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The only martian rock samples on Earth are meteorites ejected from the surface of Mars by asteroid impacts. The locations and geological contexts of the launch sites are currently unknown. Determining the impact locations is essential to unravel the relations between the evolution of the martian interior and its surface. Here we adapt a Crater Detection Algorithm that compile a database of 90 million impact craters, allowing to determine the potential launch position of these meteorites through the observation of secondary crater fields. We show that Tooting and 09-000015 craters, both located in the Tharsis volcanic province, are the most likely source of the depleted shergottites ejected 1.1 million year ago. This implies that a major thermal anomaly deeply rooted in the mantle under Tharsis was active over most of the geological history of the planet, and has sampled a depleted mantle, that has retained until recently geochemical signatures of Mars’ early history. The ejection sites of the martian meteorites are still unknown. Here, the authors build a database of 90 million craters and show that Tharsis region is the most likely source of depleted shergottites ejected 1.1 Ma ago, thus confirming that some portions of the mantle were recently anomalously hot.

The formation and differentiation of the crust of Mars in the first tens of millions of years after its accretion can only be deciphered from incredibly limited records. The martian breccia NWA 7034 and its paired stones is one of them. This meteorite contains the oldest martian igneous material ever dated: ~4.5 Ga old. However, its source and geological context have so far remained unknown. Here, we show that the meteorite was ejected 5–10 Ma ago from the north-east of the Terra Cimmeria—Sirenum province, in the southern hemisphere of Mars. More specifically, the breccia belongs to the ejecta deposits of the Khujirt crater formed 1.5 Ga ago, and it was ejected as a result of the formation of the Karratha crater 5–10 Ma ago. Our findings demonstrate that the Terra Cimmeria—Sirenum province is a relic of the differentiated primordial martian crust, formed shortly after the accretion of the planet, and that it constitutes a unique record of early crustal processes. This province is an ideal landing site for future missions aiming to unravel the first tens of millions of years of the history of Mars and, by extension, of all terrestrial planets, including the Earth. A new study pinpoints the ejection site of the 4.5-Ga-old Martian breccia NWA 7034 and paired stones to an area northeast of the Terra 679 Cimmeria–Sirenium province.

Impact craters are the most common feature on the Moon’s surface. Crater size–frequency distributions provide critical insight into the timing of geological events, surface erosion rates, and impact fluxes. The impact crater size–frequency follows a power law (meter‐sized craters are a few orders of magnitude more numerous than kilometric ones), making it tedious to manually measure all the craters within an area to the smallest sizes. We can bridge this gap by using a machine learning algorithm. We adapted a Crater Detection Algorithm to work on the highest resolution lunar image data set (Lunar Reconnaissance Orbiter‐Narrow‐Angle Camera [NAC] images). We describe the retraining and application of the detection model to preprocessed NAC images and discussed the accuracy of the resulting crater detections. We evaluated the model by assessing the results across six NAC images, each covering a different lunar area at differing lighting conditions. We present the model’s average true positive rate for small impact craters (down to 20 m in diameter) is 93%. The model does display a 15% overestimation in calculated crater diameters. The presented crater detection model shows acceptable performance on NAC images with incidence angles ranging between ∼50° and ∼70° and can be applied to many lunar sites independent to morphology. Plain Language Summary The Moon’s surface is covered in impact craters and recording their spatial density gives researchers the ability to study the geological evolution of our satellite. Analyzing craters helps in determining the physical properties of planetary surfaces and how/if impact rates change over time. These analyses rely on recording spatial densities for numerous surfaces, which has been achieved for craters >1–2 km on the Moon. Manually counting the smaller craters, which number in the hundreds of millions, is a daunting task. We adapted a Crater Detection Algorithm and applied it to the highest resolution lunar imagery data set. We describe our method for gathering, reformatting, and detecting craters across lunar images down to 20 m in diameter. The detection model performance was quantitatively evaluated across six different regions, each with different terrain and lighting conditions. Comparison between manually mapped craters and detections from our model allows us to conclude that the model has an acceptable performance in detecting fresh to moderately degraded craters of all sizes, down to 20 m in diameter, when compared to other studies. Automated crater detection complements manual counting methods and aids in unlocking secrets of the Moon’s surface. Key Points Adapted and retrained a Crater Detection Algorithm (using YOLOv3) to work on high‐resolution Lunar Reconnaissance Orbiter‐Narrow‐Angle Camera (NAC) images Developed a workflow for georeferencing and detecting craters down to 10 pixels in diameter across multiple overlapping NAC images Evaluation reveals acceptable performance in detecting craters on diverse terrains, across images with 50–70° incidence angles

