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The surface environment of early Mars had an active hydrologic cycle, including flowing liquid water that carved river valleys.sup.1-3 and filled lake basins.sup.4-6. Over 200 of these lake basins filled with sufficient water to breach the confining topography.sup.4,6, causing catastrophic flooding and incision of outlet canyons.sup.7-10. Much past work has recognized the local importance of lake breach floods on Mars for rapidly incising large valleys.sup.7-12; however, on a global scale, valley systems have often been interpreted as recording more persistent fluvial erosion linked to a distributed Martian hydrologic cycle.sup.1-3,13-16. Here, we demonstrate the global importance of lake breach flooding, and find that it was responsible for eroding at least 24% of the volume of incised valleys on early Mars, despite representing only approximately 3% of total valley length. We conclude that lake breach floods were a major geomorphic process responsible for valley incision on early Mars, which in turn influenced the topographic form of many Martian valley systems and the broader landscape evolution of the cratered highlands. Our results indicate that the importance of lake breach floods should be considered when reconstructing the formative conditions for Martian valley systems. Lake breach flooding rapidly eroded almost a quarter of the volume of incised valleys on early Mars, influencing the topography of the wider Martian landscape., Author(s): Timothy A. Goudge [sup.1] [sup.2] [sup.3] , Alexander M. Morgan [sup.4] [sup.5] , Gaia Stucky de Quay [sup.1] [sup.2] , Caleb I. Fassett [sup.6] Author Affiliations: (1) Department of [...]

Behavioural thermoregulation is a survival strategy that occurs in response to an exceedance of thermal stress‐inducing thresholds. When salmonids experience exceedance of these thresholds, they seek regions of colder water, known as thermal refuges. During an extreme temperature event of summer 2021 (main stem ~31.5°C) a large aggregation of Atlantic salmon (Salmo salar—all age classes) and brook trout (Salvelinus fontinalis—>20 cm) was observed on the Little Southwest Miramichi River in New Brunswick, Canada. Using a drone‐mounted thermal infrared (TIR) sensor, fine‐scale TIR imagery of the occupied refuge was acquired. Polarized glasses were worn by an onshore observer to make visual observations. Constructing maps from these data we examined the spatial distribution of fish, and the corresponding temperature of the areas they occupied. Salmonids were found to be distributed by age class and species, with the distribution driven by the mosaic of temperatures in the refuge. Young of the year (YOY), 1+, 2+ and adult Atlantic salmon occupied areas with average temperatures ~30.1, 28.8, 25.7 and 21.9°C, respectively; whilst mature brook trout occupied areas ~21.8°C. Noteworthy is the observation of thermally aggregating young of the year Atlantic salmon, and the range in temperatures they occupied (~8°C). One isolated, shallow, cold water patch (~22°C) exclusively held YOY Atlantic salmon. Our findings highlight the importance of several different thermal characteristics of thermal refuges and their link to salmonid occupancy and can aid the design of ecologically meaningful thermal refuge augmentation/restoration projects. [ABSTRACT FROM AUTHOR]

Lower-extremity musculoskeletal injuries are common in sports such as basketball and soccer. Athletes competing in sports of this nature must maneuver in response to the actions of their teammates, opponents, etc. This limits their ability to preplan movements. The purpose of this study was to compare impact accelerations during preplanned versus unplanned lateral cutting. A total of 30 subjects (15 males and 15 females) performed preplanned and unplanned cuts while the authors analyzed impact accelerations using an accelerometer secured to their tibia. For the preplanned condition, subjects were aware of the movement to perform before initiating a trial. For the unplanned condition, subjects initiated their movement and then reacted to the illumination of one of 3 visual stimuli which dictated whether they would cut, land, or land-and-jump. A mixed-model analysis of variance with a between factor of sex (male and female) and a within factor of condition (preplanned and unplanned) was used to analyze the magnitude and variability of the impact accelerations for the cutting trials. Both males and females demonstrated higher impact accelerations (P =.01) and a trend toward greater intertrial variability (P =.07) for the unplanned cutting trials (vs preplanned cuts). Unplanned cutting may place greater demands on the musculoskeletal system. [ABSTRACT FROM AUTHOR]

