NIKOLAEVA PATERA IN ASTERIA REGIO ON VENUS: A SMALL CORONA AT JUNCTION OFTWO REGIONAL FAULT BELTS. G. A. Burba, Vernadsky Institute of Geochemistry and AnalyticalChemistry, Russia’s Academy of Sciences, 19 Kosygin St., Moscow 119991, Russia <gburba@gmail.com>.

Introduction: A rimmed depression in AsteriaRegio on Venus have been named Nikolaeva Patera.The naming was done in 2005 by the InternationalAstronomical Union in commemoration of Dr. OlgaNikolaeva, Russian planetologist and geochemist.The feature is located within the area of ancient ter-rains, but possess clear signs of younger geologicactivity. It is located at the intersection of the twolong, regional-scale fault belts, one of which is con-nected with the formation of Beta Regio upland.

The name origin: Nikolaeva Patera is namedafter Olga Vladimirovna Nikolaeva (1941–2000),who was a planetologist-geochemist at the Labora-tory of Comparative Planetology, Vernadsky Insti-tute, Russian Academy of Sciences. During 26 yearsshe was involved in the planetary research. Her mainfield was geology and geochemistry of Venus, in-cluding both atmosphere and surface of this planet.Her main results in planetology include: ► development of the engineering model of lunarsoil for the spacecraft design and landing (1974); ► discovering (with Venera 8–14 landers data) thediurnal variation process of the cloud cover of Ve-nus – the geochemical cycle and day-to-night changein thickness of the cloud layer (1976); ► the first (and still the only) in situ measure-ments of the chemical data within the near-surfacelayer of Venus atmosphere, done with “Contrast”geochemical indicator designed and built by Olga(two patents for invention obtained); this indicatorprovided the unique data on the redox (reduction-oxidation) conditions in the layer as close as 15 cmfrom the planet’s superheated surface (Venera-13and Venera-14 landers, 1982); ► estimations of terrestrial counterparts for thetypes of Venus rocks after their natural radioactiveelements K, U and Th content (1982, 1997); ► development of geochemical aspects of Venusgeology in application for the layered rocks origin(lava emplacement vs. sedimentation) – after theVenera landers’ close-up panoramic images (1983); ► definition of arachnoids as the specific class ofendogenic geologic structures after the Venera-15and Venera-16 SAR images (1986); ► definition of geochemical uniqueness of therock type at Venera-8 landing site as Na-alkalinesyenites (1983), which proposed as evidence of acontinental crust on Venus (1990), and pancakedomes suggested as source of such rocks (1992). The naming of feature on Venus after OlgaNikolaeva have been done on the proposal of Prof.V.I. Feldman (Geological Department, LomonosovMoscow State University).

Fig. 1. Side-looking radar image of NikolaevaPatera 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 terraininto separate patches (T). Lobate flows (L) run SEoutwards the Patera rim (black line). White sinuouslines are narrow trenches within the fault belts. Lineswith black dots – wide trenches with flat bottom.White circles – “pancake” domes (volcanoes).

NIKOLAEVA PATERA ON VENUS: G. A. Burba

Geographic description: Nikolaeva Patera islocated NW of Beta Regio within the northern partof Asteria Regio. The center of patera is at 33.8°Nlatitude and 267.5°E longitude. As a whole thispatera have an elongated shape with long axis 100km and short axis 60 km. The feature consists ofthree oval-shaped depressions, which are nestedwithin the joint rim (Fig. 1). Elongation is in NE –SW direction, which is along the same way as thenarrow trenches of Agrona Linea fault belt (labeledA on Fig. 2). Nikolaeva Patera marks the SW end ofthis belt. Agrona Linea fault belt could be clearlytraced from Nikolaeva Patera for 2300 km to the NE,then to E and SE around the northern outhills of BetaRegio upland. Patches of Sudenitsa Tesserae sur-round Nikolaeva Patera from every quarter.

Geological setting: Most ancient terrains in thevicinity of Nikolaeva Patera are patches of tessera –bright rugged areas located higher than dark plainterrains (Fig. 3). The latter are next in age. Darkplains fill the areas between tessara patches, embay-ing tessera. These plains in some areas undergone atectonic reworking with numerous narrow sinuoustrenches, which form elongated fault belts. The beltsare younger in age than the dark plain areas. Thereare two main fault belts in the area. One of themhave NE–SW direction and its segment located NEfrom Nikolaeva Patera belongs to Agrona Linea,which is circum-Northern Beta Regio fractute zone.Another fault belt in the area have NW–SE directionwith further changing its running to E (Fig. 4).

There are clear evidences of volcanic activitywithin Nikolaeva Patera and in the area adjusent toits rim. Small domes, both conical and flat-topped(“pancake”), are on patera bottom and on its rim. Tothe SE of patera there is a plain area with lobateflows running radial outwards the patera (Fig. 2).They looks to be originated from the patera’s rim.

Interpretation: Nikolaeva Patera sits at thejunction of the two regional fault belts. Such posi-tion reflects the origin of the patera, which occupiesmost disturbed and so a weak spot of a crust in thearea, being at the intersection of the two zones ofdisturbation, marked on the surface with numeroustrenches. These trenches should resulted from theextension of the planetary crust. The NE – SW beltposition is concentric to Beta Regio. So, the uprisingof Beta Regio upland could be a cause for the for-mation of this belt.

The weak spot of a crust provided a channel forthe interior material upwelling, which resulted involcanic activity and formation of the rimmed de-pression of Nikolaeva Patera. As a whole NikolaevaPatera looks like a small corona-type feature.

Fig. 3. Asteria Regio area radar image. Areasize is 1500 x 1700 km. SAR image: Magellan/NASA.

Fig. 4. Interpretation of regional linear featuresin Asteria Regio. Nikolaeva Patera is located at thejunction of the two regional fault belts. The bordersof these belts are outlined with white lines.