Table 1 Description of Upper Chaotic Terrain Unit (UCTU) members.

From: The Chaotic Terrains of Mercury Reveal a History of Planetary Volatile Retention and Loss in the Innermost Solar System

PLAINS MEMBERS

INTERCRATER REGIONS

Chaotic Plains Incipient [Cpin; Type area centered at 34° 00′ S, 24° 20′ W]: Plains, mostly situated within intercrater regions, which include widespread occurrences of low-relief knobs and shallow NW and NE-trending grooves.

Chaotic Plains Prominent [Cppr; Type area centered at 27° 00′ S, 28° 07′ W]: Plains, mostly situated within intercrater regions, which include clustered occurrences of prominent knobs and ridges. These features consistently trend to the NW and NE and are locally flanked or divided by similarly oriented grooves.

Chaotic Plains Extreme [Cpex; Type area centered at 30° 50′ S, 30° 50′ W]: Plains, mostly situated within intercrater regions, which consist of broad low-lying areas that retain faint groove markings, and contain low-density occurrences of scattered knobs and ridges; both typically having lower relief than similar Cppr features.

CRATER INTERIORS

Chaotic Crater Interior Incipient [Ccin; Type area centered at 27° 40′ S, 19° 30′ W]: Crater floors that include widespread occurrences of low-relief knobs and shallow NW and NE-trending grooves.

Chaotic Crater Interior Prominent [Ccip; Type area centered at 27° 45′ S, 24° 10′ W]: Crater floors consisting of extensive occurrences of topographically prominent, clustered knobs and ridges with lengths that consistently trend to the NW and NW. These features are locally flanked or divided by similarly oriented grooves.

Chaotic Crater Interior Extreme [Ccex; Type area centered at 29° 00′ S, 23° 28′ W]: Crater floors consisting of broad low-lying areas that retain faint groove markings, which separate scattered knobs and ridges.

CRATER RIM MEMBER

Chaotic Crater Rim Prominent [Ccrp; Type area centered at 28° 20′ S, 30° 24′ W]: Extensively breached crater rims (~ >50 km diameter) in which the breached sections align to the NW and NW regional trends. These topographic gaps separate high-relief knobs and ridges. Smooth plains, which are probably lavas, typically occupy the interior of these craters and embay the knobs and ridges.

  1. Note that each of these members’ descriptions is typical of their extents. However, their margins and some interior areas present variability due to the transitional nature of their contacts.
Back to article page