We present an inventory of alluvial fans and deltas within martian impact craters based on a systematic global survey of Context Camera images. Our database includes 314 fan‐hosting craters, with a total of 890 alluvial fans and 114 deltas. Alluvial fans and deltas are more widespread than previously reported (∼40°N to 54°S) and are strongly banded with respect to latitude. Most craters with alluvial fans occur at higher elevations (10°S–30°S) and along the dichotomy boundary (0°–10°N). Deltas occur at lower elevations (0°–40°N) where access to groundwater may have enabled the formation of lakes, and to a lesser extent in the highlands (0°–30°S). Alluvial fans in southern mid‐latitude craters preferentially formed along the northern and southern walls, which may reflect climatic control through solar insolation. The widespread distribution within the observed latitude bands and the similar Hesperian to Amazonian age of alluvial fan‐hosting craters is consistent with late‐stage synoptic precipitation. Plain Language Summary: Martian alluvial fans and deltas are intriguing features because they provide evidence for surface water and a climate that was very different than the present‐day conditions. This study presents a planet‐wide catalog of craters that host alluvial fans and interpreted deltas to understand where and when they formed. We systematically searched images from the Context Camera because this data set has the necessary resolution and coverage to identify and classify the landforms of interest. Our inventory of 314 craters with 890 alluvial fans and 114 deltas shows that these landforms are more numerous and widespread than previously reported. The similar age and distribution of craters with alluvial fans in the southern mid‐latitudes is consistent with a late occurring, widespread (rather than local) source of water. Craters with deltas are preferentially located at lower elevations where interactions with groundwater may have enabled the formation and persistence of lakes. Key Points: Craters with alluvial fans and scarp‐fronted fans (putative deltas) are more numerous than previously reportedThe widespread distribution of craters with alluvial fans in observed latitude bands is consistent with late synoptic precipitationFormation of alluvial fans in southern mid‐latitude craters on northern and southern walls may be influenced by solar insolation patterns [ABSTRACT FROM AUTHOR]

Estimates of river paleodischarges have been used to constrain the former climate of Mars. Paleodischarge has been calculated using mechanistic approximations of the channel bed‐shear stress at the threshold of particle motion or correlative width‐discharge relations derived from empirical terrestrial hydraulic geometry data. We apply both these methods to a study set of gaged terrestrial rivers with field‐measured bankfull properties to assess the reliability of discharge estimates given similar uncertainties as ancient martian rivers. We find that the threshold method yields conservative values, provided a reasonable grain size is used. However, we find that digital elevation models of a similar resolution to those constructed from Context Camera (CTX) data may not be of sufficient resolution to be useful for estimating paleohydrologic conditions. Results from our analysis demonstrate the inherent uncertainties when approximating paleodischarges on Mars and stress the need to consider realistic boundary conditions when determining such values. Plain Language Summary: The amount of water, or discharge, that flowed through martian rivers can be used to understand the planet's former climate. Various methods have been used by researchers to estimate martian river discharge, including relating river width to discharge or calculating the water volume required to move sediment in the river, but it is uncertain which of these provide more accurate results. We applied these same methods to rivers on Earth that have field‐assessed flow rates. We find that using grain size yields conservative discharge values, which is generally more desirable, but that there is significant uncertainty associated with both methods. Key Points: Two methods of estimating martian paleoriver discharge are applied to terrestrial rivers with known bankfull dischargesThe threshold approach yields more conservative discharges when used with realistic grain sizes and high‐resolution topographic dataUncertainties inherent in both methods emphasize the need to consider realistic boundary conditions when applied to Mars [ABSTRACT FROM AUTHOR]

The article discusses that Early Mars had rivers, but the cause of Mars's wet-to-dry transition remains unknown. Past climate on Mars can be probed using the spatial distribution of climate-sensitive landforms. The research was conducted on waterworked landforms and identified changes in the spatial distribution of rivers over time.

The purpose of this study was to determine the association between hip strength and lower extremity kinematics and kinetics during unanticipated single-leg landing and cutting tasks in collegiate female soccer players. Twenty-three National Collegiate Athletic Association division I female soccer players were recruited for strength testing and biomechanical analysis. Maximal isometric hip abduction and external rotation strength were measured using a hand-held dynamometer and expressed as muscle torque (force × femoral length) and normalized to body weight. Three-dimensional lower extremity kinematics and kinetics were assessed with motion analysis and force plates, and an inverse dynamics approach was used to calculate net internal joint moments that were normalized to body weight. Greater hip external rotator strength was significantly associated with greater peak hip external rotation moments (r = 0.47; p = 0.021), greater peak knee internal rotation moments (r = 0.41; p = 0.048), greater hip frontal plane excursion (r = 0.49; p = 0.017), and less knee transverse plane excursion (r = -0.56; p = 0.004) during unanticipated single-leg landing and cutting tasks. In addition, a statistical trend was detected between hip external rotator strength and peak hip frontal plane moments (r = 0.39; p = 0.06). The results suggest that females with greater hip external rotator strength demonstrate better dynamic control of the lower extremity during unanticipated single-leg landing and cutting tasks and provide further support for the link between hip strength and lower extremity landing mechanics.