J. Raitala

University of Oulu · Department of Physics

Hypervelocity impacts occur on bodies throughout our solar system, and play an important role in altering the mineralogy, texture, and magnetic properties in target rocks at nanometer to planetary scales. Here we present the results of hypervelocity impact experiments conducted using a two-stage light-gas gun with 5 mm spherical copper projectiles...

The large scale outflow channels of the Hellas impact basin are characteristic to its eastern rim region. Although the majority of the valles are located in the large-scale topographic trough connecting Hesperia Planum and Hellas basin, the most far-reaching of them, Reull Vallis is situated to the south-southeast of this trough cutting through Pro...

The Chelyabinsk meteorite (which fell on February 15, 2013) is a LL5 chondrite of shock stage S4, whose fragments are classified into light and dark lithologies. According to the intensity of their shock metamorphism, light lithology fragments are subdivided into two groups, which were affected by peak pressures within the ranges of 20-25 and 25-30...

The work outlines the history of geologic activity within Harmakhis Vallis based on the mapping and dating results of high-resolution CTX and HiRISE images.

The work outlines our results of mapping and dating on the Harmakhis Vallis channel. We focus especially on the possible ice-facilitated flow features which cover the channel floor, and investigate when the processes that formed these units occurred.

In this study, we outline our results of mapping and dating the geologic activity on the Harmakhis Vallis floor. We focus especially on the large-scale flow units which are possibly ice-facilitated and cover the channel floor almost entirely, and investigate when the processes that formed these units occurred.

The CTX and HiRISE data-based work gathers the observations of water and ice influence on the Harmakhis Vallis region on Mars.

This paper presents morphometric parameters of Martian layered sequences of different origin that outcrop in the scarps and crater walls, which form natural geologic profiles. The objective of this study was to develop quantitative criteria that would allow distinguishing layers of volcanic and, presumably, sedimentary origin. As a result of measur...

Regional tectonic time span extends from 4-Ga-old highland to <3-Ga-old hanging wall faults and to Claritas Rupes activity 2.5 Ga ago.

CTX, HiRISE, and HRSC data was used to constrain the formation time of two martian outflow channels, Waikato and Reull Vallis, to a period between 3.52 and 3.67 Ga.

Practically all of the examined spherules extracted in 1948–1949 from soil at the crater field of the 1947 Sikhote Alin meteorite shower are ablation spherules produced during this meteorite fall. The spherules can classified into two textural types: (i) fine-grained, which consist of Ni-bearing magnetite (3–6 wt % NiO) dendrites, sometimes with mi...

Layers exposed in volcanic and sedimentary key sites were used as a foundation for morphologic and morphometric identification criteria. Criteria were used for several test sites and results compared to determine the origin of the observed layering.

Observing locations, structures, and positions of the Hellas floor ovals, depth of the ovals can be estimated. This information may be used to determine the formation mechanisms of the oval structures.

We report textures, mineralogy, and compositions of the meteorite ablation spherules collected at the crater field of the Sikhote-Alin iron shower. Using specific features of the spherules we give constraints on formation parameters of the spherules.

Existence of glacial-like formations on the southern mid-latitude highland of Claritas Fossae is postulated and will be presented with details.

We were able to find new age constraints for the upper parts of this system through crater size-frequency distributions using the available images of CTX, HiRISE and HRSC and compared them with the previous results from MDIM images [2]. We also mapped the Morpheos basin depression and the confining region in CTX resolution.

The study is a detailed look on one of the several fluvial systems located on the eastern rim region of the Hellas basin on Mars. We analyzed the morphologic and morphometric characteristics of an extensive channel system, which extends for over 650km from 35.8°S, 106.4°E in Hesperia Planum to Reull Vallis at 39.5°S, 98.1°E, and has a drainage area...

Soil layers at the Tunguska event site may have accumulated infalling extraterrestrial matter derived from the Tunguska Cosmic Body (TCB). Using mineralogical, textural, and chemical criteria, a set of metal and silicate spherules of probably cosmic origin was identified in the collection of spherules and rounded particles recovered from sites with...

A marker layer divides stratified blocks on the floor of Ius Chasma into light-gray and darker-gray units with numerous cross-cutting strike-slip faults. The blocks probably originated from the rim of Ius Chasma.

We investigated particles that were found in products from high-velocity shock experiments with peak shock pressures up to 115 GPa. Texturally, the particles are similar to lunar agglutinates. The particles have specific magnetic characteristics.

Abstract– A large number of micrometeorites (MMs) was recovered from glacier deposits located at the north-eastern passive margin of the Novaya Zemlya glacier sheet. Melted, scoriaceous, and unmelted micrometeorites (UMMs) are present. Unmelted micrometeorites are dominated mostly by chondritic matter, but also a few achondritic MMs are present. He...

