Lunar and Planetary Science XXIX
1761.pdf
PHOTOGEOLOGIC MAPPING OF VENERA 13 AND 14 LANDING SITE REGION: VENUS. A.M. Abdrakhimov and
A.T. Basilevsky, Vernadsky Institute, Kogygin Str. 19, 117975, Moscow, Russia, [email protected].
Introduction: The mapping was done using Magellan C1- and
F-MIDRP's. The area under study (see Figure) includes the
Venera 13 and 14 landing circles, each ~300 km in diameter,
centered at 7.55°S, 303.69°E and at 13.05°S, 310.19°E respectively. At early stage of the Magellan data analysis the geology
of this area as well as areas of other Venara/Vega sites have
been studied by [4]. That time no model of regional and global
stratigraphy of Venus was sugested so the identified and
mapped geologic units were not regionally and globally correlated. Since that time the Venus stratigraphy model have been
suggested and tested in many areas of this planet [1]. The goal
of this work is to test if the mentioned global stratigraphy model
is applicable to the Venera 13/14 region and, if yes, what are the
stratigraphic positions of the surface materials chemically analyzed by the Venera 13 and 14 landers [3]. Our photogeologic
analysis led to the identification of nine material stratigraphic
units, which are correlatives to the units of [1]. Although some
uncertainties still exist the most probable is that Venera 13 sampled material of Plains with wrinkle ridges or young Lobate
plains while Venera 14 sampled material of young Lobate
plains.
Observation: The identified and mapped units are:
Tt - Tessera terrain material of the studied area looks similar to tessera material of other areas of Venus [1]. Tessera
forms islands standing over the surrounding plains and is embayed by their materials. Interpretation: Heavily deformed
material of unknown nature.
Pdf - Densely fractured plains material forms islands
among younger plains, has dense subparallel lineaments; Interpretation: Mafic lavas heavily deformed by extensional faults.
RB - Ridge Belts material forms plains of intermediate radar brightness, locally warped into broad linear ridges, embayed
by materials of younger plains. Interpretation: Mafic lava locally deformed by compressional deformation.
Psh - Shield Plains material formed by coalescing small
shields of 3 to 15 km across, embays Tt, Pdf, and RB and some
of younger plains, in some locations deformed by wrinkle
ridges. Interpretation: Fields of volcanic edifices partly separated by plains-forming floods.
Pwr - Materials of Plains with wrinkle ridges form generally smooth intermediate-dark to intermediate-bright areas complicated by wrinkle ridges. Pwr is divided into three age subunits. Interpretation: Mafic lavas deformed by moderate compressional deformation.
Ps - Smooth plains material forms smooth-looking areas
with diffuse boundaries, not deformed by wrinkle ridges. Wind
streaks are present locally. Interpretation: Fine reblown debris.
Pl - Lobate plains materials forms flow-like features looking either homogeneous (Pl1) or with variegated backscatter
(Pl2), not deformed by wrinkle ridges, associate with large volcanic edifices and rift zones. Interpretation: Mafic lava flows.
Cu - Crater materials form crater walls, floor, central peak,
ejecta blankets and outflows, all 12 craters of the area postdate
Pwr. Interpretation: Material of impact craters and their ejecta.
Sp - Splotch materials forms dark isometric spots on the
plains, postdate Pwr. Interpretation: Traces of air-shocks from
meteoroids destroyed in atmosphere [2].
Venera 13 landing circle is dominated with Pwr plains (4550%of the circle area) and Pl plains (~30%); areas of Ps
(~20%) and Pdf (<5%) plains are also present.
Venera 14 landing circle is dominated by lobate plains (8595%), also are present Psh plains (~5-10%) and remnants of
Pdf plains (<2%).
Conclusions: Thus the results of photogeologic analysis and
mapping showed that local stratigraphic units are correlative
with the units of regional and global stratigraphy of Venus [1].
Venera 13 had probably sampled either the material of Plains
with wrinkle ridges (Pwr) or Lobate plains (Pl). Venera 14 had
obviously sampled the material of Lobate plains (Pl).
References. 1) Basilevsky A.T. et al. Venus II, 1047-1086,
1997; 2) Schaber G.G. et al., JGR., 97, 13,257-13,301, 1992;
3) Surkov Yu.A. et al., JGR, 89, 393-402, 1984 4) Weitz
C.M.& Basilevsky A.T., JGR, 98,17,069-17,097, 1993.
Lunar and Planetary Science XXIX
VENERA 13 AND 14: GEOLOGIC UNITS: A.M. Abdrakhimov and A. T. Basilevsky
1761.pdf