Wednesday, August 5, 2015

Best evidence yet for active volcanism on Venus?


In an article from Geophysical Research Letters, a team led by Eugene Shaygin used images taken by the Venus Monitoring Camera (VMC) aboard Venus Express to identify transient hot spots on the surface. These hot spots are located near very young (~10 Mya) volcanoes and rifts, and are suggestive of active lava flows.

Even though the surface is generally obscured from view by the thick clouds, there is a transparent window through which light can pass in the near infrared wavelengths, and the VMC can capture images near 1 μm.

What Did They Find?

Examining VMC images of the Atla Regio region, the research team identified bright spots, i.e., areas where the local emissivity was significantly higher. These hot spots were first seen in VMC images from June 2008, and were gone again by October.

VMC images of Ganiki Chasma showing transient hot spots
They believe they have eliminated other possible sources for these hot spots, and they are confident the spots represent an increase in the surface temperature.

As additional supporting evidence, they point to Magellan spacecraft radar imagery.  Radar-dark parabolas are seen around impact craters on Venus, and are understood to represent deposited ejecta from the impact (more here in this paper by Campbell et al.). These parabolas are associated with the youngest impact craters, and believed to be among the youngest visible features on the planet. Magellan images of the same location show that the ejecta parabola associated with crater Stillwell is interrupted by what could be lighter colored lava flows that would post-date the fairly recent ejecta.

The authors believe these hot spots are volcanic in origin, and the body of evidence suggests that Venus is currently geodynamically active.

Why Is It Important?

If there are active volcanoes on Venus, it would be invaluable for future comparative studies of rocky worlds with ongoing volcanism. It could shed light on why the Earth and Venus evolved so differently, and help us learn more about the Earth in the process.


Shalygin, E., Markiewicz, W., Basilevsky, A., Titov, D., Ignatiev, N., & Head, J. (2015). Active volcanism on Venus in the Ganiki Chasma rift zone Geophysical Research Letters, 42 (12), 4762-4769 DOI: 10.1002/2015GL064088

Campbell, B., Campbell, D., Morgan, G., Carter, L., Nolan, M., & Chandler, J. (2015). Evidence for crater ejecta on Venus tessera terrain from Earth-based radar images Icarus, 250, 123-130 DOI: 10.1016/j.icarus.2014.11.025

Tuesday, August 4, 2015

Quick Look: Vertical profiles of H2O, H2SO4, and sulfuric acid concentration at 45–75 km on Venus

An improved model for vertical profiles of water and sulfuric acid vapors as well as sulfuric acid concentrations in the Venus clouds is presented.

From the April 2015 edition of Icarus:


Vertical profiles of H2O, H2SO4, and sulfuric acid concentration at 45–75 km on Venus


A method developed by Krasnopolsky and Pollack (Krasnopolsky, V.A., Pollack, J.B. [1994]. Icarus 109, 58–78) to model vertical profiles of H2O and H2SO4 vapors and sulfuric acid concentration in the Venus cloud layer has been updated with improved thermodynamic parameters for H2O and H2SO4 and reduced photochemical production of sulfuric acid. The model is applied to the global-mean conditions and those at the low latitudes and at 60°. Variations in eddy diffusion near the lower cloud boundary are used to simulate variability in the cloud properties and abundances of H2O and H2SO4 . The best version of the model for the global-mean condition results in a lower cloud boundary (LCB) at 47.5 km, H2SO4 peak abundance of 7.5 ppm at the LCB, and H2Omixing ratios of 7 ppm at 62 km and 3.5 ppm above 67 km. The model for low latitudes gives LCB at 48.5 km, the H2SO4 peak of 5 ppm, H2O of 8.5 ppm at 62 km and 3 ppm above 67 km. The model for 60° shows LCB at 46 km, the H2SO4 peak of 8.5 ppm, H2O of 9 ppm at 62 km and 4.5 ppm above 67 km. The calculated variability is induced by the proper changes in the production of sulfuric acid (by factors of 1.2 and 0.7 for the low latitudes and 60°, respectively) and reduction of eddy diffusion near 45 km relative to the value at 54 km by factors of 1.1, 3, and 4.5 for the low and middle (global-mean) latitudes and 60°, respectively. Concentration of sulfuric acid at the low and middle latitudes varies from ∼98% near 50 km to ∼80% at 60 km and then is almost constant at 79% at 70 km. Concentration at 60° is 98% at 50 km, 73% at 63 km, and 81% at 70 km. There is a reasonable agreement between the model results and observations except for the sulfuric acid concentration in the lower clouds. Variations of eddy diffusion in the lower cloud layer simulate variations in atmospheric dynamics and may induce strong variations in water vapor near the cloud tops. Variations in temperature may affect abundances of the H2O and H2SO4vapors as well.

Full Citation:

Krasnopolsky, V. (2015). Vertical profiles of H2O, H2SO4, and sulfuric acid concentration at 45–75km on Venus Icarus, 252, 327-333 DOI: 10.1016/j.icarus.2015.01.024