Impact crater formation is sometimes affected by preexisting target inhomogeneities like faults or joint sets in ways that cause the plan view of the crater to deviate from the idealized circular shape. The resulting polygonal impact craters have been known to exist on the Moon for over a century, and they have been subsequently identified on all t...

Four prominent fluvial systems, Dao, Niger, and Harmakhis Valles, and a system of smaller channels between Niger and Harmakhis Valles characterize a wide topographic trough that connects Hesperia Planum and Hellas Planitia (Hesperia–Hellas trough, HHT). The source depressions of the canyons of Dao and Harmakhis Valles are at the lowermost level (ab...

We used Thermal Emission Spectrometer (TES), Thermal Emission Imaging System (THEMIS), High-Resolution Stereo Camera (HRSC), and Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) data to assess the physical and compositional properties of the Malea Planum portion of the Circum-Hellas Volcanic Province (CHVP). Our analysis of...

The eastern Hellas basin rim has been highly modified by a multitude of both volcanic and fluvial processes. It is covered by a large part of the Circum-Hellas Volcanic Province, consisting of the volcanic plains of Hesperia Planum and western Promethei Terra, as well as the two central volcanoes Hadriaca and Tyrrhena Patera and their associated la...

Wrinkle-ridged plains, common on the terrestrial planets, are inferred to form by tectonic deformation of volcanic or sedimentary surfaces. If wrinkle-ridged plains adjacent to volcanic features originated from volcanic activity associated with the features, then the plains should have similar ages to the volcanic features, as well as other morphol...

Geologic evolution of the western portion of Promethei Terra (40–50°S, 90–105°E) consists of two major episodes. The first was the formation of a late Noachian–early Hesperian volcanic province. During this episode a kilometer-thick suite (≈0.3 × 106 km3) of lavas accumulated to the south of Reull and Harmakhis Valles within a regional depression t...

The deposition of ice-bearing materials at different levels during the growth of the lava plateau in Hesperia-Hellas Trough offers a better explanation to the key features of the Valles structures.

In a crater on Noachis Terra there are domes within a narrow crater floor unit. The unit is connected to a channel that breaches the crater rim. In this study we discuss of a possible pingo-like characteristics of the domes.

The first results of a systematic photogeological study to look at the characteristic morphology of the layers formed by volcanic processes (especially emplacement of lava flows) and due to deposition and sedimentation on Mars.

Pre-impact inhomogeneities of the target material sometimes cause the rim of an impact crater to be composed of several straight segments, instead of being circular. The venusian surface hosts 121 such polygonal impact craters (PICs)>12 km in diameter. Their straight rim segments are often parallel to the orientations of the surrounding tectonic st...

In our study we have analyzed 1) the head regions of the Hellas region outflow channels and related structures, and 2) the morphologic and morphometric characteristics of one of the channel systems within the Hellas rim region. We have found that ice-deposits are important as primary sources (both sub-and on-surface) for the different scale systems...

In order to assess the age relations between astra/novae (features with extensive radial fracture-graben systems) and their surroundings, and to determine the duration of their activity, we undertook a photogeologic analysis of Magellan images of 78 astra, 49 dark-parabola craters and 114 clear-halo craters. For seven of these 78 astra it was found...

Building on previous studies of volcanoes around the Hellas basin with new studies of imaging (High-Resolution Stereo Camera (HRSC), Thermal Emission Imaging System (THEMIS), Mars Orbiter Camera (MOC), High-Resolution Imaging Science Experiment (HiRISE), Context Imager (CTX)), multispectral (HRSC, Observatoire pour la Minéralogie, l’Eau, les Glaces...

We constructed THEMIS daytime-infrared mosaics (spatial resolution 100 m/pixel) of several regions of wrinkle-ridged plains bounding the Circum-Hellas Volcanic Province (CHVP), and performed crater counts to assess whether these plains were associated with volcanism in the CHVP. We determined cratering model formation ages of 3.4-3.7 Ga for SE Male...

We discuss new analyses for terrain in and around the Circum-Hellas Volcanic Province on Mars, providing new estimates of size and age of the province, and information on its physical-compositional properties.

Layered blocks on the floor of Ius Chasma provide tectonics, cross-cuts and insights into the development, materials, layering, strata forming events and early geology on the tableland surrounding Ius.

The eastern Hellas Basin rim region displays evidence for continued fluvial and glacial activity from Noachian-early Hesperian to Amazonian. The observations and analysis of the region suggest a complex and multitemporal fluvial activity.

We present evidence for extensive dike systems on the Hadriaca Patera volcano on the east Hellas rim and in the volcanic plains south of it, near the outflow channels, and hypothesise on what controls their distribution and orientation.

We report on the texture and mineralogy of two FeNi metal and one metal-chromite particles, which possibly are the first unmelted metal micrometeorites found so far.

