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

Clear cell carcinoma of the ovary arising in a mucinous cystadenoma

A 57 year old woman presented complaining of increasing abdominal swelling of six months duration. A mixed solid cystic left ovarian tumour measuring 24 cm in diameter was excised. Histology showed numerous cysts lined by benign mucinous epithelium blending imperceptibly into borderline clear cell and mucinous areas that in turn merged with an invasive clear cell carcinoma. To the best of our knowledge, this is the first reported case of clear cell carcinoma arising in a mucinous cystadenoma. The implications for the previously postulated pathogenesis of these tumours are discussed. Key Words: ovary • clear cell carcinoma • mucinous cystadenom

Comparison of Near Infrared Reflectance Spectroscopy and Raman Spectroscopy for Predicting Botanical Composition of Cattle Diets

Diet selection is an important driver of ecosystem structure and function that is difficult to measure. New spectroscopic instruments are available for evaluating their applicability to ecological field studies. The objective of this study was to compare near-infrared reflectance spectroscopy (NIRS) to Raman spectroscopy of fecal samples for predicting the percentage of honey mesquite (Prosopis glandulosa) in the diet of ruminally fistulated cattle fed three different hay diets and compare them for their ability to discriminate among the three base diets. Spectra were collected from feces from a feeding trial with mesquite fed at 0%, 1%, 3%, and 5% of the diet and base hay diets of timothy hay (Phleum pratense), Sudan hay (Sorghum sudanense), or a 50:50 combination of Bermudagrass hay (Cynodon dactylon) and beardless wheat hay (Triticum aestivum). NIRS and Raman spectra were used for partial least squares regression calibrations with the timothy and Sudan hays and validated with the Bermudagrass/ beardless wheat hay diets. NIRS spectra provided useful calibrations (r2 = 0.88, slope = 1.03, intercept = 1.88, root mean square error = 2.09, bias = 1.95, ratio of performance to deviation = 2.6), but Raman spectra did not. Stepwise discriminant analysis was used to select wavenumbers for discriminating among the hays. Fifteen of 350 possible wavenumbers for NIRS spectra and 29 of 300 possible wavenumbers for Raman spectra met the P ≤ 0.05 entry and staying criteria. Canonical discriminant analysis using these wavenumbers resulted in 100% correct classification for all three base diets, and the Raman spectra provided greater separation than NIRS spectra. Discrimination using Raman spectra was primarily associated with wavenumbers associated with undigestible constituents of the diet (lignin). In contrast, discrimination using fecal NIRS (f.NIRS) spectra was primarily associated with wavenumbers associated with digestible constituents in the diet (protein, starch, and lipid). We believe that Raman spectroscopy deserves further investigation as a quantitative technique in ecological field studies. © 2017 The Society for Range Management. Published by Elsevier Inc. All rights reserved.The Rangeland Ecology & Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information

Revised concept for the Waste Isolation Pilot Plant

The quantities of remotely handled wastes that must be handled at the Waste Isolation Pilot Plant have been reduced from 250 x 10/sup 3/ ft/sup 3//y to 10 x 10/sup 3/ ft/sup 3//y; the capital cost of the facility will be reduced from 534 to 428 million dollars. Changes in the facility design due to the reduction in the amount of remote-handled waste are discussed. If DOE should exercise its option to construct a high-level waste repository concurrently with the construction of the revised design, with both facilities receiving waste in 1985, the combined cost would be about 580 million dollars. However, it is unlikely that significant quantities of high-level waste in a form suitable for geologic disposal would be available until after 1990. (13 figures, 5 tables) (DLC