). The obliquity of Mars (tilt of the axis of rotation relative to the plane of orbit) is presently 25 degrees and may have varied by tens of degrees over the past tens of millions of years and longer (Laskar et al., 2004).
The Mare Acidalium quadrangle is dominated by the gently northward-dipping lowland plain of Acidalia Planitia and its contiguous southern neighbor, Chryse Planitia, both lying between 4,000 and 5,000 m below datum. These plains are partly bordered by cratered highlands that rise as much as 3,000 m above the plains – Arabia Terra to the southeast and Tempe Terra to the southwest. The outer margins of these terrae define the mouths of the largest fluvial-type channels anywhere on Mars – the circum-Chryse outflow channels (named for Chryse Planitia, into which the channels collectively emerge, see also MC-10 and MC-11). The regional planitiae contain the generally north–south trending ridge systems of Xanthe Dorsa. Acidalia Mensa is located in the center of the quadrangle and forms an irregularly shaped plateau that rises from 100 to >500 m above the surrounding plains.
The Arcadia quadrangle is dominated in the western part by fractured Alba Mons, the broadest volcanic shield on Mars, extending more than 2,000 km across and attaining nearly 10 km in relief above the northern plains. The eastern half of the quadrangle mostly consists of the rugged and troughed Tempe Terra. North of Tempe, the Vastitas Borealis plains slope down northeastward to the lowest point in the quadrangle, reaching 4,700 m below the Martian datum.
A mountain range, which has been informally referred to as the Thaumasia highlands, is prominent in the north-central part of the quadrangle; it lies at elevations of 4–7 km above datum, and forms the southern margin of the Thaumasia plateau (informal name; see Figure 4.2). Cratered highlands of Aonia Terra, interspersed with younger plains and basins, ranging from near datum to 4 km elevation, such as Icaria Planum and Aonia Planum, make up the rest of the area. The outer rim of the Argyre basin is just visible along the eastern edge of the quadrangle.
The western two-thirds of the Noachis quadrangle is dominated by the heavily cratered highlands of Noachis Terra (1–3 km elevation), which are bordered to the east by Hellas Planitia. The latter, as low as –7 km, forms the floor of the ~2,300-km-diameter Hellas basin. The highland–basin margin is marked by the arcuate Hellespontus Montes, composed of basin-ring ridge systems, hundreds of kilometers long. The southern part of the quadrangle consists of the high, ridged plains of Malea and Sisyphi Plana. Broad, lengthy but relatively subtle trough systems occur west of and concentric to Hellas basin.
This map spans diverse highland to lowland terrains from west to east. The western smooth region is the margin of the Tharsis rise that is centered to the west of the map, descending from 2 km to near datum. The elevated Lunae Planum and southern part of Tempe Terra occupy the central third of the map area. Lunae Planum rises to 3,500 m elevation along the southern border of the map as it approaches the Valles Marineris canyon system (south of the map area, MC-18). East of the planum lies the heavily cratered Xanthe Terra and Xanthe Montes. Cutting into these highlands are the large outflow channels Maja Valles and Kasei Valles. The latter originates from the irregular Echus Chasma depression that lies near datum. In the northeastern corner is Chryse Planitia, part of the vast northern lowlands, more than 3000 m below datum, and the destination for channel outflow as well as the Viking 1 lander.
Memnonia occurs on the western margin of the Tharsis volcanic province and on the southern margin of Amazonis Planitia. Its elevation ranges from a few kilometers above datum in Terra Sirenum to a few kilometers below datum along the northern edge of the map sheet. The cratered and faulted terrain of Terra Sirenum gives way to Tharsis lava flows to the east within Daedalia Planum. Valleys and channels mark the northern margin of the highlands, where they grade into low regions interrupted by elongate plateaus like Amazonis Mensa and the broader Lucus Planum.