BASALTIC VOLCANISM ON THE TERRESTRIAL PLANETARY BODIES

Basaltic volcanism in planetary history commonly represents secondary crustal material derived from partial melting of planetary mantles, and provides an important record of the mineralogical, rheological and thermal state of planetary mantles. Basaltic volcanism on Earth at divergent plate boundaries and hot spots forms the majority of the crust, and provides two distinctive eruption environments, subaerial and submarine. Initial observations of the Moon relied heavily on geomorphology to distinguish basaltic volcanism from other crustal materials. Returned samples have verified the role of basaltic volcanism on the Moon in its early history and increasingly sophisticated mineralogical remote sensing techniques have permitted the assessment of lunar volcanism in space and time. Theoretical analyses of basaltic magma ascent and eruption have provided criteria for recognition of the landforms and products of different eruption styles on the different planetary bodies. On Mars, very large quantities of flood-like basaltic volcanism dominate early crustal resurfacing and huge edifices mark the position of extremely long-lived plume-like activity extending to recent geological history in the Tharsis and Elysium regions. New high spatial and spectral resolution instruments are helping to link the SNC meteorites and surface units. The vast majority of Venus has been resurfaced by basaltic volcanism in the last 20% of its history, yet plate recycling was not operating during this time. Mercury represents one of the major unknowns in terms of the role of basaltic volcanism. Regional plains deposits appear to embay other crustal units, but definitive evidence of their basaltic volcanic origin has not been forthcoming. Could Mercury be without significant extrusive volcanism due to a crustal density filter to rising magma? The MESSENGER Mission to Mercury will help to resolve this conundrum and complete the picture of basaltic volcanism on the terrestrial planets.