ARTEMIS, VENUS, THE LARGEST TECTONOMAGMATIC FEATURE IN THE SOLAR SYSTEM?

Artemis includes an interior high surrounded by a large (2100 km diameter) narrow (25-100 km) deep (1-2 km) circular trough (Artemis Chasma), and an outer rise that grades outward to the lowland. Results of new 1:10M geologic mapping of Niobe and Aphrodite (57N-57S; 60-180E), reveals that Artemis comprises a much larger feature than previously recognized, including: a wide outer trough (>5000 km diameter), a huge radial dike swarm (12000 km diameter), and a concentric wrinkle ridge suite (13000 km diameter). Radial fractures predate the emplacement of local cover deposits—cut in turn by wrinkle ridges. Fracture and wrinkle ridge suites cut crustal plateaus Ovda and Thetis of western Aphrodite, but they are cut, in turn, by Aphrodite fracture (rift) zones.

Artemis evolution included: 1) doming and magma intrusion via radial dikes; with 2) radial fracture propagation well beyond the central dome driven by magma loading; 3) local surface escape of magma buried portions of the radial fracture suite; 4) wrinkle ridges deformed these local cover deposits due to coupling of convective mantle flow to the lithosphere; 5) late formation of the outer trough. Artemis Chasma and its interior evolved broadly coeval with concentric wrinkle ridges and radial fractures immediately adjacent to the chasma, and thus were coeval with the above events. We suggest that Artemis (covering ~1/3 of Venus) represents the signature of a deep mantle plume on relatively thin global lithosphere. Recognition of Artemis’ giant radial fracture suite and wrinkle ridge suites, due in part to cartographic serendipity that Artemis lies almost completely within the Niobe and Aphrodite 1:10M map sheets, highlights the importance of viewing regional-scale mapping in virtual global space. The newly recognized extent of Artemis holds implications for the formation of giant radial dikes warms, wrinkle ridge formation, terrestrial planet mantle-lithosphere coupling, and Venus surface and geodynamic evolution.