Dating young lunar surfaces, such as impact ejecta blankets and terrains associated with recent volcanic activities, provides critical information on the recent events that shaped the surface of the Moon. Model age derivation of young or small areas using a crater chronology is typically achieved through manual counting, which requires a lot of small impact craters to be tediously mapped. In this study, we present the use of a Crater Detection Algorithm (CDA) to extract crater populations on Lunar Reconnaissance Orbiter—Narrow Angle Camera (LRO‐NAC) and Kaguya Terrain Camera images. We applied our algorithm to images covering the ejecta blankets of four Copernican impact craters and across four young mare terrains, where manually derived model ages were already published. Across the eight areas, 10 model ages were derived. We assessed the reproducibility of our model using two populations for each site: (a) an unprocessed population and (b) a population adjusted to remove contaminations of secondary and buried craters. The results showed that unprocessed detections led to overestimating crater densities by 12%–48%, but “adjusted” populations produced consistent results within <20% of published values in 80% of cases. Regarding the discrepancies observed, we found no significant error in our detections that could explain the differences with crater densities manually measured. With careful processing, we conclude that a CDA can be used to determine model ages and crater densities for the Moon. We also emphasize that automated crater datasets need to be processed, interpreted and used carefully, in unity with geologic reasoning. The presented approach can offer a consistent and reproducible way to derive model ages. Plain Language Summary Studying young lunar surfaces, such as impacted areas or volcanic activity, helps us understand recent events that have shaped the Moon's surface. Determining the model age of these areas generally involves manually counting small craters, which is time‐consuming and variable. This study presents a machine‐learning approach to detect craters on images acquired by the Lunar Reconnaissance Orbiter‐Narrow Angle Camera and the Kaguya Terrain Camera. Four impact craters and four young mare terrains were analyzed, where model ages had already been determined manually. When comparing our automatic counts to the manual counts, we observed that our results became more consistent with the published surface ages when we excluded secondary or buried craters from our crater populations. We also outline that automatic crater detection methods can be used to determine the age of lunar surfaces in a reliable and consistent manner when used correctly. Key Points Automatic crater counting of the Moon was achieved using a Convolutional Neural Network architecture and applied to LRO‐NAC and Kaguya Terrain Camera images Testing of the automatic counts against manual counts across the same count areas is required to provide confidence in the results Surface ages resulting from automatic crater counts are within acceptable error of model ages for the same area found using manual counts

Determining when an impact crater formed is a complex and tedious task. However, this knowledge is crucial to understanding the geological history of planetary bodies and, more specifically, gives information on erosion rate measurements, meteorite ejection location, impact flux evolution and the loss of a magnetic field. The derivation of an individual crater's age is currently performed through manual counting. Because crater size scales as a power law, this method is limited to small (and/or young) surface areas and, in the case of the derivation of crater emplacement age, to a small set of impact craters. Here, we used a Crater Detection Algorithm, specifically retrained to detect small impact craters on large‐ and high‐resolution imagery data set to solve this issue. We applied it to a global, 5 m/pixel resolution mosaic of Mars. Here, we test the use of this data set to date 10 large impact craters. We developed a cluster analysis tool in order to distinguish potential secondary crater clusters from the primary crater population. We then use this, filtered, crater population to date each large impact crater and evaluate our results against literature ages. We found that automated counting filtered through clustering analysis produced similar model ages to manual counts. This technique can now be expanded to much wider crater dating surveys, and by extension to any other kind of Martian surface. We anticipate that this new tool will considerably expand our knowledge of the geological events that have shaped the surface of Mars, their timing and duration. Plain Language Summary The age of an impact crater on a planetary surface is a crucial constraint in determining erosion rate, the crater source of Martian meteorites and the impact cratering flux evolution. This kind of measurement requires the counting of many impact craters superposed on the ejecta blanket of the considered crater and is therefore limited by human capability. To solve this issue, we adapted an automatic tool to detect small impact craters on the surface of Mars. We also developed an automatic approach to identify and remove clusters of small likely secondary craters detected by our algorithm. We assume these clusters of craters are formed by fragments ejected by an impact that formed a primary crater and need to be removed from crater densities used for age derivations. We applied our technique on 10 large Martian impact craters whose the formation age has been derived using manual counts and reported in the literature. We compared these ages to ours, derived from automatic count and automatic secondary craters filtering. Our results are consistent and indistinguishable from an age inferred from a manual count. For the first time, we demonstrate that an automated approach can deliver geologically meaningful model ages. Key Points Automatic detection of small craters on ejecta blanket of 10 large Martian craters Identification of secondary craters through cluster analysis Model ages from our semi‐automatic approach are similar from manual counts

