Can Venus and Mars Inform Us About Intraplate Magmatism on Earth?

Abstract

Venus and Mars have operated as one-plate planets for some or all of their history and intraplate magmatic activity on Earth has been suggested as an analogue for the observed volcanic activity on these bodies. Flipping the question around, what can we learn about intraplate magmatism on Earth from other planets? Volcanic features, including extensive lava flows and vast lava plains, cover large portions of the Martian surface. Mars has two large volcanic provinces: Tharsis and Elysium. While the continent-sized region of elevated terrain called the Tharsis rise receives most of the attention, Elysium—the second largest volcanic province on Mars—is larger than the Ontong-Java plateau—the largest LIP on Earth. Activity detected by the InSight seismometer near Cerberus Fossae (located in Elysium Planitia, southeast of the Elysium volcanic province) is consistent with fluid flow at depth. Cerberus Fossae is among the youngest tectonic structures on Mars and large discharges of water and lava have been proposed to explain the geomorphic structures observed at Cerberus Fossae. The regional gravity and topography, volcanic history, and seismic activity at Cerberus Fossae are consistent with a present-day 2,000-km-radius plume head beneath Elysium Planitia. The characteristics of the Elysium Planitia plume are comparable to terrestrial plumes proposed to explain the formation of terrestrial LIPs. Plumes on Mars appear to be spatially stable for long periods of time, reflecting the stabilizing influence of a thick stagnant lid and sluggish mantle convection. While Venus is nearly the same size as Earth, there is no evidence supporting Earth-like plate tectonics for the past 250-750 Myrs. The similarity in size invites comparison of present-day volcanic activity between the two planets. This is complicated by the presence of plate tectonics where volcanic activity at ridges and subduction zones has no clear analogue on Venus. Expanding intraplate volcanism on Earth suggests as many as 100 active volcanic events per year on Venus. While detecting surface changes is one goal of the upcoming NASA and ESA Venus missions, surface change associated with volcanic activity has already been found in the Magellan image archive. Herrick and Hemsley identified a 2 km2 volcanic vent that changed shape in the eight months between two Magellan radar images. While sulfuric acid clouds obscure our view of the surface, those same clouds provide the best evidence for ongoing volcanic activity. Assuming the primary mechanism removing atmospheric SO2 is a reaction between calcium minerals on the surface and SO2, an SO2 residence time of ~2 Myrs is required. This requires an outgassing rate of ~6x1010 kg SO2/year—about the same yearly SO2 outgassing rate measured on Earth over the past decade. Converting this outgassing rate to erupted lava, an eruption rate on Venus of ~1 km3/yr is obtained.