Search

The Navua Valles are comprised of a system of channels and valleys on the inner Northeastern rim of Hellas Basin, which is a 1500-km-long sloping terrain. Drainage systems and regional geology in this unique setting were not previously mapped in detail. We mapped this region using CTX (6 m/px) as the base map and assessed surface unit ages resulting from our crater counting. We found that the timing of the deposit-forming episodes in this region during the Hesperian and Early to Middle Amazonian largely correlated to active phases of the Hadriacus Mons volcanic center. We found evidence for several episodes of fluvial activity Hesperian to the Amazonian with declining intensity, and transitioning to ice-dominated processes. The channels in the Navua Valles region erode into deposits dating from the Noachian to Early Amazonian, including the Noachian highlands, Noachian to early Amazonian crater ejecta, and likely volcanic plains formed from the Hesperian to the Hesperian–Amazonian transition. Channels directly originating from Hadriacus Mons are younger, while precipitation-fed channels at larger distance from the volcanic center are older, indicating different triggers for fluvial activity. Crater counting results indicate that almost all channel floors were at least partially resurfaced during the Amazonian and that several channel deposits formed during the last 0.5 Gyr. Water pathways likely included surface channels, lakes, and subsurface flow. The Navua Valles channel system is discontinuous, and the number of terminal deposits (sink locations) is almost as high as the number of channel sources, which is unusual for valley networks elsewhere on Mars. Interior channels formed only in the major Navua channels, they are even more fragmented than their parent channels, but occur along their entire length. Channels and valley systems within the Navua Valles are potential targets for in situ astrobiological studies, as they could have provided potential habitats at least periodically, from the Late Hesperian to the Late Amazonian.

Volcanic channels are common features on the terrestrial planets. They have diverse morphologies including sinuous rilles, channelized flows, and potentially collapsed lava tubes. Many of these channels are a part of a typical igneous assemblage of landforms. In addition, some channels have an ambiguous origin, where a volcanic interpretation explains many of the observed features in some settings. This chapter describes volcanically formed sinuous channels, pitted channels, channelized flows, streamlined forms, platy terrain, and discusses a potential volcanic context for outflow channels and some valley networks on Mars.

Channel morphologies are sinuous, negative-relief linear forms that form by a current of water or lava. They may be fluvial or volcanic in origin. Channels are exclusively volcanic on Venus, volcanic or fluvial on Mars and fluvial on Titan. On Venus and Mars, channels are all paleoforms while on Titan (and Earth) they are actively forming. Channels may be hosted by valleys, that represent the cumulative erosional history of the embedded channel. They may be singular or may form braided pattern separated by streamlined island forms (e.g., Kasei Valles); a channel floor may host interior channels (e.g., Navua Valles), and channels may disappear gradually into flat plains (e.g., Simud Vallis). These are just a few of their characteristics that make their cartographic representation a complex issue.In this work we analyzed and compared the symbology of channel forms in planetary geologic maps. An ongoing work on planetary geologic symbology identified 95 maps containing channel symbols in a total of 154 map (Nass et al. 2017b). Symbology is important for several reasons (Nass et al. 2011, Nass et al. 2017a). Although each map is complete on its own, standardized symbology enables direct comparison between maps. Maps are used for measurements: channel morphometry measurements across different quadrangles become problematic if symbols are used and defined differently.Planetary geologic maps use three classes of symbols for representing channel forms: polygons as geologic units, polygons as surficial units laid over a geologic unit and line symbols for smaller channels. Line symbols often transform to geologic units when they reach a cutoff size for the used map scale. Line symbols do not continue over the unit symbols. This way drainage networks are split into two, incompatible symbol types. The cutoff size is often not reported in the legend that use the vague "narrow channels" designation for the line symbols. Sometimes line symbols are used only for "small distributary channels" or "small valleys".Named channel units may be grouped geographically (e.g., Ares Vallis), by age (e.g., Hesperian channels), by morphology (steep walled channels), process (outflow channels) or as true geologic units (vallis floor sediments). These categories may be even mixed within one map.The line symbols are typically solid blue (cyan) lines. This is in accordance with FGDC standards (FGDC 2006).Different problems arise with drainage databases (Hynek et al. 2010, Alemanno et al. 2018). They typically uniformly trace dendritic valley networks, but they also contain singular and other channel forms, whereas "outflow channels" and lava channels are missing from these databases. The global map of Tanaka et al. (2014) uses two different blue line symbols for "channel axis" (i.e., valley network and some outflow-like channels) and "outflow channels".It is needed to redefine channel form classification in the planetary domain and symbology (from Venus to Mars to Titan) and make it clear for mappers if different symbols should be used for different sizes, origins, and morphologies and how different symbols may be combined in one map.

