Minor Body Science with the Nancy Grace Roman Space Telescope

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Exploring the Bimodal Solar System via Sample Return from the Main Asteroid Belt: The Case for Revisiting Ceres

Abstract: Sample return from a main-belt asteroid has not yet been attempted, but appears technologically feasible. While the cost implications are significant, the scientific case for such a mission appears overwhelming. As suggested by the “Grand Tack” model, the structure of the main belt was likely forged during the earliest stages of Solar System evolution in response to migration of the giant planets. Returning samples from the main belt has the potential to test such planet migration models and the related geochemical and isotopic concept of a bimodal Solar System. Isotopic studies demonstrate distinct compositional differences between samples believed to be derived from the outer Solar System (CC or carbonaceous chondrite group) and those that are thought to be derived from the inner Solar System (NC or non-carbonaceous group). These two groups are separated on relevant isotopic variation diagrams by a clear compositional gap. The interface between these two regions appears to be broadly coincident with the present location of the asteroid belt, which contains material derived from both groups. The Hayabusa mission to near-Earth asteroid (NEA) (25143) Itokawa has shown what can be learned from a sample-return mission to an asteroid, even with a very small amount of sample. One scenario for main-belt sample return involves a spacecraft launching a projectile that strikes an object and flying through the debris cloud, which would potentially allow multiple bodies to be sampled if a number of projectiles are used on different asteroids. Another scenario is the more traditional method of landing on an asteroid to obtain the sample. A significant range of main-belt asteroids are available as targets for a sample-return mission and such a mission would represent a first step in mineralogically and isotopically mapping the asteroid belt. We argue that a sample-return mission to the asteroid belt does not necessarily have to return material from both the NC and CC groups to viably test the bimodal Solar System paradigm, as material from the NC group is already abundantly available for study. Instead, there is overwhelming evidence that we have a very incomplete suite of CC-related samples. Based on our analysis, we advocate a dedicated sample-return mission to the dwarf planet (1) Ceres as the best means of further exploring inherent Solar System variation. Ceres is an ice-rich world that may be a displaced trans-Neptunian object. We almost certainly do not have any meteorites that closely resemble material that would be brought back from Ceres. The rich heritage of data acquired by the Dawn mission makes a sample-return mission from Ceres logistically feasible at a realistic cost. No other potential main-belt target is capable of providing as much insight into the early Solar System as Ceres. Such a mission should be given the highest priority by the international scientific community

Detailed Mineralogical Characterizations of Four S-Asteroids: 138 Tolosa, 306 Unitas, 346 Hermentaria, and 480 Hansa

The S-asteroid taxonomic class is the second largest grouping of main-belt asteroids that are primarily located in the inner main belt (a < 3.0 AU) [1]. These asteroids have historically been the subject of interest within the asteroid community for several reasons. Continuing discussions about the nature of the S-asteroids (ordinary chondrite-like or thermally-evolved) and the putative space weathering effect on S-asteroids serve as examples of issues currently unresolved within the community [2,3]. Despite this general interest, detailed mineralogical investigations of individual S-asteroids has been relatively rare. A few workers have studied individual, or small groups of, S-asteroids [4,5,6,7]. Gaffey et al. [2] published their S-asteroid survey in 1993 that characterized 39 of the 144 then-classified S-asteroids. Despite the work already accomplished, the need exists to rigorously characterize the remaining S-asteroid population to gain a better understanding of these asteroids origin, nature, and physical characteristics

Composition and stratification of a tachinid (Diptera: Tachinidae) parasitoid community in a European temperate plain forest

1. We analysed the canopy and understorey communities of flies in the family Tachinidae, the most diverse group of parasitoid Diptera, in a small and isolated temperate plain forest in northern Italy. Our objective was to assess whether and how these communities differ from one another, and how species distribution relates to forest structure, host distribution, mating sites, and season. 2. The study was carried out in 2008 with 14 Malaise traps installed between April and November in an equal number of sites randomly selected inside the forest, seven on the ground and seven in the tree canopy. 3. Overall species richness, abundance, and turnover were greater in the understorey traps, but most diversity metrics indicate greater overall diversity and evenness in the canopy traps. Community ordination and estimates of beta diversity indicate that the two habitat-associated communities are distinct and should both be considered in assessments of insect diversity and community structure. Indicator species values revealed the presence of a number of species that were effective indicators of canopy and understorey habitats. No strong male bias in canopy traps was observed across species; however, the only significant sex ratio biases in the canopy were towards males. Both male and female biases were observed in understorey traps, depending upon the species

Composition and stratification of a tachinid (Diptera: Tachinidae) parasitoid community in a European temperate plain forest

1. We analysed the canopy and understorey communities of flies in the family Tachinidae, the most diverse group of parasitoid Diptera, in a small and isolated temperate plain forest in northern Italy. Our objective was to assess whether and how these communities differ from one another, and how species distribution relates to forest structure, host distribution, mating sites, and season. 2. The study was carried out in 2008 with 14 Malaise traps installed between April and November in an equal number of sites randomly selected inside the forest, seven on the ground and seven in the tree canopy. 3. Overall species richness, abundance, and turnover were greater in the understorey traps, but most diversity metrics indicate greater overall diversity and evenness in the canopy traps. Community ordination and estimates of beta diversity indicate that the two habitat-associated communities are distinct and should both be considered in assessments of insect diversity and community structure. Indicator species values revealed the presence of a number of species that were effective indicators of canopy and understorey habitats. No strong male bias in canopy traps was observed across species; however, the only significant sex ratio biases in the canopy were towards males. Both male and female biases were observed in understorey traps, depending upon the species

Asymmetric hybridization in Cordulegaster (Odonata: Cordulegastridae): Secondary postglacial contact and the possible role of mechanical constraints

Two Cordulegaster dragonflies present in Italy, the Palaearctic and northern distributed Cordulegaster boltonii and the endemic to the south of the peninsula Cordulegaster trinacriae, meet in central Italy and give rise to individuals of intermediate morphology. By means of mitochondrial and nuclear markers and of Geometric Morphometrics applied to sexual appendages, we defined i) the geographical boundaries between the two species in Italy and ii) we determined the presence, the extent, and the genetic characteristics of the hybridization. Genetic data evidenced asymmetric hybridization with the males of C.trinacriae able to mate both interspecifically and intraspecifically. The results contrast with expectations under neutral gene introgression and sexual selection. This data, along with the morphological evidence of significant differences in size and shape of sexual appendages between the males of the two species, seem indicative of the role of mechanical constraints in intraspecific matings. The origin of the two species is dated about to 1.32 Mya and the hybridization resulted related to range expansion of the two species after Last Glacial Maximum and this led to the secondary contact between the two taxa in central Italy. At last, our results indicate that the range of C.trinacriae, a threatened and protected species, has been moving northward probably driven by climate changes. As a result, the latter species is currently intruding into the range of C.boltonii. The hybrid area is quite extended and the hybrids seem well adapted to the environment. From a conservation point of view, even if C.trinacriae has a strong genetic identity, the discovery of hybridization between the two species should be considered in a future species management