Bright highlands in equatorial Venus likely ferro-electric. What's up with the high-latitude highlands?

Overview

A lot of papers have been written about the highly reflective highlands (in radar) on Venus, with several different hypotheses (e.g. high porosity, metal frost).  Allan Treiman, Elise Harrington, and Virgil Sharpton look specifically at high-latitude highlands in comparison to highlands in the equatorial regions.  Both areas feature high reflectivity, but the reflectance patterns are distinct, as they describe in Venus' radar-bright highlands: Different signatures and materials on Ovda Regio and on Maxwell Montes.

What Did They Find?

They have confirmed earlier studies showing that the reflectance pattern seen in equatorial highlands

"Snow Line" from N flank of Maxwell Montes (from Fig. 4c)

(such as Ovda Regio) are consistent with a ferro-electric substance, likely chlorapatite.

The reflectance patterns on Maxwell Montes (~60°N) are different.  The backscatter abruptly transitions from low to high at the previously identified "snow line" (~4.5km elevation), and stays high above that point.

They believe this pattern indicates a semiconductor material.  How did it get there? Either by precipitation from the atmosphere (frost?), or it formed as the result of a chemical reaction between the surface and atmosphere.

Why Is It Important?

At the very least, their research shows that even though the highlands of Ovda Regio (equatorial) and Maxwell Montes (high latitude) are similarly reflective, they are caused by different materials or processes.

The authors urge (and I agree) that lander missions with geochemical analysis instruments be sent to multiple highland locations.

References:

• Treiman, A., Harrington, E., & Sharpton, V. (2016). Venus’ radar-bright highlands: Different signatures and materials on Ovda Regio and on Maxwell Montes Icarus, 280, 172-182 DOI: 10.1016/j.icarus.2016.07.001

Discovery of a 150 day period in the Venus condensational clouds

Overview

Using near infrared (NIR) data from the VIRTIS instrument that once traveled aboard the Venus Express spacecraft, Kevin McGouldrick and Constantine C. C. Tsang found a periodic variation in radiance, most intense at the mid-latitudes.  The paper is here.

What Did They Find?

They identified A 150-day periodic variation in radiance within the 1.74 µm and 2.30 µm windows, which is most pronounced between 30° and 60° latitude.  They also found that in these mid-latitudes, radiance at these wavelengths steadily increased throughout the life of the instrument. 

Why Is It Important?

The 150-day timescale is consistent with a model (developed by McGouldrick) of the Venusian condensational clouds vertical structure, driven by radiative-dynamical feedback.  I'm not sure what that means, but thank goodness the paper is open source!

References

• McGouldrick, K., & Tsang, C. (2017). Discovery of a 150 day period in the Venus condensational clouds Icarus, 286, 118-133 DOI: 10.1016/j.icarus.2016.10.005

Venus Research at LPSC 2017

Thursday afternoon at #LPSC2017 was Venus time! Thirteen oral presentations were presented, including topics such as:

• Atmosphere observed by NASA's SOFIA Telescope
• Metal frost
• Recent volcanism
• Earth-based Experiments & Modeling

You can read the program which includes links to all the abstracts.

Posters, too!  Yes, there were a 28 posters dealing with science and future exploration of Venus.  The program with links to abstracts are available for these, too.

Six of these posters were uploaded to the LPSC website for you to see.  Here are direct links to two of them:

• Actively Cooled Venus Lander Instrument Payload Using a Multi-Cascade Refrigeration Cycle

• Morphometry of Mid-Sized Venusian Shield Volcanoes

Best evidence yet for active volcanism on Venus?

Overview

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.

References:

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

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:

Title:

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

Abstract:

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