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Comet dust tail analysis using the Finson-Probstein model
Qasim Afghan
Mullard Space Science Laboratory, UCL, Surrey, UK
Using a novel analysis method, the fine-structure detail of comet dust tails is analysed from amateur and professional comet images. Given the date and time of the image taken, the comet’s position in the sky is calculated using an open source algorithm [1] and the comet’s dust tail is simulated for that position and time using the Finson-Probstein model. This modeled dust tail structure is then projected and overlaid onto the comet image to directly compare the theoretical and real structure of several comet’s dust tails, with the aim of identifying similarities and discrepancies between the model and the image.
This is a continuation of the work done previously on Comet McNaught, which ultimately led to the discovery of new fine-scale structure features in the comet’s dust tail [2]. This model is now applied to several other comets, including Comet C/2004 F4 Bradfield, to find similar fine-scale structures and to highlight this model’s utility in comet dust analysis.
Finally, this work will be put into context as the first step in the development of an automated analysis method for analysing cometary dust and ion tails. This automated analysis method is in preparation for the upcoming opening of the Vera Reuben Observatory (formerly known as ‘LSST’), and aims to automatically identify comet tail structures from the Observatory’s stream of comet images.
[1] https://doi.org/10.1088/0004-6256/139/5/1782
[2] https://doi.org/10.1016/j.icarus.2018.09.013
Different types of spinel symplectites in lunar dunite 72415 and 72417
Krishan Bhanot
Dept. of Earth and Planetary Sciences, Birkbeck, University of London, Malet St. London, WC1E 7HX, UK
Dept. of Earth Sciences, Natural History Museum, Cromwell Rd, London, SW7 5BD, UK
Symplectites are intergrowths of two or more minerals that occur because of a change in temperature and/or pressure. Therefore, they can tell us about the history of a rock sample from any planetary body. Spinel symplectites have been reported in lunar dunites from the Apollo 17 mission to the Taurus–Littrow valley. Samples 72415 to 72418 were taken from a 10 cm size clast from boulder 3, station 2. Sample 72417 yielded an age of 4.55 ± 0.1 Ga. Hand specimens are brecciated and composed of pale-green, translucent olivine grains up to 10 mm in size, set in a fine-grained matrix. We have investigated Apollo 17 samples 72415,4 and 72417,9003 by electron microprobe analysis (TS 72415,53) and micro-CT.
Artemis and Actaeon: transforming a Moon treaty into international accords
Mukesh Chiman BHATT
School of Law, Birkbeck, University of London, UK
Continuing proposals for permanent present on or near the Moon after the Apollo landings raise questions of legitimacy, a discussion that itself has continued for over 50 years. National and geopolitical interests play a large part in adherence to and compliance with the Outer Space Treaty and its adjunct, the Moon Treaty. Apart from ratification and entry into force, new questions have arisen: the ethics of inhabiting a celestial body that has influenced cultures on Earth, the necessity of retaining pristine environments off-Earth, and the economic viability of settlements and mineral resources. Added are issues of said legitimacy for these activities, of covert militarisation, and of seeding a sterile environment with life, whether as ark or as biosphere. What is clear is the international community has differing approaches in deciding its answers. This paper will examine new and various mechanisms that allow resolution to these conundrums, by providing an overview of historical development of space law in short form, followed by the major considerations that may allow such conventions and agreements to be circumvented whilst remaining within the spirit of international law paradigm.
Keywords: Moon treaty, space law, legal mechanisms, ethics, law
Petrology and oxygen isotopes in new enstatite chondrite fragments from the Almahata Sitta fall: Implications for the nature of “Theia”?
