TWO REGIONAL FAULT BELTS. G. A. Burba, Vernadsky Institute of Geochemistry and Analytical
Chemistry, Russia’s Academy of Sciences, 19 Kosygin St., Moscow 119991, Russia <[email protected]>.
Introduction: A rimmed depression in Asteria
Regio on Venus have been named Nikolaeva Patera.
The naming was done in 2005 by the International
Astronomical Union in commemoration of Dr. Olga
Nikolaeva, Russian planetologist and geochemist.
The feature is located within the area of ancient terrains, but possess clear signs of younger geologic
activity. It is located at the intersection of the two
long, regional-scale fault belts, one of which is connected with the formation of Beta Regio upland.
The name origin: Nikolaeva Patera is named
after Olga Vladimirovna Nikolaeva (1941–2000),
who was a planetologist-geochemist at the Laboratory of Comparative Planetology, Vernadsky Institute, Russian Academy of Sciences. During 26 years
she was involved in the planetary research. Her main
field was geology and geochemistry of Venus, including both atmosphere and surface of this planet.
Her main results in planetology include:
► development of the engineering model of lunar
soil for the spacecraft design and landing (1974);
► discovering (with Venera 8–14 landers data) the
diurnal variation process of the cloud cover of Venus – the geochemical cycle and day-to-night change
in thickness of the cloud layer (1976);
► the first (and still the only) in situ measurements of the chemical data within the near-surface
layer of Venus atmosphere, done with “Contrast”
geochemical indicator designed and built by Olga
(two patents for invention obtained); this indicator
provided the unique data on the redox (reductionoxidation) conditions in the layer as close as 15 cm
from the planet’s superheated surface (Venera-13
and Venera-14 landers, 1982);
► estimations of terrestrial counterparts for the
types of Venus rocks after their natural radioactive
elements K, U and Th content (1982, 1997);
► development of geochemical aspects of Venus
geology in application for the layered rocks origin
(lava emplacement vs. sedimentation) – after the
Venera landers’ close-up panoramic images (1983);
► definition of arachnoids as the specific class of
endogenic geologic structures after the Venera-15
and Venera-16 SAR images (1986);
► definition of geochemical uniqueness of the
rock type at Venera-8 landing site as Na-alkaline
syenites (1983), which proposed as evidence of a
continental crust on Venus (1990), and pancake
domes suggested as source of such rocks (1992).
The naming of feature on Venus after Olga
Nikolaeva have been done on the proposal of Prof.
V.I. Feldman (Geological Department, Lomonosov
Moscow State University).
Fig. 1. Side-looking radar image of Nikolaeva
Patera area on Venus. Area size is 400 x 480 km.
SAR image: Magellan/NASA.
Fig. 2. Interpretation of Nikolaeva Patera area.
Segments of fault belts (A, B) divide tessera terrain
into separate patches (T). Lobate flows (L) run SE
outwards the Patera rim (black line). White sinuous
lines are narrow trenches within the fault belts. Lines
with black dots – wide trenches with flat bottom.
White circles – “pancake” domes (volcanoes).
Geographic description: Nikolaeva Patera is
located NW of Beta Regio within the northern part
of Asteria Regio. The center of patera is at 33.8°N
latitude and 267.5°E longitude. As a whole this
patera have an elongated shape with long axis 100
km and short axis 60 km. The feature consists of
three oval-shaped depressions, which are nested
within the joint rim (Fig. 1). Elongation is in NE –
SW direction, which is along the same way as the
narrow trenches of Agrona Linea fault belt (labeled
A on Fig. 2). Nikolaeva Patera marks the SW end of
this belt. Agrona Linea fault belt could be clearly
traced from Nikolaeva Patera for 2300 km to the NE,
then to E and SE around the northern outhills of Beta
Regio upland. Patches of Sudenitsa Tesserae surround Nikolaeva Patera from every quarter.
Geological setting: Most ancient terrains in the
vicinity of Nikolaeva Patera are patches of tessera –
bright rugged areas located higher than dark plain
terrains (Fig. 3). The latter are next in age. Dark
plains fill the areas between tessara patches, embaying tessera. These plains in some areas undergone a
tectonic reworking with numerous narrow sinuous
trenches, which form elongated fault belts. The belts
are younger in age than the dark plain areas. There
are two main fault belts in the area. One of them
have NE–SW direction and its segment located NE
from Nikolaeva Patera belongs to Agrona Linea,
which is circum-Northern Beta Regio fractute zone.
Another fault belt in the area have NW–SE direction
with further changing its running to E (Fig. 4).
There are clear evidences of volcanic activity
within Nikolaeva Patera and in the area adjusent to
its rim. Small domes, both conical and flat-topped
(“pancake”), are on patera bottom and on its rim. To
the SE of patera there is a plain area with lobate
flows running radial outwards the patera (Fig. 2).
They looks to be originated from the patera’s rim.
Interpretation: Nikolaeva Patera sits at the
junction of the two regional fault belts. Such position reflects the origin of the patera, which occupies
most disturbed and so a weak spot of a crust in the
area, being at the intersection of the two zones of
disturbation, marked on the surface with numerous
trenches. These trenches should resulted from the
extension of the planetary crust. The NE – SW belt
position is concentric to Beta Regio. So, the uprising
of Beta Regio upland could be a cause for the formation of this belt.
The weak spot of a crust provided a channel for
the interior material upwelling, which resulted in
volcanic activity and formation of the rimmed depression of Nikolaeva Patera. As a whole Nikolaeva
Patera looks like a small corona-type feature.
Fig. 3. Asteria Regio area radar image. Area
size is 1500 x 1700 km.
SAR image: Magellan/NASA.
Fig. 4. Interpretation of regional linear features
in Asteria Regio. Nikolaeva Patera is located at the
junction of the two regional fault belts. The borders
of these belts are outlined with white lines.