Imaging Lunar Craters with the Lucy Long Range Reconnaissance Imager (L'LORRI): A Resolution Test for NASA's Lucy Mission

NASA's Lucy mission is designed to better understand the unique population of Trojan asteroids. Trojans were probably captured in Jupiter's L4 and L5 points early in the solar system's evolution and little altered since then. A critical investigation of Lucy is to use its highest-resolution camera, the Lucy Long Range Reconnaissance Imager (L'LORRI), to image Trojans' surfaces to understand their geology and impact crater populations. Through crater statistics, the population of smaller bodies that produced those impacts, relative age differences across the bodies, and other comparative investigations between bodies can be studied. Mapping the crater population to the minimum diameters needed to achieve Lucy's objectives might require image subsampling and deconvolution ("processing") to improve the spatial resolution, a process whereby multiple, slightly offset images are merged to create a single, better-sampled image and deconvolved with L'LORRI's point-spread function. Lucy's first Earth Gravity Assist (EGA1) provided an opportunity to test this process's accuracy using L'LORRI images of the Moon, whose crater population is well characterized and therefore provides ground-truth testing. Specifically, the lunar crater imaging by L'LORRI during EGA1 allowed us to compare crater statistics derived from raw and processed L'LORRI images with ground-truth statistics derived from higher-resolution lunar imaging from other missions. The results indicate the processing can improve impact crater statistics such that features can be identified and measured to ~70% the diameter that they can otherwise be reliably mapped on native L'LORRI images. This test's results will be used in the observation designs for the Lucy flyby targets

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio

The Retinoic Acid Receptor Agonist Am80 Increases Mucosal Inflammation in an IL-6 Dependent Manner During Trichuris muris Infection

PURPOSE: Vitamin A metabolites, such as all-trans-retinoic acid (RA) that act through the nuclear receptor; retinoic acid receptor (RAR), have been shown to polarise T cells towards Th2, and to be important in resistance to helminth infections. Co-incidentally, people harbouring intestinal parasites are often supplemented with vitamin A, as both vitamin A deficiency and parasite infections often occur in the same regions of the globe. However, the impact of vitamin A supplementation on gut inflammation caused by intestinal parasites is not yet completely understood. METHODS: Here, we use Trichuris muris, a helminth parasite that buries into the large intestine of mice causing mucosal inflammation, as a model of both human Trichuriasis and IBD, treat with an RARα/β agonist (Am80) and quantify the ensuing pathological changes in the gut. RESULTS: Critically, we show, for the first time, that rather than playing an anti-inflammatory role, Am80 actually exacerbates helminth-driven inflammation, demonstrated by an increased colonic crypt length and a significant CD4(+) T cell infiltrate. Further, we established that the Am80-driven crypt hyperplasia and CD4(+) T cell infiltrate were dependent on IL-6, as both were absent in Am80-treated IL-6 knock-out mice. CONCLUSIONS: This study presents novel data showing a pro-inflammatory role of RAR ligands in T. muris infection, and implies an undesirable effect for the administration of vitamin A during chronic helminth infection. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10875-013-9936-8) contains supplementary material, which is available to authorized users

Investigating the DART Impact Event with the Lucy LOng Range Reconnaissance Imager

NASA’s Lucy mission is the first to provide flyby reconnaissance of the Jovian trojan asteroids, which are thought to be primordial small bodies that formed at a variety of heliocentric distances during the early stages of the solar system’s formation and were subsequently captured into Jupiter’s L4 and L5 Lagrange stability zones. Since its successful launch on 2021-Oct-16, the Lucy spacecraft has been orbiting the sun within the inner solar system. On 2022-Oct-16, Lucy executes the first of three Earth Gravity Assists (EGAs) that put the spacecraft on the correct trajectory to achieve its encounters with the Jovian trojans. The DART kinetic impact on the secondary body of the Didymos-Dimorphos binarysystem occurs 20 days prior to EGA1, at a time when the Lucy spacecraft is well-placed to observe it. Lucy carries a sensitive panchromatic camera, the Lucy LOng Range Reconnaissance Imager (L’LORRI), which is capable of detecting the binary system with high signal-to-noise ratio (SNR) and with temporal cadences as fast as once per second. The observing geometry from Lucy is similar to that from the Earth: the range to the Didymos system is 0.126 au from Lucy vs 0.0757 au from Earth, and the solar phase angle is 31.9 deg vs 53.2 deg. The L’LORRI investigation of the DART impact event is divided into eight separate observational phases, starting 12 hr before the impact and ending 24 hr afterwards. L’LORRI cannot resolve the binary, but instead records the total brightness, which is expected to increase after the DART impact due to reflected sunlight from the ejecta. The first two phases are designed to obtain baseline photometry of the Didymos system covering both the Didymos-Dimorphos mutual orbit period (11.92 hr) and the rotational period of Didymos (2.26 hr). Phase 3 covers the impact event itself at one second cadence, starting 3 minutes beforeimpact and ending 4 minutes afterwards. Lucy has a clear view of the predicted DART impact site, theoretically enablingL’LORRI to detect an optical flash in the unlikely event it is brighter than Didymos itself. L’LORRI observations during phases 4 through 8 are designed to monitor the temporal and spatial evolution of ejecta associated with the impact event, but ejecta don’t leave the central pixel during Lucy’s observing period unless their speed is greater than about 2 m/s