Hilary Downes
Dept. of Earth and Planetary Science, Birkbeck University of London, Malet St, London WC1E 7HX, UK (h.downes@ucl.ac.uk)
Dept. of Earth Sciences, Natural History Museum, Cromwell Rd, London SW7 5BD, UK
Enstatite chondrites are important varieties of meteorites because they have identical isotopic compositions to those of the Earth and Moon. The possibility that the Moon-forming Giant Impactor “Theia” has been discussed in several recent studies. The fall of Asteroid 2008 TC3 in Sudan in 2008 gives an opportunity to investigate very fresh (unweathered) extraterrestrial material. Most of the meteorite fragments found in the strewn field resulting from the fall were ureilites but a high proportion (20-30%) are other varieties of meteorites, including many enstatite chondrites. We have investigated 5 new enstatite chondrite fragments from the fall (known as the Almahata Sitta meteorite) for texture, mineralogy, mineral compositions, and oxygen isotopes. These pristine samples enable us to constrain the range of oxygen isotopes shown by the enstatite chondrite parent body/ies.
Longitudinal ridges in two lunar long runout landslides, the Apollo 17 light mantle avalanche and the Tsiolkovskiy Crater landslide: Linking morphological features to landslide dynamics
Giulia Magnarini
Department of Earth Sciences, University College London
On the Moon, mass wasting processes are mainly reported on the inner steep slopes of impact craters [1]. These events involve dry granular material, from regolith size to boulder size, and they occur in vacuum and in the absence of liquid water. However, since the early orbital observations of the Moon from the Lunar Orbiter mission and during the Apollo programme, two unusually long runout landslides have been also observed: the Light Mantle avalanche in the Taurus-Littrow Valley [2] and the Tsiolkovskiy crater landslide, on the far side[2][3]. These are the only cases of long runout landslides known on the Moon. Their uniqueness has intrigued researchers, for the origin of the reduction of friction required to explain their mobility remains unknown on a dry, airless body.
Their different morphological aspects bear differences in their formation processes, which include preparatory and triggering factors, and modality of transport. However, both landslide deposits are marked by longitudinal linear pattern. These distinctive structures are common in large-scale mass movements across the Solar System and their presence has always been intuitively associated with high-speed flows [4] and tentatively to the presence of a basal icy surface [5].
Alternatively, the finding of a scaling relationship between the wavelength of the longitudinal ridges and the thickness of the deposit for a martian long runout landslide [6] support the hypothesis that mechanical instabilities within the rapid moving slide are responsible for the formation of longitudinal ridges [7], regardless of environmental conditions.
Following recent work by [6], we decided to conduct morphological analysis of the Apollo 17 Light Mantle avalanche deposit and the Tsiolkovskiy crater landslide deposit in order to assess whether the same scaling relationship between the wavelength of longitudinal ridges and the thickness of the deposit is recurring in lunar long runout landslides. We here present the initial results from such morphometric analysis and discuss their possible implications.
REFERENCES:
[1] Kokelaar et al. (2017) JGR Planets, 122, 1893–1925, [2] El-Baz F. (1972) Proceedings Lun. Plan. Conf., 1, 39-61, [3] Guest & Murray (1969) Planet Space Sci., 17, 121, [4] Lucchitta B.K. (1979) JGR, 84, 8097-8113, [5] De Blasio F.V. (2011) Planet. Space Sci., 59, 1384-1392, [6] Magnarini et al. (2019) Nat. Commun., 10, 4711, [7] Börzsönyi et al. (2009) Phys. Rev. Lett., 103, 178302.
Exploring non-LTE effects in Exoplanet atmospheres
Samuel Wright
Department of Physics and Astronomy, UCL
Great advances have been made over the last few decades in probing the atmospheres of extra-solar planets, enabling us to further constrain the conditions that exist on these worlds. When modelling these atmospheres however, the work done to date has assumed that the species present are in local thermodynamic equilibrium (LTE). It is known, for instance on Earth, that non-LTE effects are present in the atmosphere and give rise to varying spectra; work already conducted by the community has expanded the remote sensing of non-LTE to other planets within our solar system. This poster presents a preliminary exploration into non-LTE effects in exoplanet atmospheres, showing the differences that arise in some notable molecular spectra due to these effects. An initial evaluation of the detectability of these differences by next generation space telescopes is presented, along with some indicative forward models and initial retrievals. Further work will involve further exploring atmospheric retrieval of non-LTE effects and instrument simulations.