Download Venus Entry Probe Initiative landing site proposal: a GIS approach

Proposal of different landing site options for the Venus Entry Probe (VEP)
Initiative.
Iván López and Francisco Carreño.
Geology Group-Laboratory for Remote Sensing and Planetary Research. Universidad
Rey Juan Carlos. C/Tulipán s/n. 28933-Móstoles. Madrid. Spain. E-mails:
[email protected]; [email protected].
1. Introduction
Earth and Venus are similar in size and bulk density but both planets seem to display
divergent evolutionary trends. The near global mapping of the surface of Venus (~ 98%)
carried out by the Magellan mission helped to constrain the structural and
morphological differences between different terrain types of Venus. A better
understanding of the magmatic and geodynamical evolution of Venus requires the study
the geochemical variability of the Venusian surface. Determination of the composition
and mineralogy of the surface is one of the principal scientific goals of the Venus Entry
Probe (VEP) Initiative. Of the many different study areas that can be considered we
propose several landing site options for further study by the VEP Landing Site Steering
Committee.
2. Proposal of landing sites.
2.1. Constraints on the composition of tessera-terrain materials and implications for
crustal plateau formation.
Tessera-terrain constitutes the oldest known crust material on Venus. This type of
terrain is characterized by intersecting sets of tectonic lineaments, a high relief relative
to surrounding materials and high surface roughness in radar images (e.g. Basilevsky et
al., 1986). Approximately 8% of the surface is covered by tessera-terrain but there is a
lack of composition data from previous missions, that landed on volcanic plains.
Because of this we propose that two of the four sites should be dedicated to the study of
tessera-terrain. Tessera-terrain is preserved in large crustal plateaus but also in locally
embayed kipukas in volcanic plains. These materials are the primary candidates for
evolved magmas on Venus. Tessera-terrain has been proposed to form a coherent layer
under the volcanic plains (e.g. Turcotte, 1993; Head and Basilevsky, 1998). Other
models (e.g. Hansen et al., 1999) propose that tessera-terrain is locally the oldest
material but not necessarily represent a unique layer formed in a particular moment of
the planet history. Geochemical sampling of two different tessera-terrain sites in
different parts of the planet could help to partially solve this problem. We propose two
different landing sites located in large crustal plateaus:
- Site 1: Ribbon bearing tessera-terrain in Ovda Regio. This area is located in
Aphrodite Terra and is Venus’ largest crustal plateau.
- Site 2: Tessera-terrain in Phoebe Regio. Phoebe Regio displays a deformational
history different to the rest of the crustal plateaus. This area is a region of
thickened crust and hotter than normal mantle that could support a plume origin
for this crustal plateau (Kiefer and Peterson, 2003).
2.2. Composition of shield terrain/shield plains.
Small volcanic shields cluster forming areas of high concentrations called shield plains
(Aubele, 1996) or shield terrain (Hansen, 2005). This type of shield-related material
covers large areas in the volcanic plains, and seems to have played an important role in
the volcanic resurfacing of Venus. With independence of the stratigraphic position of
the material the clustering of the shields and the monogenetic nature of each shield
points to a shallow crustal source (Hansen, 2005). It will be necessary to determinate
the composition of this volcanic materials to better understand the possible processes
that could originate this regionally important type of terrain.
2.3. Geochemical sampling of possible evolved materials: the case of Mahuea Tholus.
Mahuea Tholus (37.3°S, 165.1°E) is a very unusual volcanic feature with a diameter of
110 km located in Zhibek Planitia. This volcanic edifice is composed of bright, ridged
flows that stand about 600 meters above the surrounding plains. The thickness of these
flows and their several-hundred-meter ridge spacing could indicate the presence of
unusually viscous at the time of emplacement, and maybe indicative for the presence of
local petrologically evolved materials.
3. VEPGIS: a GIS tool for the selection of landing sites.
The use of Geographic Information Systems (GIS) allows the storage, analysis and
display of planetary georeferenced data. The great amount of data returned from
different sensors and missions make useful the use of such systems to study a particular
region and could help in the decision making process for the selection of study areas or
future landing sites. We propose to develop a GIS that help for the future process of
VEP landing site selection (initially named VEPGIS). The first step in this GIS
development will be to define the structure of the geodatabase and the different layers of
information that the system will display.
4. References.
- Aubele, J. (1996). Akkruva small shield plains; definition of a significant regional
plains unit on Venus. Lunar and Planetary Science Conference, 27, p.49-50.
- Basilevsky, A.T., A.A. Pronin, L.B. Ronca, V.P. Kryuchov, A.L. Sukhanov and M.S.
Markov (1986). Styles of tectonic deformation on Venus: Analysis of Venera 15 and 16
data. Journal of Geophysical Research, 91, p.399-411.
- Hansen, V.L., B.K. Banks and R.R. Ghent (1999). Tessera terrain and crustal plateaus,
Venus. Geology, 27, 1071-1074.
- Hansen, V.L. (2005). Venus’s shield terrain. GSA Bulletin, 117, p.808-822.
- Head, J.W. and A.T. Basilevsky (1998). Sequence of tectonic deformation in the
history of Venus: Evidence from global stratigraphic relations. Geology, 26, p.35-38.
- Kiefer, W.S. and K. Peterson (2003). Mantle and Crustal Structure in Phoebe Regio
and Devana Chasma, Venus. Geophysical Research Letters, 30 (1), 1005,
doi:10.1029/2002GL015762.
- Turcotte, D.L. (1993). An episodic hyphotesis for Venusian tectonics. Journal of
Geophysical Research, 98, p.17061-17068.