Zfp488 promotes oligodendrocyte differentiation of neural progenitor cells in adult mice after demyelination

Basic helix-loop-helix transcription factors Olig1 and Olig2 critically regulate oligodendrocyte development. Initially identified as a downstream effector of Olig1, an oligodendrocyte-specific zinc finger transcription repressor, Zfp488, cooperates with Olig2 function. Although Zfp488 is required for oligodendrocyte precursor formation and differentiation during embryonic development, its role in oligodendrogenesis of adult neural progenitor cells is not known. In this study, we tested whether Zfp488 could promote an oligodendrogenic fate in adult subventricular zone (SVZ) neural stem/progenitor cells (NSPCs). Using a cuprizone-induced demyelination model in mice, we examined the effect of retrovirus-mediated Zfp488 overexpression in SVZ NSPCs. Our results showed that Zfp488 efficiently promoted the differentiation of the SVZ NSPCs into mature oligodendrocytes in vivo. After cuprizone-induced demyelination injury, Zfp488-transduced mice also showed significant restoration of motor function to levels comparable to control mice. Together, these findings identify a previously unreported role for Zfp488 in adult oligodendrogenesis and functional remyelination after injury

HLA-DQA1*05 carriage associated with development of anti-drug antibodies to infliximab and adalimumab in patients with Crohn's Disease

Anti-tumor necrosis factor (anti-TNF) therapies are the most widely used biologic drugs for treating immune-mediated diseases, but repeated administration can induce the formation of anti-drug antibodies. The ability to identify patients at increased risk for development of anti-drug antibodies would facilitate selection of therapy and use of preventative strategies.This article is freely available via Open Access. Click on Publisher URL to access the full-text

Lucy Mission to the Trojan Asteroids: Science Goals

The Lucy Mission is a NASA Discovery-class mission to send a highly capable and robust spacecraft to investigate seven primitive bodies near both the L4 and L5 Lagrange points with Jupiter: the Jupiter Trojan asteroids. These planetesimals from the outer planetary system have been preserved since early in solar system history. The Lucy mission will fly by and extensively study a diverse selection of Trojan asteroids, including all the recognized taxonomic classes, a collisional family member, and a near equal-mass binary. It will visit objects with diameters ranging from roughly 1 km to 100 km. The payload suite consists of a color camera and infrared imaging spectrometer, a high-resolution panchromatic imager, and a thermal infrared spectrometer. Additionally, two spacecraft subsystems will also contribute to the science investigations: the terminal tracking cameras will supplement imaging during closest approach and the telecommunication subsystem will be used to measure the mass of the Trojans. The science goals are derived from the 2013 Planetary Decadal Survey and include determining the surface composition, assessing the geology, determining the bulk properties, and searching for satellites and rings

Health outcomes among HIV-positive Latinos initiating antiretroviral therapy in North America versus Central and South America

Introduction: Latinos living with HIV in the Americas share a common ethnic and cultural heritage. In North America, Latinos have a relatively high rate of new HIV infections but lower rates of engagement at all stages of the care continuum, whereas in Latin America antiretroviral therapy (ART) services continue to expand to meet treatment needs. In this analysis, we compare HIV treatment outcomes between Latinos receiving ART in North America versus Latin America. Methods: HIV-positive adults initiating ART at Caribbean, Central and South America Network for HIV (CCASAnet) sites were compared to Latino patients (based on country of origin or ethnic identity) starting treatment at North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD) sites in the United States and Canada between 2000 and 2011. Cox proportional hazards models compared mortality, treatment interruption, antiretroviral regimen change, virologic failure and loss to follow-up between cohorts. Results: The study included 8400 CCASAnet and 2786 NA-ACCORD patients initiating ART. CCASAnet patients were younger (median 35 vs. 37 years), more likely to be female (27% vs. 20%) and had lower nadir CD4 count (median 148 vs. 195 cells/µL, p<0.001 for all). In multivariable analyses, CCASAnet patients had a higher risk of mortality after ART initiation (adjusted hazard ratio (AHR) 1.61; 95% confidence interval (CI): 1.32 to 1.96), particularly during the first year, but a lower hazard of treatment interruption (AHR: 0.46; 95% CI: 0.42 to 0.50), change to second-line ART (AHR: 0.56; 95% CI: 0.51 to 0.62) and virologic failure (AHR: 0.52; 95% CI: 0.48 to 0.57). Conclusions: HIV-positive Latinos initiating ART in Latin America have greater continuity of treatment but are at higher risk of death than Latinos in North America. Factors underlying these differences, such as HIV testing, linkage and access to care, warrant further investigation