User:Hamsquirrel/Volcanism on Venus

Recent volcanic activity
Volcanism on Venus has taken place within the last 2.5 million years; however, there is no absolute proof that any volcano on Venus has erupted recently. Recent radar imagery shows more than 1,000 volcanic structures and evidence of possible periodic resurfacing of the planet by floods of lava. In addition to the radar images, there is supporting evidence that volcanism has taken place, including an unusual change in the amount of sulphur dioxide gas in the upper atmosphere. Sulphur dioxide is an important component of volcanic outgassing. However, the sulphur dioxide in the lower atmosphere remains stable. This could mean that a change in the global atmosphere caused the sulphur dioxide concentration to increase above the clouds. Even though the change in the atmosphere may be evidence that there have been volcanoes that erupted in Venus, it is difficult to determine whether they occurred or not. In March 2014, the first direct evidence for ongoing volcanism was located, in the form of infrared "flashes" over the edges of rift zone Ganis Chasma, near the shield volcano Sapas Mons. These flashes were detectable during two or three consecutive Earth days in 2008 and 2009 and are thought to be caused either by hot gases or lava released from volcanic eruptions. Scientists suspect that there are three volcanoes that may be active: Maat Mons, Ozza Mons and Sapas Mons.

In 2020, a study by University of Maryland supported by Swiss National Science Foundation and NASA discovered that 37 of Venus coronae show signs of ongoing activity. Maryland professor Laurent Montesi said, "we are able to point to specific structures and say ‘Look, this is not an ancient volcano but one that is active today, dormant perhaps, but not dead..." The active coronae are clustered near each other, so positioning geologic survey instruments would now be easier.

Lightning
Lightning on Venus may serve as a diagnostic of volcanism or atmospheric convection, so some effort has been devoted to detecting possible lightning on Venus. No lightning has been directly observed, but the most compelling evidence is the very low frequency (VLF) radio emissions recorded beneath the clouds by all four of the Venera landers. The Japanese orbiter Akatsuki is currently searching for visible lightning on Venus, among other science objectives.

Exploration
In April 2010, Suzanne E. Smrekar et al. published that Venus Express observed three volcanoes that have had eruptions about 250,000 years ago or less, which suggests that Venus is periodically resurfaced by lava flows. She has proposed two missions to Venus to elucidate the planet: Venus Origins Explorer (VOX), and VERITAS. Meanwhile, the Japanese spacecraft Akatsuki has been orbiting Venus since December 2015 and one of its goals is to scan for active volcanism using its infrared cameras, although the infrared detector that was supposed to do this failed in December 2016 after a relatively short period of observations.

Atmospheric phosphine
In 2020, Greaves et al. detected phosphine levels of 1-5 PPB in Venus' atmosphere using ALMA and JCMT. Historic data from Pioneer Venus also shows the possible detection of phosphine. Phosphine (PH3) is derived from Phosphide (P3-) through the following interaction with sulfuric acid in Venus’ atmosphere:

2 P3- + 3HsSO4 = 2PH3 + 3SO42-

Phosphide comes from metals such as iron and magnesium, which should exist in great quantities in Venus’ mantle. The phosphines were detected at a height of 70km, which implies a volcanic eruption on the explosive scale of Krakatau or Yellowstone on Earth. The implication of this is not only that Venus has experienced recent volcanism, but that it is capable of explosive eruptions despite the lack of hydrated melts created at subduction zones on Earth. It is thought that Venus may have primordial water in the mantle that could be concentrated through fractionation.

Biological activity has been suggested as an alternate explanation for the phosphines in Venus’ atmosphere, but this is unlikely due to the absence of any other biosignatures. Another hypothesis states that the phosphine could be produced in Venus’ clouds, but this process requires water which is generally unavailable on Venus. Some scientists question that the phosphine levels found are truly as high as indicated. If the phosphine is present in amounts of 1-5 PPB and can be determined to originate in the mantle, it will imply a deep mantle plume system which contains enough volatiles to produce explosive volcanism.