The Pioneer and Voyager spacecraft made close-up measurements of Saturn's ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and ...atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn's atmosphere from infalling material. The Cassini Ion Neutral Mass Spectrometer sampled in situ the region between the D ring and Saturn during the spacecraft's Grand Finale phase. We used these measurements to characterize the atmospheric structure and material influx from the rings. The atmospheric He/H
ratio is 10 to 16%. Volatile compounds from the rings (methane; carbon monoxide and/or molecular nitrogen), as well as larger organic-bearing grains, are flowing inward at a rate of 4800 to 45,000 kilograms per second.
The MAss Spectrometer for Planetary EXploration (MASPEX) is a high-mass-resolution, high-sensitivity, multi-bounce time-of-flight mass spectrometer (MBTOF) capable of measuring minor species with ...abundances of sub-parts-per-million in Europa’s sputter-produced and radiolytically modified exosphere and in its oceanic plumes. The goal of the MASPEX-Europa investigation is to determine, through in-situ measurement of the exosphere and plume composition, whether the conditions for habitability exist or have existed on Europa. As conventionally defined, based on our knowledge of Earth life, the three fundamental conditions for habitability are: (1) the presence of liquid water; (2) the presence of organic compounds and the biogenic elements CHNOPS; and (3) a source of energy available for metabolic processes, which for Europa will most probably be chemosynthetic rather than photosynthetic. Condition (1) is already established by previous indirect (magnetic field) measurements, while MASPEX will contribute directly to the evaluation of condition (2) through highly specific compositional measurements in the Europan exosphere and plumes. The composition measurements will also contribute to the test of condition (3) through disequilibrium states of chemical reactions. Thus, the primary goal of MASPEX for Europa Clipper is to assess the habitability of Europa and specifically of its interior ocean. MASPEX has been developed successfully, and its calibration has demonstrated that it meets its specified requirements for sensitivity, dynamic range, and mass resolution. This paper reports the development of the MASPEX scientific investigation, the instrument, its performance, and calibration.
During Cassini's final, spectacular months, in situ instruments made the first direct measurements of nanoparticles, finding an exceptionally large flow from the rings into Saturn's atmosphere. ...Cassini's Ion and Neutral Mass Spectrometer measured material in three altitude bands and found a global‐integrated flux of 2–20 × 104 kg/s that is dominated by hydrocarbon material <104u. Ranging from clusters of a few molecules to radii of several nanometers, nanoparticles are ubiquitous throughout Saturn's rings but embedded in the regolith of larger particles and not detectable as independent particles using remote observations. The smallest nanoparticles are susceptible to atmosphere drag by Saturn's tenuous exosphere that reaches the inner edge of the D ring. The unsustainable large flux suggests a recent disturbance of Saturn's inner ring material, possibly associated with the clumping that appeared in the D68 ringlet in 2015.
Plain Language Summary
For 40 years, calculations based on remote observations indicated that Saturn's magnetic field carries ions and charged particles from the rings to the midlatitudes of Saturn. In Cassini's last few months of life, direct, in situ measurements found that 10 tons/s of molecules and particles smaller than two nanometers are streaming along the plane of the rings into Saturn's atmosphere by another process: atmospheric drag. Saturn's extended atmosphere reaches the inner edge of Saturn's rings and extracts neutral particles less than one thousandth the thickness of a human hair by slowing them down until they fall into Saturn. Surprisingly, the flux is a hundred times larger than past predictions, and at least half of the material is hydrocarbon, which comprises less than 5% of the water ice‐dominated rings. Cassini's data also show that the influx varies at least a factor of 4 and may be linked to clumps that appeared in 2015 on D68, the ringlet on the inner edge of the rings. These newly discovered particles and processes alter the evolutionary landscape of the rings and provide an exciting, rich field for future research aimed at understanding the origin and history of the rings.
Key Points
Atmospheric drag, an interaction newly applied to Saturn and its rings, extracts >104 kg/s of neutral nanoparticles from Saturn's rings
Molecules and particles <2 nm in radius are preferentially transported by atmospheric drag
Neutral, nanometer‐sized hydrocarbon material is currently the largest mass loss from Saturn's rings
Two experiments were conducted to examine the effects of different corn titration diets and dietary adaptation period length (DAPL) on intestinal histology, apparent ileal P digestibility (AIPD), and ...apparent P retention (APR) in Ross × Ross 708 male broilers from 20 to 24 d of age. It was hypothesized that purified ingredients in nutrient-deficient titration diets may affect P availability with varying DAPL. In experiment 1, 1,152 broilers were utilized in a 3 × 3 factorial treatment structure with 3 diets (control, 25% corn titration diet 25CTD, or 75% corn titration diet 75CTD) and 3 DAPL (0, 24, or 72 h). Experiment 2 was conducted with 576 broilers as a 4 × 3 factorial arrangement with 4 diets (control, 25CTD, 75CTD, or nitrogen-free diet NFD) and 3 DAPL (24, 48, or 72 h). All diets contained purified ingredients except for the control diet, which had the same formulation as the common starter and served as a control for DAPL. The NFD diet was fed as a highly purified protein-free diet. Broilers were fed a common diet until 19 d of age and then transferred to experimental diets at 20 d of age. In experiment 1, diet type did not affect (P > 0.05) intestinal histology. However, diet type and DAPL each influenced (P.≤.0.001) diet AIPD. Higher (P.≤.0.001) AIPD was measured for the control diet compared with the 75CDT, and the 25CTD had the lowest AIPD. Following a 24 h DAPL, AIPD was higher (P.≤.0.001) than after a DAPL of 0 or 72 h. In experiment 2, diet type × DAPL interactions (P.≤.0.001) were observed for APR of the control diet, 75CTD, and NFD, but not the 25CTD. Because APR of the control diet was affected by varying DAPL, factors other than differences in diet type may have been responsible for inconsistencies in the measure of P availability. Furthermore, no clear evidence was observed that broilers were able to adapt to P-deficient diets by increasing APR or AIPD. In conclusion, a standard DAPL should be established as a means to reduce variability associated with measuring of feedstuff P availability.
During Cassini's Grand Finale, the spacecraft flew between Saturn's upper atmosphere and its innermost ring, the D ring. Throughout these final orbits, Cassini encountered material flowing from the D ...ring into Saturn's atmosphere. Here, we present a compositional analysis of this material using data collected by Cassini's Ion Neutral Mass Spectrometer. We confirm the identification of CH4, CO2, CO, N2, H2O, NH3, and organics in the ring material, and provide upper limits for organic compounds of interest. The H/C, O/C, N/C, and S/C ratios of ring material are constrained using three different kinds of model spectra: automated fits, hand fits of inorganics + hydrocarbons, and hand fits of inorganics + organics with priority given to O-, N-, and S-bearing organics. Additionally, we compare data from the final plunge to earlier orbits, and find that ring material can be divided into gas and dust constituents, with CO2 at the volatility boundary between the two phases. At increasing distance above the equatorial plane, the gas/dust molar ratio increases.
•INMS measured complex material from the D ring during the Cassini Grand Finale.•This material is ~20% water and ~35% non-methane organics by mass.•Constraints on elemental ratios of the ring material are presented.•Ring material is latitudinally fractionated according to gas and dust components.
Little is known about the attributional patterns of caregivers of autistic children, particularly in relation to caregivers of children with other developmental or behavioral disorders. This study ...examined differences in caregiver attributions of child behavior between three groups: toddlers with (1) Autism spectrum disorder (ASD) or ASD concerns; (2) Other developmental concerns; and (3) No concerns. Qualitative descriptions of actual child behaviors were coded using a three-stage content analysis. Regression analyses were utilized to determine if group membership predicted types of positive and challenging behaviors caregivers endorsed, as well as their attributions of these behaviors. Caregivers of children with ASD or ASD concerns endorsed similar types of behaviors, but rated their child’s positive behaviors as less characteristic of their child and more a function of the particular situation, less stable or permanent, and less controllable as compared to caregivers of toddlers with other developmental or no concerns. Additionally, they rated their child’s challenging behaviors as more stable or permanent and less controllable as compared to caregivers of toddlers with other developmental concerns or no concerns. These findings suggest that caregivers of children with ASD and ASD related concerns may be vulnerable to a negative attributional pattern, which can have important implications for child and family functioning and overall quality of life.
Many shark and ray species show affinity to specific sites, making these areas critical for their survival. These include cleaning stations: locations on reefs where cleaner fish remove parasites and ...clean wounds, which is important for maintaining health. Cleaning stations also function as social gathering sites, or resting points, where courtship and mating can occur. In this study, we identify an aggregation site for the shortfin devil ray,
Mobula kuhlii
(Family Mobulidae) within the Aliwal Shoal Marine Protected Area in KwaZulu-Natal (KZN), South Africa, and document their behavior. Remote underwater video was used to collect footage of
M. kuhlii
being cleaned by blue streak cleaner wrasse,
Labroides dimidiatus
. Generalized additive models (GAMs) were used to assess environmental predictors of
M. kuhlii
presence on Aliwal Shoal. Mixed models were used to assess the same environmental predictors and their correlation with mean
M. kuhlii
cleaning duration and number of
L. dimidiatus
bites per second at the identified cleaning station site.
M. kuhlii
were present in 56% of observation days, with group numbers up to > 150 individuals. Sea surface temperature was a significant predictor for
M. kuhlii
presence, while a north to south current was significantly associated with longer mean cleaning durations. These results support findings of mobulid studies in KZN that show increased habitat use during summer temperatures (24–25 °C) and suggest these sites to be important for individual health and social interaction. We hope these findings can be used for development of location-specific management plans to safeguard this Endangered species.
Conservation of undrained tropical peatland ecosystems is critical for climate change mitigation as they store a tremendous amount of soil carbon that is preserved under anoxic water-logged ...conditions. Unfortunately, there are too few measurements of carbon fluxes from these ecosystems to estimate the climate change mitigation potential from such conservation efforts. Here, we measured carbon dioxide (CO
) and methane (CH
) fluxes as well as fluvial organic carbon export over the peat swamp forest within an undrained tropical peatland landscape in East Kalimantan, Indonesia. Our measurements throughout one year (Oct 2022-Sep 2023) showed that despite its water-logged condition, peat and water overlying the swamp forest on average emits 11.02 ± 0.49 MgCO
ha
yr
of CO
and 0.58 ± 0.04 MgCO
e ha
yr
of CH
. Further, the fluvial organic carbon export contributes to additional carbon loss of 1.68 ± 0.06 MgCO
e ha
yr
. Our results help improve the accuracy of carbon accounting from undrained tropical peatlands, where we estimated a total carbon loss of 13.28 ± 0.50 MgCO
e ha
yr
. Nevertheless, the total carbon loss reported from our sites is about half than what is reported from the drained peatland landscapes in the region and resulted in a larger onsite carbon sink potential estimate compared to other undrained peat swamp forests. Together, these findings indicate that conserving the remaining undrained peatland ecosystems in Indonesia from drainage and degradation is a promising natural climate solution strategy that avoids significant carbon emissions.
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