The Navua Valles are a system of channels and valleys on the inner rim of Hellas Basin. The aim of this mapping study was to determine the geologic history of the Navua Valles region; and the relationships between the basement, flow, and channel units along the northeastern slope of Hellas Basin. We have produced a 1:1 million scale geologic map of the Navua Valles region, utilizing standard USGS geologic mapping procedures, but not within a regular USGS mapping project. We selected the mapping area boundaries specifically to cover the Navua Valles drainage systems. The primary base of this mapping effort was a mosaic of 161 Mars Reconnaissance Orbiter Context Camera images, at approximately 6 m/pixel. This paper is part of a double publication, one paper describing the geology of this area, and this paper presenting the geologic map produced during the investigation.

The Navua Valles are systems of paleodrainages located north of Dao Vallis, which empty into Hellas Planitia, the largest impact basin on Mars. In this study, we mapped and characterized the Navua Valles Region's individual drainage systems, including drainages along the southwestern flank of Hadriacus Mons, and one valley network from the same source as Navua Valles but flowing in the opposite direction. The major drainage systems share morphological characteristics common to both outflow channels and valley networks. The slopes in this region are dissected by two major Navua drainage systems (here Navua A* and B*) and several shorter, sub-parallel valleys formed on the highest gradient (approximately 20 m/km [1.15°]) slopes, at the lowest part of Hellas Basin's rim. The two major drainage systems originate in the highlands, and empty into the basin. Our mapping suggests that water in Navua Valles reached the basin floor in a complicated descent and included several episodes of surface ponding, surface runoff, infiltration, subsurface flow and subsequent outflow. The most prominent channel system, Navua A, forms a repetitive sequence of deep incision into bedrock, followed by a transition into broad channels in erodible materials, and then into unconfined deposits. This successive erosion–transport–deposition sequence continues to repeat along the valley's entire length forming a discontinuous pattern that is consistent with classical fluvial process models. The channels cut into volcanic plains likely emplaced from the formation of Tyrrhenus and Hadriacus Montes. The dendritic source valleys of Navua A originate from the rim of a highland crater while the rest of this subsystem consists of a single, discontinuous channel which is consistent with a single water source zone that likely supplied water for all channels downslope. These drainages may have formed as discontinuous channels, revealing the potential existence of subsurface drainage pathways located within an approximately 1.5 × 10 5 km 2 area. Water transported underground emerged in segments that are either isolated or aligned downslope from each other. We have identified several causes of discontinuities, located the zones of potential ground-water discharge and recharge, and a site of localized precipitation at the headwaters of Navua A.

Elevation data can characterize geology, from global to local scales. For centuries, however, the only planetary topographic data were those of lunar peaks and craters. In the last few decades, several independent techniques have been developed to extract topographic information from diverse types of planetary datasets, which provide key information for the distinction and geologic interpretation of surface features. In this chapter, we discuss techniques to obtain, reconstruct, and visualize elevation data.

The slopes of northeastern Hellas Basin, Mars exhibit a wide variety of fluvial landforms. In addition to the Dao-Niger-Harmakhis-Reull Valles outflow channels, many smaller channels and valleys cut into this terrain, several of which include discontinuous sections. We have mapped these channels and channel-associated depressions to investigate potential paleolakes from the Navua Valles in the West, through the Hadriacus Mons volcano in the center, to the Ausonia Montes in the East. We have identified three groups of candidate paleolakes at the source regions of major drainages and a fourth paleolake type scattered along the lower reaches of these drainages. Each paleolake group has a distinct character, determined by different formative processes, including precipitation and groundwater for lakes at the channel sources, and fluvially transported water at the lower channel reaches. Only one of these 34 basins had been cataloged previously in paleolake basin databases. Several of these sites are at proximity to the Hadriacus volcanic center, where active dikes during the Hesperian could have produced hydrothermal systems and habitable environments. Deposits within these paleolake depressions and at the termini of channels connected to these candidate paleolakes contain the geological and potentially biological record of these environments.

