Researchers re-analyze Magellan SAR data to explore mysteries in mountains of Venus

This is a radar image of one of the areas sampled on Ovda Regio.
There is a smooth ramp across the map going from higher to lower elevations,
shown as a gradual transition in radar brightness up the ramp.
The top of the ramp is brighter than the bottom of the ramp in the
lower right corner. The bright areas to either side of the
ramp are highland plateaus, and the curious dark spots are
the mysterious areas at the highest elevations that the researchers
are investigating.
Image credit: Elise Harrington / Allan Trieman / NASA.

Abstract: THE PUZZLE OF RADAR-BRIGHT HIGHLANDS ON VENUS:  A HIGH-SPATIAL RESOLUTION STUDY IN OVDA REGIO (2014 GSA Annual Meeting in Vancouver, British Columbia (19–22 October 2014))

Geological Society of America - Newsroom - Heavy Metal Frost? A New Look at a Venusian Mystery

Elise  Harrington;  Allan  Treiman (LPI) Radar-­‐bright  Highlands  on  Venus:  Confirmation  of  a  Ferroelectric  Substance 2014_August_Treiman.pdf  

Magellan Spacecraft

Mystery of ‘Metallic Frost’ in Venusian Mountains Deepens | Space Exploration | Sci-News.com
The idea that the Venusian highlands are covered in a ‘metallic frost’ dates back to 1995, when Dr Raymond Arvidson of the Washington University’s McDonnell Center for the Space Sciences and his colleagues were analyzing the rich archives of data taken from Magellan mission in the 1990's. Magellan’s primary objective was to map the surface of Venus using a technique known as synthetic aperture radar (SAR). SAR images taken of mountainous regions in the planet’s highlands revealed a mysterious brightening effect. Scientists surmised that this effect was due to a metal-containing ‘frost’ only a few millimeters in thickness frosting the mountains’ rugged surfaces.

Ms Harrington and her colleague, Dr Allan Trieman of Lunar and Planetary Institute,  re-purposed the old Magellan data.

• use of stereo radar elevation data rather than the lower resolution radar altimetry. increased their altimetry resolution from seeing patches 8 by 12 km to just 0.6 x 0.6 km.
• Magellan’s SAR, with its 75×75-m footprint, to look at radio reflectance, rather than the data on radio emissions from the surface, which had a coarser 15 by 23 km resolution.

They applied these to two areas in the Ovda Regio highlands region of Venus where they confirmed the same pattern of radar reflections brightening with increasing elevation, as was found by previous studies. The radar reflection was low at the lower 2.4 km elevation, then rapidly brightens up to 4.5 km. But they also found a lot more of those strange black spots, with a precipitous drop in the reflections at 4.7 km.

“Our data supports the interpretation that the radar properties of Ovda could be explained by the presence of ferroelectric substance at its surface,” the scientists said.

ASP: The Magellan Spacecraft at Venus

The Surface Features of Venus
Our knowledge concerning the surface of Venus comes from a limited amount of information obtained by the series of Russian Venera landers, and primarily from extensive radar imaging of the planet. The radar imaging of the planet has been performed both from Earth-based facilities and from space probes. The most extensive radar imaging was obtained from the Magellan orbiter in a 4-year period in the early 1990s. As a consequence, we now have a detailed radar picture of the surface of Venus. The adjacent animation shows the topography of the surface as determined using the Magellan synthetic aperture radar (black areas are regions not examined by Magellan). An MPEG movie (303 kB) of this animation is also available.

Overview of Surface

The surface of Venus is rather smooth in many places, though not nearly as smooth as originally expected . However, we find evidence for many of the same geological features found on Earth: canyons, volcanoes, lava flows, rift valleys, mountains, craters, and plains. There is substantial evidence for local tectonic activity but the surface appears to be a single crustal plate, with little evidence for large-scale horizontal motion of crustal plates as found on the Earth. Why the two planets differ in this aspect of their geology even though we believe them to have similar interiors is not well understood. The usual explanation is that Venus is a little behind the Earth in geological timescale, and its tectonic activity is just getting started. Much of the surface of Venus appears to be rather young. The global data set from radar imaging reveals a number of craters consistent with an average Venus surface age of 300 million to 500 million years.
There are two "continents", which are large regions several kilometers above the average elevation. These are called Istar Terra and Aphrodite Terra. They can be seen in the preceding animation as the large green, yellow, and red regions indicating higher elevation near the equator (Aphrodite Terra) and near the top (Ishtar Terra).