Chemistry and accretion history of Mars

1994 ◽  
Vol 349 (1690) ◽  
pp. 285-293 ◽  
Keyword(s):  
Bulk Composition ◽  
Volcanic Gases ◽  
Martian Surface ◽  
Volatile Elements ◽  
Water Ice ◽  
The Earth ◽  
History Of ◽  
The Mean ◽  
Wet Climate ◽  
Martian Regolith

Using element correlations observed in SNC meteorites and general cosmochemical constraints, Wänke & Dreibus (1988) have estimated the bulk composition of Mars. The mean abundance value for moderately volatile elements Na, P, K, F, and Rb and most of the volatile elements like Cl, Br, and I in the Martian mantle exceed the terrestrial values by about a factor of two. The striking depletion of all elements with chalcophile character (Cu, Co, Ni, etc.) indicates that Mars, contrary to the Earth, accreted homogeneously, which also explains the obvious low abundance of water and carbon. SNC meteorites and especially the shergottites are very dry rocks, they also contain very little carbon, while the concentrations of chlorine and especially sulphur are higher than those in terrestrial rocks. As a consequence we should expect SO 2 and HC1 to be the most abundant compounds in Martian volcanic gases. This might explain the dominance of sulphur and chlorine in the Viking soils. In turn SO 2 , being an excellent greenhouse gas, may have been of major importance for the warm and wet period in the ancient Martian history. Episodic release of larger quantities of SO 2 stored in liquid or solid SO 2 tables in the Martian regolith triggered by volcanic intrusions as suggested here could lead to a large number of warm and wet climate periods of the order of a hundred years, interrupted by much longer cold periods characterized by water ice and liquid of solid SO 2 . Sulphur (FeS) probably also governs the oxygen fugacity of the Martian surface rocks.

Chemical composition and accretion history of terrestrial planets

1988 ◽  
Vol 325 (1587) ◽  
pp. 545-557 ◽  
Keyword(s):  
Bulk Composition ◽  
Parent Body ◽  
Conclusive Evidence ◽  
Martian Surface ◽  
Volatile Elements ◽  
The Earth ◽  
Material Component ◽  
History Of ◽  
Siderophile Elements ◽  
High Concentrations

The high concentrations of moderately siderophile elements (Ni, Co, etc.) in the Earth’s mantle and the similarity of their Cl normalized abundances to those of moderately volatile elements (F, Na, K, Rb) and some elements such as In, which under solar nebula conditions are highly volatile, are striking. To account for the observed abundances, inhomogeneous accretion of the Earth from two components has been proposed. In this model accretion started with the highly reduced component A devoid of all elements more volatile than Na, followed by accretion of more and more oxidized material (component B), containing all elements in Cl abundances. Recent observations have brought almost conclusive evidence that SNC meteorites are martian surface rocks ejected by huge impacts. By assuming that Mars is indeed the parent body of SNC meteorites, the bulk composition of Mars is estimated. The data on the composition of Mars obtained in this way clearly show that the two-component model is also valid for Mars. The striking depletion of all elements with chalcophile character in the martian mantle indicates that, contrary to the Earth, Mars accreted almost homogeneously (H. Wanke, Phil. Trans. R. Soc. Lond . A 303, 287 (1981)).

Constitution of terrestrial planets

1981 ◽  
Vol 303 (1477) ◽  
pp. 287-302 ◽  
Keyword(s):  
Bulk Composition ◽  
Parent Body ◽  
The Moon ◽  
Volatile Elements ◽  
Earth’S Mantle ◽  
The Earth ◽  
History Of ◽  
Relationship Of ◽  
Reduced State

Reliable estimates of the bulk composition are so far restricted to the three planetary objects from which we have samples for laboratory investigation, i.e. the Earth, the Moon and the eucrite parent asteroid. The last, the parent body of the eucrite— diogenite family of meteorites, an object that like Earth and Moon underwent magmatic differentiations, seems to have an almost chondritic composition except for a considerable depletion of all moderately volatile (Na, K, Rb, F, etc.) and highly volatile (Cl, Br, Cd, Pb, etc.) elements. The Moon is also depleted in moderately volatile and volatile elements compared to carbonaceous chondrites of type 1 (Cl) and also compared to the Earth. Again normalized to Cl and Si the Earth’s mantle and the Moon are slightly enriched in refractory lithophile elements and in magnesium. It might be that this enrichment is fictitious and only due to the normalization to Si and that both Earth’s mantle and Moon are depleted in Si, which partly entered the Earth’s core in metallic form. The striking depletion of the Earth’s mantle for the elements V, Cr and Mn can also be explained by their partial removal into the core. The similar abundances of V, Cr and Mn in the Moon and in the Earth’s mantle indicate the strong genetic relationship of Earth and Moon. Apart from their contents of metallic iron, all siderophile elements, moderately volatile and volatile elements, Earth and Moon are chemically very similar. It might well be that, with these exceptions and that of a varying degree of oxidation, all the inner planets have a similar chemistry. The chemical composition of the Earth’s mantle, for which reliable and accurate data have recently been obtained from the study of ultramafic nodules, yields important information about the accretion history of the Earth and that of the inner planets. It seems that accretion started with highly reduced material, with all Fe as metal and even Si and Cr, V and Mn partly in reduced state, followed by the accretion of more and more oxidized matter.