In the representative sample of coronae of Venus (55 coronae) we have found six coronae whose activity lasted for several hundred million years. Four of them which, represent the evolution of individual mantle plumes have astrum-like components.

This study focuses on one of the several fluvial systems located on the eastern rim region of the Hellas basin, Mars. We have analyzed the morphologic and morphometric characteristics of this extensive, over 650km long channel system. Beginning from Hesperia Planum, it intersects several basins and exhibits a multitude of flow morphologies. Eventua...

We used Mars Express High Resolution Stereo Camera images of the Tyrrhena Patera volcano to assign cratering model ages to material units defined in the Viking Orbiter-based geologic mapping. Cratering model ages are generally consistent with their stratigraphy. We can identify three key intervals of major activity at Tyrrhena Patera: (1) formation...

Impact craters are not always circular; sometimes their rims are composed of several straight segments. Such polygonal impact craters (PICs) are controlled by pre-existing target structures, mainly faults or other similar planes of weakness. In the Argyre region, Mars, PICs comprise ˜17% of the total impact crater population (>7 km in diameter), an...

Polygonal impact craters (PICs) can be used to decipher tectonics of a cratered surface (1-4). Studies of PICs on Mars and Venus (5-7) have provided information of their importance in revealing ancient structures. Some observations are not fully explained with the current ideas. Thus, new ideas for the PIC formation type and preferred PIC size are...

Abstract The Hadriaca Patera (HP) volcano [e.g. 1-9] on Mars is situated on the north-easten rim of the giant Hellas impact basin, and on the western edge of the vast volcanic plains of Hesperia Planum [10, 11]. The eastern Hellas rim region harbours also other, possibly separate centers of volcanism that have only recently been proposed [12, 13]....

Building on previous studies of volcanoes around the Hellas basin with new studies of imaging (HRSC, THEMIS, MOC, HiRISE, CTX), multispectral (HRSC, OMEGA), topographic (MOLA) and gravity data, we define a new Martian volcanic province as the Tyrrhena-Malea Volcanic Province (T-MVP). With an area of >2.1 million sq. km, it contains the six oldest c...

Polygonal impact craters may form by thrusting along pre-existing fault planes. They are preferentially formed in the size range of small to mid-sized complex craters, and may perhaps indicate the presence of basin-induced conjugate shear fractures.

The chondritic melt rock NWA 4218 contains within the melt matrix regions rich in an iron phosphate mineral. The hydrous phosphate could be formed either (1) by weathering in an acid environment or (2) by terrestrial alteration of a primary phosphate.

The results of this study indicate that the crater formation process on Venus reflects the existing planes of weakness and/or fractures in the target material.

The analysis of topographic and morphologic characteristics of the head areas of Hellas valles formations gives implications for relative timing of the formation of the sources of the channels, and also for the volcanic episodes within the region.

We search for dike-indicative formations in the region around Hadriaca Patera. So far, we have identified and documented a large number of straight/curvilinear ridges, fractures and grabens on the volcano as well as in its vicinity.

Valley, channel, sapping, alcove, spring, fault and fold structures allow us to find traces of hydrologic history in relation to episodic tectonics and water re-distribution on Mars. Five different water-related phases were identified.

For seven of 78 known astra (novae) it was possible to estimate the duration of their geologic activity from the older phases of their tectonism through their younger ones. It was found that the activity lasted for several hundred million years.

The western Promethei Terra region (36-50°S, 90-106°E) studied is roughly ~700 km across. It occupies a unique area on the smoothened eastern Hellas basin rim, and consists of two parts: a gentler (~0.07°, eastward of ~97°E) and a steeper (~0.88°, W of ~97°E) regional slope. The Noachian cratered terrain surrounds the region in the NE, E, and S. Th...

The eastern rim region of Hellas basin is characterized by the four prominent and quite extensively researched (cf. Crown et al., 2005, and references therein) outflow channels. In this work we focus on the Reull Vallis. On the basis of observations from available data sets, we present a hypothesis for the evolution of Reull Vallis and its complime...

We briefly describe the history of landings on Venus, the acquired geochemical data and their potential petrologic interpretations. We suggest a new approach to Venus landing site selection that would avoid the potential contamination by ejecta from upwind impact craters. We also describe candidate units to be sampled in both in situ measurement an...

High Resolution Stereo Camera (HRSC) images of Hadriaca Patera, Mars, in combination with Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Infrared Imaging System (THEMIS) data sets, reveal morphologic details about this volcano and enable determination of a chronology of the major geologic events through new cratering ag...

It has been proved that the polygonal impact craters (PICs) are found on the Moon, Mercury, Mars and several asteroids and icy moons. Latest studies have shown that they exist also on Venus, even though the polygonal shape is not as well developed as it is on the Moon or Mars. On Mars, the polygonal impact craters - and especially their straight ri...