The pharmacokinetics of 5-fluorouracil (5FU) were studied in vivo in patients with discrete tumors and in rabbits bearing VX2 tumors by using 19F NMR spectroscopy. The human studies were conducted in a 1.5-T Magnetom magnetic resonance imager (Siemens), and the rabbit studies were conducted in a 4.7-T GE/Nicolet 33-cm bore magnet. Free 5FU was detected in the tumors of four of the six patients and in all VX2 tumors but not in normal rabbit tissues. No other metabolites were seen in these tumors, contrary to the extensive catabolism we had previously documented using 19F NMR spectroscopy in both human and animal livers. The tumor pool of free 5FU in those human tumors that trapped 5FU was determined to have a half-life of 0.4-2.1 hr, much longer than expected and significantly longer than the half-life of 5FU in blood (5-15 min), whereas the half-life of trapped 5FU in the VX2 tumors ranged from 1.05 to 1.22 hr. In this initial experience, patient response to chemotherapy may correlate with extent of trapping free 5FU in the human tumors. These studies document that NMR spectroscopy is clinically feasible in vivo, allows noninvasive pharmacokinetic analyses at a drug-target tissue in real time, and may produce therapeutically important information at the time of drug administration. Demonstration of the trapping of 5FU in tumors provides both a model for studying metabolic modulation in experimental tumors (in animals) and a method for testing modulation strategies clinically (in patients).

In 1974, a statewide program was begun to improve surveillance of nosocomial infection in Virginia hospitals. Infection control practitioners were trained at the University of Virginia Hospital, Charlottesville, and were encouraged to submit monthly surveillance reports for analysis. In the first three years of the project, 141 students from 65 hospitals within the state attended a two-week basic course, with eight to 10 students per class. Of the 98 Virginia hospitals that sent students, 72 (73%) submitted monthly reports. The consistency of reporting (number of monthly reports received divided by the number of possible reporting months) was 83%. The sensitivity of reported data was estimated in comparative daily prospective surveys to be 69% for participating hospitals, and the specificity was 99%. The crude infection rate for the first 1.1 million patients at risk was 3.3%.

The pharmacokinetics of 5-fluorouracil (5FU) were studied in vivo in patients with discrete tumors and in rabbits bearing VX2 tumors by using super(19)F NMR spectroscopy. The human studies were conducted in a 1.5-T Magnetom magnetic resonance imager (Siemens), and the rabbit studies were conducted in a 4.7-T GE/Nicolet 33-cm bore magnet. Free 5FU was detected in the tumors of four of the six patients and in all VX2 tumors but not in normal rabbit tissues. No other metabolites were seen in these tumors, contrary to the extensive catabolism we had previously documented using super(19)F NMR spectroscopy in both human and animal livers. The tumor pool of free 5FU in those human tumors that trapped 5FU was determined to have a half-life of 0.4-2.1 hr, much longer than expected and significantly longer than the half-life of 5FU in blood (5-15 min), whereas the half-life of trapped 5FU in the VX2 tumors ranged from 1.05 to 1.22 hr.

Objective Over the past 30 years, clinician-educators have become a prominent component of medical school faculties, yet few of these individuals received formal training for this role and their professional development lags behind other faculty. This article reviews three residency tracks designed to build skills in teaching, curriculum development and assessment, education research, and career development to meet this need. Methods The residency clinician educator tracks at University of Michigan, Baylor College of Medicine, and University of California Davis are described in detail, with particular attention to their common elements, unique features, resource needs, and graduate outcomes. Results Common elements in the tracks are faculty mentorship, formal didactics, teaching opportunities, and an expectation of scholarly productivity. Essential resources include motivated faculty, departmental support, and a modest budget. Favorable outcomes include a high percentage of graduates in clinical faculty positions, teaching programs created by the residents, positive effects on recruitment, and enhancement of faculty identity as clinician educators. Conclusion Clinician-educator tracks in residency present a viable means to address the training needs of clinical track faculty. The programs described in this article provide a model to assist other departments in developing similar programs.

The impact flux over the last 3 Ga in the inner Solar System is commonly assumed to be constant through time. However, asteroid break-up events in the main belt may have been responsible for cratering spikes over the last ~2 Ga on the Earth-Moon system. We investigate here the possible variations of the size frequency distributions of impactors from the record of small craters of 521 martian impact craters larger than 20 km in diameter. We show that 49 craters (out of the 521) correspond to the complete crater population of this size formed over the last 600 Ma. Our results on Mars show that the flux of both small (> 5 m) and large asteroids (> 1 km) are coupled, does not vary between each other over the last 600 Ma. Existing data sets for large craters on the Earth and the Moon are analyzed and compared to our results on Mars. On Earth, we infer the formation location of a set of impact craters thanks to plate tectonic reconstruction and show that a cluster of craters formed during the Ordovician period, about 470 Ma ago, appears to be a preservation bias. On the Moon, the late increase seen in the crater age signal can be due to the uncertain calibration method used to date those impacts (i.e. rock abundance in lunar impact ejecta), and other calibrations are consistent with a constant crater production rate. We conclude to a coupling of the crater production rate between kilometer-size craters and down to ~100 m in diameter in the inner Solar System. This is consistent with the traditional model for delivering asteroids to planet-crossing orbits: the Yarkovsky effect slowly pushes the large debris from asteroid break-ups towards orbital resonances while smaller debris are grinded through collisional cascades. This suggests that the influence of past asteroid break-ups in the cratering rate for D > 100 m is limited or inexistent.