Rosetta-Alice Observations of Exospheric Hydrogen and Oxygen on Mars

The European Space Agency's Rosetta spacecraft, en route to a 2014 encounter with comet 67P/Churyumov-Gerasimenko, made a gravity assist swing-by of Mars on 25 February 2007, closest approach being at 01:54UT. The Alice instrument on board Rosetta, a lightweight far-ultraviolet imaging spectrograph optimized for in situ cometary spectroscopy in the 750-2000 A spectral band, was used to study the daytime Mars upper atmosphere including emissions from exospheric hydrogen and oxygen. Offset pointing, obtained five hours before closest approach, enabled us to detect and map the HI Lyman-alpha and Lyman-beta emissions from exospheric hydrogen out beyond 30,000 km from the planet's center. These data are fit with a Chamberlain exospheric model from which we derive the hydrogen density at the 200 km exobase and the H escape flux. The results are comparable to those found from the the Ultraviolet Spectrometer experiment on the Mariner 6 and 7 fly-bys of Mars in 1969. Atomic oxygen emission at 1304 A is detected at altitudes of 400 to 1000 km above the limb during limb scans shortly after closest approach. However, the derived oxygen scale height is not consistent with recent models of oxygen escape based on the production of suprathermal oxygen atoms by the dissociative recombination of O2+.Comment: 17 pages, 8 figures, accepted for publication in Icaru

Entwicklung von Rückbau- und Recyclingstandards für Rotorblätter : Abschlussbericht [Kurztitel: Aufbereitung von Rotorblättern]

Als Ergebnis der breiten politischen Befürwortung für die Energiewende und des stetig wachsenden Bestands an Windenergieanlagen (WEA) in Deutschland und Europa gewinnen Fragen der Wartung, Laufzeitverlängerung sowie des Anlagenrückbaus und Recyclings an Bedeutung. Eine besondere Herausforderung stellt dabei das Rotorblattrecycling mit ihren glasfaserverstärkten (GFK) und carbonfaserverstärkten (CFK) Anlagenteilen dar. Die für diese Materialien existierenden Recyclingprozesse haben sich noch nicht durchgesetzt und der Wiedereinsatz der recyclierten Materialien ist in der Breite nicht etabliert. Weiterhin mangelt es an Standards für die Demontage und werkstoffliche Aufbereitung dieser Materialien. Zentraler Forschungsgegenstand war die Entwicklung von Standards für eine möglichst hochwertige und gleichzeitig wirtschaftlich zumutbare Aufbereitungs- und Behandlungsstrategie für Rotorblätter. Ausgehend von den zu erwartenden Abfallmengen und - arten und des speziellen Aufbaus und der Zusammensetzung der verschiedenen Rotorblätter wurde ein vollständiges und schlüssiges Konzept für deren Wartungen, Reparatur, Demontage, Vorzerkleinerung und Aufbereitung erarbeitet. Darauf basierend wurde die Organisationsverantwortung aus rechtlicher Sicht geprüft und mögliche erforderlicher, ergänzender materiell-rechtlicher Vorgaben vorgeschlagen. Auch Elemente der abfallwirtschaftlichen Produktverantwortung wurden auf Zweckmäßigkeit geprüft und bewertet. Die Studie beschreibt damit ein erstes umfassendes technisches, rechtliches und organisatorisches Recyclingkonzept für Rotorblätter

Ultraviolet observations of coronal mass ejection impact on comet 67P/Churyumov-Gerasimenko by Rosetta Alice

The Alice ultraviolet spectrograph on the European Space Agency Rosetta spacecraft observed comet 67P/Churyumov–Gerasimenko in its orbit around the Sun for just over two years. Alice observations taken in 2015 October, two months after perihelion, show large increases in the comet's Lyβ, O i 1304, O i 1356, and C i 1657 Å atomic emission that initially appeared to indicate gaseous outbursts. However, the Rosetta Plasma Consortium instruments showed a coronal mass ejection (CME) impact at the comet coincident with the emission increases, suggesting that the CME impact may have been the cause of the increased emission. The presence of the semi-forbidden O i 1356 Å emission multiplet is indicative of a substantial increase in dissociative electron impact emission from the coma, suggesting a change in the electron population during the CME impact. The increase in dissociative electron impact could be a result of the interaction between the CME and the coma of 67P or an outburst coincident with the arrival of the CME. The observed dissociative electron impact emission during this period is used to characterize the O2 content of the coma at two peaks during the CME arrival. The mechanism that could cause the relationship between the CME and UV emission brightness is not well constrained, but we present several hypotheses to explain the correlation

