Cassini detection of Enceladus' cold water-group plume ionosphere

This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O+, OH+, H2O+, H3O+) and heavier water dimer ions (HxO(2))(+) very close to Enceladus where the plasma begins to emerge from the plume. The data were obtained during two close ( 52 and 25 km) flybys of Enceladus in 2008 and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction exhibiting energies consistent with the Cassini speed, indicative of a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enceladus signatures of the plasma interaction with the plume are detected 22 Enceladus radii away. Citation: Tokar, R. L., R. E. Johnson, M. F. Thomsen, R. J. Wilson, D. T. Young, F. J. Crary, A. J. Coates, G. H. Jones, and C. S. Paty ( 2009), Cassini detection of Enceladus' cold water-group plume ionosphere, Geophys. Res. Lett., 36, L13203, doi:10.1029/2009GL038923

Cometary science after Rosetta

The European Space Agency’s Rosetta mission ended operations on 30 September 2016 having spent over 2 years in close proximity to its target comet, 67P/Churyumov–Gerasimenko. Shortly before this, in summer 2016, a discussion meeting was held to examine how the results of the mission could be framed in terms of cometary and solar system science in general. This paper provides a brief history of the Rosetta mission, and gives an overview of the meeting and the contents of this associated special issue

Discovery of a transient radiation belt at Saturn

Radiation belts have been detected in situ at five planets. Only at Earth however has any variability in their intensity been heretofore observed, in indirect response to solar eruptions and high altitude nuclear explosions. The Cassini spacecraft's MIMI/LEMMS instrument has now detected systematic radiation belt variability elsewhere. We report three sudden increases in energetic ion intensity around Saturn, in the vicinity of the moons Dione and Tethys, each lasting for several weeks, in response to interplanetary events caused by solar eruptions. However, the intensifications, which could create temporary satellite atmospheres at the aforementioned moons, were sharply restricted outside the orbit of Tethys. Unlike Earth, Saturn has almost unchanging inner ion radiation belts: due to Saturn's near-symmetrical magnetic field, Tethys and Dione inhibit inward radial transport of energetic ions, shielding the planet's main, inner radiation belt from solar wind influences

Factors associated with parents’ and adolescents’ perceptions of oral health and need for dental treatment

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72207/1/j.1600-0528.2006.00336.x.pd

Telecentric F-theta fisheye lens for space applications

A very wide angle lens with a field of view of 360°x180° - a fisheye lens - has been designed to be used in a space environment. As a case study, the lens is assumed to be mounted on a spinning probe passing through a comet’s tail. The lens, rotating with the probe passing through the comet coma, may map the entire sky as viewed from the interior tail, providing unprecedented data on the spatial distribution of plasma and dust. Considering the foreseen space applications for the lens, radiation hardened glass has been taken into account for the design. A key feature of the lens is the “angular scale” uniformity (F-theta) of the sky distribution map projected on the focal plane allowing to obtain a reliable whole sky reconstruction. Care has also been taken to obtain an almost telecentric design, in order to permit filters placed on the focal plane to work properly. A telecentric fisheye operating with a pixel-limited resolution in the waveband from 500 nm up to 770 nm and with an F-theta distortion is presented in this paper

The role of hip abductor strength on the frontal plane of gait in subjects with medial knee osteoarthritis

Objective: This study aimed to investigate the relationship of hip abductor strength with external hip and knee adduction moments, pain and physical function, and trunk, pelvis, and hip kinematics in the frontal plane during walking in subjects with medial knee osteoarthritis. Methods: Twenty-five subjects with medial knee osteoarthritis were evaluated through an isokinetic strength test for hip abductor, three-dimensional gait analysis (kinetics and kinematics), pain and physical function scores. Regression models were used to control the influence of other parameters such as pain, age, gender, severity, walking speed, mass and height. Results: No relationship was found of hip abductor strength with peak of external knee adduction moment and knee adduction angular impulse. Hip abductor strength explained 17% of contralateral pelvic drop and 21% of hip adduction angle. In addition, hip abductor strength explained 4% and 1% of the variance in the WOMAC physical function score and 40 meter fast paced walk test, respectively. Conclusion: Considering the relationship of hip abductor strength with contralateral pelvic drop and hip adduction angle, specific exercises might improve physical function and lower limb dynamic alignment during gait

Evidence of potential establishment of pink salmon Oncorhynchus gorbuscha in Scotland.

In spring 2022, pink salmon Oncorhynchus gorbuscha smolts were recorded in the UK. Fish were caught in the Rivers Thurso and Oykel in Scotland between 13 and 17 March. To the authors' knowledge, this is the first observation of O. gorbuscha smolts in Europe outside the Scandinavian and Kola peninsulas, including other tributaries of the White and Barents Seas. It also provides evidence of successful spawning in 2021 and completion of the freshwater phase of the life cycle, and indicates the possibility for potential establishment of an O. gorbuscha population in Great Britain

Detection of negative pickup ions at Saturn's moon Dione

We investigate a possible negative ion feature observed by the Cassini Plasma Spectrometer (CAPS) during a flyby of Saturn's moon Dione that occurred on April 7, 2010. By examining possible particle trajectories, we find that the observed particles are consistent with negative pick‐up ions originating near the moon's surface. We find that the mass of the negative pick‐up ions is in the range of 15 – 25 u and tentatively identify this species as O‐, likely resulting from ionization and subsequent pick‐up from Dione's O2‐CO2 exosphere. Our estimates show that the negative ion density is ~3 x 10‐3 cm‐3. This is comparable to, but slightly smaller than, that previously reported for the density of O2+ pick‐up ions for the same flyby, indicating that negative pick‐up ions may represent a major loss channel for Dione's exosphere

Survey of pickup ion signatures in the vicinity of Titan using CAPS/IMS

Pickup ion detection at Titan is challenging because ion cyclotron waves are rarely detected in the vicinity of the moon. In this work, signatures left by freshly produced pickup heavy ions (m/q ∼ 16 to m/q ∼ 28) as detected in the plasma data by the Cassini Plasma Spectrometer/Ion Mass Spectrometer (CAPS/IMS) instrument on board Cassini are analyzed. In order to discern whether these correspond to ions of exospheric origin, one of the flybys during which the reported signatures were observed is investigated in detail. For this purpose, ion composition data from time-of-flight measurements and test particle simulations to constrain the ions' origin are used. After being validated, the detection method is applied to all the flybys for which the CAPS/IMS instrument gathered valid data, constraining the region around the moon where the signatures are observed. The results reveal an escape region located in the anti-Saturn direction as expected from the nominal corotation electric field direction. These findings provide new constraints for the area of freshly produced pickup ion escape, giving an approximate escape rate of inline image ions· s−1

Micron-sized atom traps made from magneto-optical thin films

We have produced magnetic patterns suitable for trapping and manipulating neutral atoms on a $1 \mu$m length scale. The required patterns are made in Co/Pt thin films on a silicon substrate, using the heat from a focussed laser beam to induce controlled domain reversal. In this way we draw lines and "paint" shaped areas of reversed magnetization with sub-micron resolution. These structures produce magnetic microtraps above the surface that are suitable for holding rubidium atoms with trap frequencies as high as ~1 MHz.Comment: 6 pages, 7 figure