We mapped the northwestern Tharsis region to the east of Olympus Mons and described three distinct channel-and-island morphologies within three channel groups. Islands include irregular and streamlined islands in both lava flows and fluvial systems and residual islands in collapsed systems. We interpret these channels to have formed by a combination of tectonic, collapse, lava, and fluvial (hydrothermal) processes, which produced fissures, pits, flows, and channels with streamlined islands, respectively. This formation model is consistent with the traditional model of Martian fossae-sourced channel systems, where both lava and water were transported along these same channels, in some cases multiple times forming potential habitats. We also considered a lava flow formation model for the observed features. We determined the approximate age of the channel-forming activity to be Late Amazonian, contemporaneous with other, distinctly lava flow processes in the Tharsis region.

Reference surfaces, coordinate systems and projections are the prerequisites for the geospatial analysis of planetary surfaces. In the followings we discuss how these parameters are defined and used on different types of planetary bodies, including rocky planets, satellites, irregular bodies and gas giants.

We studied optical microscopic and micro-Raman spectroscopic signatures of shocked olivine from the ALH 77005 Martian meteorite sample. The purpose of this study is to document pressure and temperature-related effects in olivine over the entire sample, which can aid in understanding structural changes due to shock metamorphism and the post-shock thermal annealing processes of lherzolitic Martian meteorites. According to the optical microscope observations, three areas may be discernible in olivine of the ALH 77005 in the vicinity of the melt pocket. The first area is the thermally undisturbed part of a grain, which contains a high density of shock-induced planar microdeformations such as Planar Deformation Features (PDFs) and Planar Fractures (PFs). Compared to the first area, the second area shows less shock-induced microstructures, while the third area is a strongly recrystallized region, but not formed from a melt. A common Raman spectral feature of these olivines is a regular doublet peak cen...

(1) A network of subsurface wedges that are composed of a mixture of ice and sand or rubble. Ice and sand layers may alternate within a wedge (Berg and Black 1966). They can be distinguished from other composition wedges by the presence of accessory landforms, such as gullies. (2) A frost-fissure polygon net showing evidence of both primary and secondary filling: ▶ sandwedge polygon (Harris et al. 1988 and references therein).

To search for local and global scale geologic associations that may be related to the internal dynamics of Io, we have completed a global catalog of all mountains and volcanic centers. We have identified 115 mountain structures (covering approx. 3% of the surface) and 541 volcanic centers, including paterae (calderas and dark spots) and shield volcanoes. The average length of an Ionian mountain is 157 km, with the longest being 570 km. The mean height of Ionian mountains is 6.3 km, and the highest known mountain is Boosaule Montes (17.5 +/- 3 km). Five basic morphologic types of mountains have been identified; mesa, plateau peak, ridge, and massif. Very few mountains bear any physical similarity. to classic volcanic landforms, but many resemble flatiron mountains on Earth and are interpreted as tilted crustal blocks. This would be consistent with the hypothesis that most mountains are thrust blocks formed as a result of compressive stresses built up in the lower crust due to the global subsidence of volcanic layers as they are buried over time. More than one mechanism may be responsible for all Ionian mountains, however. The proximity of some mountains to paterae may indicate a direct link between some mountains and volcanism, although it is not always clear which came first. In contrast to earlier studies, a pronounced bimodal pattern is observed in the global distribution of both mountains and volcanic centers. The regions of highest areal densities of volcanic centers are near the sub- and anti-Jovian regions, but are offset roughly 90deg in longitude from the two, regions of greatest concentration of mountains. This anticorrelation may indicate the overprinting of a second stress field on the global compressive stresses due to subsidence. The bimodal distribution of volcanic centers and mountains is consistent with models of asthenospheric tidal heating and internal convection developed by Tackley et al.Over regions of mantle upwelling, compressive stresses in the lower crust induced by global subsidence might be reduced, encouraging volcanism and discouraging mountain building. In regions of mantle downwelling, these compressive stresses in the lower crust might be increased, discouraging volcanism and encouraging mountain building. Alternatively, the global pattern may be related to possible (but undocumented) nonsynchronous rotation of lo, which would produce two regions each of compression and extension in the crust. Evidence of layering and of mass wasting, including landslides, block sliding, debris aprons and downslope creep, on Ionian mountains suggests that the crust of Io is essentially a layered stack of partially consolidated volcanic lavas and plume deposits, becoming more consolidated with depth. The lower crust especially may also be ductily deformed, punctuated by volcanic intrusions and faulting at paterae, and broken into blocks, some of which have been uplifted to form mountains.

(1) Solifluction-like lobes or small-scale lobes: well-defined lobe or tongue-shaped landform tens to hundreds of meters wide (Johnsson et al. 2012) (1.1) Non-sorted lobes or smooth-textured lobes. Small-scale lobes that show no evidence of a clast-rich lobe front (Johnsson et al. 2012; Fig. 1) (1.2) Sorted lobes or clast-banked lobes. Small-scale lobes that have a distinct front with clasts and relatively few clasts on the tread surface, similar to stone-banked lobes on Earth (Gallagher et al. 2011; Johnsson et al. 2012; Fig. 2)

At the shorelines of several lakes on Titan putative drowned river valleys are seen on radar images (Stofan et al. 2007). Flooded topography is indicative of very low slopes. This morphology suggests drowned coasts. A dendritic network of wide, km-scale valleys ending in Kraken Mare also shows ▶ ria morphology (see image in ▶Valley Network (Titan)). A submerged channel within a flooded valley and a nearby inundated crater form is suggestive of lower liquid levels in the past (Wasiak et al. 2013).

(1) Grounding line wedges or till deltas formed by the deformation of subglacial till (and other sediments) that reach the grounding line. These are fanor wedge-shaped sedimentary units. The mound’s top surface slopes slightly upward in the direction of flow, due to the pressure of the overlying ice shelf (Fig. 1). (2) Grounding line fans form where subglacial meltwater streams discharge subaquatically in a marine environment (Powell 1990). These are also named subaqueous esker deltas or beaded ▶ eskers (McMenamin and McGill 2005). (3) Morainal banks (moraine ridges, DeGeer moraines) formed by various processes, including pushing. They are often asymmetric, straight, or concave in planform.

(1.1) Knobs: small, typically rounded, isolated structures, often with steep slopes (isolated peaks) (Fig. 8/1) (1.2) “Mounds” may refer to any typically round-shaped elevation or may be understood as dome-like elevations. Subdued mounds are characterized by low-angle slopes. (1.2.1) Cones (conical mounds) have a circular to subcircular base that tapers to a (in many cases theoretical) point at the top (the apex – the peak), typically with concave or straight slopes (e.g., Fig. 4/14). (1.2.2) Domes (domical mounds) are circular to elliptical in plan view and have a smoothly rounded summit area and typically convex slopes (e.g., Figs. 1, 3/29, and 4/15). (1.2.3) Shield-like mounds are similar to cones or domes but with a wider base (lower height-to-diameter ratios) (e.g., Fig. 5/24). (1.2.4) Mesas (flat-topped mounds) have flat top and steep slopes and a circular to angular plan view shape. “Pancake-like structures” are usually understood as circular, compositional structures, whereas “mesas” are typically understood as eroded remnants of formerly larger structures. The term “flat-topped mound” has no genetic inferences. Sometimes they are called table mountains (e.g., Figs. 2/10 and 7/22, 31). (2) Raised rim depressions have “closed or mostly closed positive-elevation rims encircling lower elevation terrain” (Burr et al. 2009).

(1) Sorted circles appear as a circular border of clasts surrounding a center of fines. The stony borders show size segregation with the largest clasts at the surface of the border with decreasing size with depth. On horizontal surface they retain their circular shape, but on slopes they become oblong or form stripes. They vary in diameter from a few centimeters to about 4 m. The process of patterned ground formation may create stony areas among the sorted features that act as a trap for airborne fines as well as those produced by in situ weathering. The storage of these fines supplies the material for building the plugs that, intruding gravel beds and reaching the surface, eventually creates sorted circles (Ugolini et al. 2006). Washburn (1997) defines plugs as a commonly vertical subsurface cylinder or more irregular mass of more or less cohesive soil, with or without stones, which extend upward from depth and may or may not reach the surface. The expression of a plug that reaches the surface is a plug circle or related form of patterned ground. (2) Sorted polygons (stone polygons) are patterned ground polygonal forms demarked by a border of stones that limit a central area of fines (Figs. 1, 2, and 3). The stones at the border, the flag stones, are nearly vertical in position. Unlike sorted circles, sorted polygons never develop singly. In the case of inactive polygons on Earth, the stones are covered with lichens, while vascular plants grow between the slabs. They are of variable size from 10 cm to about 10 m. (3) Sorted stripes (on hillslope) (striped ground, striped soil, earth stripe, stone stripes) are features where the pattern is given by parallel alignment of stones and intervening stripes of fines (Figs. 4 and 5). They are reported on slopes with more than 2 –3 gradient (Washburn 1956). Sorted