Polygonal impact craters (PICs) are craters whose shape in plan view is more or less angular instead of being circular or ellipsoidal. This type of craters are present and often common on the Moon, Mercury, Mars and several asteroids and icy moons and after the careful analysis we found on Venus 131 impact craters, which show at least two straight...

On the Venusian surface, there can be found a rather large population of structures with prominent radial features. The term “nova” or “astrum/astra” are used to describe this special group of volcanotectonic structures with a stellate fracture pattern radiating around a central summit or fracture. In this paper, we studied the distribution and cha...

We have analyzed the topographic and morphologic characteristics of the 62 multiple coronae [1,2,3] on the surface of Venus in order to assess their possible formation models.We have evaluated the following models: 1) Movement of the lithosphere over a stationary mantle plume [4, 5]. 2) Migration of a mantle plume or diapir under the lithosphere [4...

These mesas show evidence of intense degradation/erosion. They are the source of several fluvial channels, which have been active during a long period of time. We interpret the mesas as possible remnants of an ancient larger glacier-like structure.

Analysis of three martian paleolakes and connecting channels in Promethei Terra.

We present a preliminary view of the possible evolution of the smooth plains region near Promethei Terra, and characterize the features found within the region.

There are several formation models for the multiple coronae of Venus in the framework of the mantle diapir model. We attempt to constrain these models for multiple coronae and also to establish age relationships between their component structures.

Most of venusian coronae have an elliptical shape which reflects the tectonics of the area they are located in.

This study showed that there are polygonal-shaped impact craters on Venus and they do show some correlations with local tectonics and that the diameter affects their abundance.

The last major geological episode of the study region (35°-45°S, 90°-110°E) was a period of late resurfacing. Localised channels (with no apparent sources), possible lag deposits, and esker-like features imply that one possibility for this was a glacier.

The focus of the study is a highly modified crater in Arabia Terra, Mars. It has undergone complex post-formation evolution and there is multitude of evidence of water-related processes.

The identified rotational fault component allows estimations of the block fracturing and further discussions of the origin, re-location, and thickness of the block.

The slope between Reull-Teviot Vallis and Hellas basin has a set of unique flat-topped E-W elongated mesas with scalloped flanks. They show evidence of long-lasting intense erosion, indicating that they are remnants of a large regional massif.

A geologic analysis of 274 images acquired by the high-resolution MOC camera onboard the Mars Global Surveyor spacecraft within the Arabia Terra low neutron flux anomaly (which is indicative of an anomalously high abundance of hydrogen: up to 16 wt % of the equivalent amount of water) was performed. Correlation between the enhanced abundance of equ...

Impact craters with fractured floors are a feature found on many terrestrial planets. On the Moon they typically occur in near-mare craters, and are thought to be caused by laccolith etc. intrusions ascending and progressing through the under-crater fracture systems [e.g. Schultz, 1976]. The floor-fractured craters on Mars exhibit a wide range of t...

Abstract— Impact craters that in plan view are distinctly polygonal rather than circular or elliptical are common on Mars and other planets (Öhman et al. 2005). Their actual formation mechanism, however, is somewhat debatable. We studied the polygonal craters of different degradational stages in the region of the Argyre impact basin, Mars. The resu...

Pre-Cambrian shields and platforms occupy a large part of the Earth's continental surface. The crystalline rocks of these megastructures are the result of intense metamorphic, igneous and tectonic transformations. It is often difficult to recognize evidence of the past sedimentary, volcanic and igneous activities here. Even more problematic is the...

The channel out of the Claritas paleolake led out water and deposited particles. Dust was washed away, particles were sorted and re-oriented. The alluvial fan can be identified by four-channel HRSC classification.

According to the preliminary study, Noachis Terra has been modified by several processes, which have characterized the unforeseeably varied geological history of the region.

The melt rocks of the meteorite craters in central Finland are enriched in siderophile elements and other meteoritic components. Sulphides in the impact melt rocks are main carriers of siderophile elements, especially for Ni and Co.

On Mars craters with floor fractured and/or irregular depressions are linked to specific locations near the dichotomy boundary and giant impact basins. They provide information on the subsurface processes.

Surface physical properties derived from HRSC multi-angular observations are determined and mapped for different units (volcanic plains, wrinkled terrains and dark wind streaks) present on the northern part of Gusev and to the north, toward Apollinaris Patera.

Floor-fractured craters appear to occur on all the cratered terrestrial planets. Their floors are typically raised as a whole, or they are cut into large elevated blocks. The floors exhibit radial, concentric and/or polygonal fractures, occasionally mixed with volcanic features. The craters occur almost always next to large regional volcanic provin...