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object

After flying past Pluto in 2015, the New Horizons spacecraft shifted course to encounter (486958) 2014 MU69, a much smaller body about 30 kilometers in diameter. MU69 is part of the Kuiper Belt, a collection of small icy bodies orbiting in the outer Solar System. Stern et al. present the initial results from the New Horizons flyby of MU69 on 1 January 2019. MU69 consists of two lobes that appear to have merged at low speed, producing a contact binary. This type of Kuiper Belt object is mostly undisturbed since the formation of the Solar System and so will preserve clues about that process.Science, this issue p. eaaw9771INTRODUCTIONThe Kuiper Belt is a broad, torus-shaped region in the outer Solar System beyond Neptune’s orbit. It contains primordial planetary building blocks and dwarf planets. NASA’s New Horizons spacecraft conducted a flyby of Pluto and its system of moons on 14 July 2015. New Horizons then continued farther into the Kuiper Belt, adjusting its trajectory to fly close to the small Kuiper Belt object (486958) 2014 MU69 (henceforth MU69; also informally known as Ultima Thule). Stellar occultation observations in 2017 showed that MU69 was ~25 to 35 km in diameter, and therefore smaller than the diameter of Pluto (2375 km) by a factor of ~100 and less massive than Pluto by a factor of ~106. MU69 is located about 1.6 billion kilometers farther from the Sun than Pluto was at the time of the New Horizons flyby. MU69’s orbit indicates that it is a “cold classical” Kuiper Belt object, thought to be the least dynamically evolved population in the Solar System. A major goal of flying past this target is to investigate accretion processes in the outer Solar System and how those processes led to the formation of the planets. Because no small Kuiper Belt object had previously been explored by spacecraft, we also sought to provide a close-up look at such a body’s geology and composition, and to search for satellites, rings, and evidence of present or past atmosphere. We report initial scientific results and interpretations from that flyby.RATIONALEThe New Horizons spacecraft completed its MU69 flyby on 1 January 2019, with a closest approach distance of 3538 km—less than one-third of its closest distance to Pluto. During the high-speed flyby, made at 14.4 km s-1, the spacecraft collected ~50 gigabits of high-resolution imaging, compositional spectroscopy, temperature measurements, and other data on this Kuiper Belt object. We analyzed the initial returned flyby data from the seven scientific instruments carried on the spacecraft: the Ralph multicolor/panchromatic camera and mapping infrared composition spectrometer; the Long Range Reconnaissance Imager (LORRI) long–focal length panchromatic visible imager; the Alice extreme/far ultraviolet mapping spectrograph; the Radio Experiment (REX); the Solar Wind Around Pluto (SWAP) solar wind detector; the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) high-energy charged particle spectrometer; and the Venetia Burney Student Dust Counter (VBSDC), a dust impact detector.RESULTSImaging of MU69 showed it to be a bilobed, contact binary. MU69’s two lobes appear to have formed close to one another, becoming an orbiting pair that subsequently underwent coupled tidal and orbital evolution to merge into the contact binary we observe today. The object rotates on its axis every 15.92 hours; its rotation pole is inclined approximately 98° to the plane of its heliocentric orbit. Its entire surface has a low visible-wavelength reflectivity (albedo) but displays brighter and darker regions across its surface, ranging from 5 to 12% reflectivity. The brightest observed regions are the “neck” of MU69, where the two lobes are joined, and two discrete bright spots inside the largest crater-like feature on the object’s surface. Although MU69’s albedo varies substantially across its surface, it is uniformly red in color, with only minor observed color variations. This coloration likely represents a refractory residue from ices and organic molecules processed by ultraviolet light and cosmic rays. Spectra of the surface revealed tentative absorption band detections due to water ice and methanol. The geology of MU69 consists of numerous distinct units but shows only a small number of craters, providing evidence that there is a deficit of Kuiper Belt objects smaller than ~1 km in diameter, and that there is a comparatively low collision rate in its Kuiper Belt environment compared to what would be expected in a collisional equilibrium population. A three-dimensional shape model derived from the images shows MU69 is not simply elongated but also flattened. The larger lobe was found to be lenticular, with dimensions of approximately 22 × 20 × 7 km (uncertainty <0.6 × 1 × 2 km), whereas the smaller lobe is less lenticular, with dimensions of approximately 14 × 14 × 10 km (uncertainty <0.4 × 0.7 × 3 km). No evidence of satellites, rings, or an extant atmosphere was found around MU69.CONCLUSIONBoth MU69’s binarity and unusual shape may be common among similarly sized Kuiper Belt objects. The observation that its two lobes are discrete, have retained their basic shapes, and do not display prominent deformation or other geological features indicative of an energetic or disruptive collision indicates that MU69 is the product of a gentle merger of two independently formed bodies.Image of MU69 from New Horizons LORRI observations taken 1 January 2019.The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69’s origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes