Pyroclastic flow deposits on Venus as indicators of renewed magmatic activity

Abstract

Radar bright deposits on Venus that have diffuse margins suggest eruptions that distribute debris over large areas due to ground‐hugging flows from plume collapse. We examine deposits in eastern Eistla, western Eistla, Phoebe, and Dione Regiones using Magellan data and Earth‐based radar maps. The radar bright units have no marginal lobes or other features consistent with viscous flow. Their morphology, radar echo strength, polarization properties, and microwave emissivity are consistent with mantling deposits composed of few centimeters or larger clasts. This debris traveled downhill up to ~100 km on modest slopes and blanketed lava flows and tectonic features to depths of tens of centimeters to a few meters over areas up to 40 × 103 km2. There is evidence for ongoing removal and exhumation of previously buried terrain. A newly identified occurrence is associated with a ridge belt south of Ushas Mons. We also note radar bright streaks of coarse material west of Rona Chasma that reflect the last traces of a deposit mobilized by winds from the formation of Mirabeau crater. If the radar bright units originate by the collapse of eruption columns, with coarse fragmental material entrained and fluidized by hot gases, then their extent suggests large erupted volatile (CO2 or H2O) amounts. We propose that these deposits reflect the early stage of renewed magmatic activity, with volatile‐rich, disrupted magma escaping through vents in fractured regions of the upper crust. Rapidly eroding under Venus surface conditions or buried by subsequent eruptions, these markers of recently renewed activity have disappeared from older regions.

Venus: The Atmosphere, Climate, Surface, Interior and Near-Space Environment of an Earth-Like Planet

“…The difficulty of making such observations through the cloud cover on Venus (Hashimoto and Imamura 2001;Mueller et al 2017) means that nearly all of the expected activity is below the threshold of detection for currently available optical and infrared techniques; here again, new dedicated missions will be required to obtain a basic inventory of current lava, gas and dust emissions. Meanwhile, studies by Campbell et al (2017) of Magellan radar images of deposits from volcanic plumes found that they erode rapidly in the harsh environment and overlay older deposits, the interpretation being that they mark some very young volcanically active regions on Venus.…”

Diffusion of volatiles in hot stagnant-lid regime planets

“…As such, it appears likely that the interior of Venus was originally volatile-bearing, has remained relatively hydrous and volatile-rich. An H2O and CO2-bearing Venusian interior is also supported indirectly by evidence for pyroclastic volcanism (Airey et al 2015;Campbell et al, 2017), and by geochemical modelling of limited surface composition data from Venera and Vega landers (Filiberto, 2014).…”

Volcanically extruded phosphides as an abiotic source of Venusian phosphine

“…Putative evidence for explosive volcanism on Venus has also been suggested from morphology and radar backscattering analysis, with some features consistent with pyroclastic flow deposits (44,45). In the analysis by Ghail and Wilson (44), the total eruption volume was estimated at about 225-875 km 3 , exceeding the volume of the Taupo, Yellowstone, and Toba calderaforming events; but they also noted that it may have been emplaced in more than one event.…”