Geophysical characterization of Venus' large topographic rises

Despite similarities in size and density, to Earth, Venus followed a very different evolutionary path, becoming warm and dry planet dominated by volcanic activity. While a series of new planetary missions (EnVision, Veritas, DaVinci) is preparing, it is necessary to develop new numerical tools and approaches allowing connecting the volcanic activity to the mantle dynamics and geophysical signatures.

 

The surface of Venus features a number of uplifted areas that are believed to be active manifestations of mantle plumes, perhaps analogous to Earth's hotspots or flood basalts (Smrekar and Parmentier, 1996). During the wave of numerical investigations of Venus in the 90s, Stofan et al. (1995) identified nine such large topographic rises (LTR). LTRs are defined by a pronounced, up to 2500 km wide, topographic bulge, associated volcanism and positive gravity, and some geophysical characteristics are provided by the study. However, their methodological approach is not easily reproducible, and cannot be applied to numerical models on a large scale. Consequently, we find ourselves in the need of a postprocessing algorithm that would provide geophysical characterization of these features. This approach needs to be fairly simple, but robust and reproducible. Furthermore, the approach needs to be easily applicable to both the observations, as well as numerical simulation outputs.

 

Our approach consists of three steps: detection of features similar to LTRs, their classification, and their geophysical characterization. First, we use the topography of Venus to detect isolated topographic bulges of extents between 1000 km and 2500 km. Then, we classify all detected features based on their uncorrelated gravity (Simons et al., 1997) and tectonic units present at their location (Ivanov et al., 2011). Finally, we outline the expected borders of their topographic and gravity signals, correct the data for the effects of the surrounding features, and compute their main geophysical characteristics. These characteristics include the total topographic volume, topography profiles, average topography, gravity profiles, and average gravity.

 

Preliminary global analysis of Venus' surface using our algorithm reveals a set of 30 LTRs which are then classified into 7 categories. Our set includes all LTRs mentioned by Stofan et al. (1995); however, we systematically predict slightly larger volumes of the features. Furthermore, we provide a comparison with regional geomorphological studies, where available.

 

References:

Ivanov et al., 2011, DOI: 10.1016/j.pss.2011.07.008

Simons et al., 1997, DOI: 10.1111/j.1365-246X.1997.tb00593.x

Smrekar and Parmentier, 1996, DOI: 10.1029/95JB02877

Stofan et al., 1995, DOI: 10.1029/95JE01834