Detecting volcanic ash of eruption plumes on Venus by imaging in the near infrared windows

Kurzfassung

Volcanic outgassing shapes the evolution of the atmospheres of terrestrial planets, but is itself affected by the atmospheric pressure (Head and Wilson 1986, Phillips et al. 2001, Gaillard and Scaillet 2014). Outgassing can take place in form of explosive eruptions where the exsolution of volatiles from ascending magma accelerates the ascent and drives further exsolution. Observations by Pioneer Venus and Venus Express show that the abundance of SO2 above the cloud layer (>70 km) varies by two to three orders of magnitude on timescales ranging from weeks to decades and one of the hypotheses brought forward is that explosive eruption plumes cause enhanced mixing between the SO2-rich (>100 ppm) lower atmosphere below the clouds, and the SO2-poor (<1 ppm) upper atmosphere above the clouds. (Esposito 1988, Marcq et al. 2013). Models of eruption plumes however show that only very intense eruptions originating at relative high elevations can reach this height (Glaze 1999). On Earth, eruptions of this intensity are rare, lower volume rate eruptions are more frequent. Plume height scales with volume rate (e.g. Glaze 1998, Airey et al. 2015). Thus there is a high probability that there are significantly more plumes that do not reach the cloud layer. Even if the SO2 variation has a non-volcanic origin, there is evidence suggesting explosive eruptions in form of diffuse deposits that are interpreted as being formed by pyroclastic flows from collapsing volcanic ash plumes (e.g Campbell et al. 2017). A re-analysis of Venera 13 descent spectroscopic measurements suggests the presence of particles that could be volcanic ash at altitudes around 4 km (Kulkarni et al. 2025).