scholarly journals XVIII. On the fossil Elk of Ireland

1825 ◽  
Vol 115 ◽  
pp. 429-435
Keyword(s):  
Royal College ◽  
The West ◽  
The North ◽  
Royal Dublin Society ◽  
The Earth ◽  
History Of ◽  
The Subject ◽  
The Mean ◽  
Additional Value ◽  
Mean Time

Notwithstanding the frequent occurrence of the remains of the gigantic elk in Ireland, it is remarkable that precise accounts should not have been kept of all the peculiar cir­cumstances under which they occur entombed in its super­ficial strata. To obtain an opportunity of examining these relations had long been my desire; and as fortunately, dur­ing my avocations last autumn in the north of Ireland, a discovery came to my knowledge that seemed likely to throw light on the subject, I proceeded to its investigation, intending, should the results be found deserving of attention, to place them on record. These results have proved the more interesting, as they apparently lead to the conclusion, that this magnificent animal lived in the countries in which its remains are now found, at a period of time which, in the history of the earth, can be considered only as modern. I had advanced thus far when I became apprized of an analogous discovery made last year in the west of Ireland by the Rev. W . Wray Maunsell, Archdeacon of Limerick; which is not only confirmative of my own experience, but has the additional value of embracing particulars not hitherto noticed by any other observer. Mr. Maunseli's researches, elucidated by the able assistance of Mr. John Hart, Member of the Royal College of Surgeons, have been communicated from time to time to the Royal Dublin Society in the form of letters, and have been entered upon their minutes; and, it is to be hoped, that a distinct publication on the subject may hereafter appear, illustrated by a description of the splendid specimen of the skeleton of the animal now deposited by the liberality of the Reverend Archdeacon in the museum of that Society. In the mean time I propose, after giving a concise account of my own inquiries, to refer briefly to the more prominent points in Mr. Maunseli's discoveries, in as far as they bear immediately on the question of the ancient or modern origin of those remains.

The motion of a lunar orbiter

1966 ◽  
Vol 25 ◽  
pp. 373
Author(s):  
Y. Kozai
Keyword(s):  
Degrees Of Freedom ◽  
Dimensional Space ◽  
Artificial Satellite ◽  
Equations Of Motion ◽  
Triaxial Ellipsoid ◽  
The Moon ◽  
Secular Motion ◽  
The Earth ◽  
Close Satellite ◽  
The Mean

The motion of an artificial satellite around the Moon is much more complicated than that around the Earth, since the shape of the Moon is a triaxial ellipsoid and the effect of the Earth on the motion is very important even for a very close satellite.The differential equations of motion of the satellite are written in canonical form of three degrees of freedom with time depending Hamiltonian. By eliminating short-periodic terms depending on the mean longitude of the satellite and by assuming that the Earth is moving on the lunar equator, however, the equations are reduced to those of two degrees of freedom with an energy integral.Since the mean motion of the Earth around the Moon is more rapid than the secular motion of the argument of pericentre of the satellite by a factor of one order, the terms depending on the longitude of the Earth can be eliminated, and the degree of freedom is reduced to one.Then the motion can be discussed by drawing equi-energy curves in two-dimensional space. According to these figures satellites with high inclination have large possibilities of falling down to the lunar surface even if the initial eccentricities are very small.The principal properties of the motion are not changed even if plausible values ofJ3andJ4of the Moon are included.This paper has been published in Publ. astr. Soc.Japan15, 301, 1963.

Revisiting the Natural History of Chronic Scaphoid Nonunions: A Retrospective Study of 20 Cases

2021 ◽  
Author(s):  
J. Terrence Jose Jerome
Keyword(s):  
Retrospective Study ◽  
Natural History ◽  
Functional Outcome ◽  
Grip Strength ◽  
Scaphoid Nonunion ◽  
Proximal Pole ◽  
Degenerative Arthritis ◽  
Level Of Evidence ◽  
History Of ◽  
The Mean

Abstract Background The natural history of scaphoid nonunion is the development of degenerative arthritis. A lot of information is still unclear about this progression. The purpose of this study is to analyze patients with scaphoid nonunions who had not received any kind of treatment and to assess the functional outcome. Materials and Methods This is a retrospective study that analyzed the patients with chronic scaphoid nonunions between 2009 and 2019. None of the patients received any treatment. The age at the time of injury, examination, pattern of fracture, types of scaphoid nonunion, symptoms, and duration of nonunion were noted. Diagnosis was confirmed by radiographs, computed tomography (CT) scan, and magnetic resonance imaging (MRI). Scapholunate and radiolunate angles were recorded. Pain score, modified mayo wrist score, grip strength, range of movement, and the functional outcome of these scaphoid nonunions were analyzed. A statistical correlation between the scaphoid nonunion presentations and the functional outcome was assessed. Results The mean age of the patients was 62 years (range: 35–82 years.). There were 17 male and 3 female patients. There were 9 waist and 11 proximal pole scaphoid nonunions. The mean duration of scaphoid nonunion was 34 years (range: 10–62 years). None of the patients had avascular necrosis (AVN) of the proximal scaphoid. The age at examination, gender, side of injury, fracture pattern (waist/proximal pole), fracture displacement ≤ 1 mm or > 1 mm, nonunion duration, and radiographic arthritic parameters had no significant impact on the functional outcome. Conclusions Untreated chronic scaphoid nonunion leads to the development of degenerative arthritis over a period of years, which is still unpredictable. Most of the patients become aware of the nonunion following a precedent injury or other reasons. Most of the patients have fair/good functional outcome despite reduced range of movements and grip strength. Many do not favor surgical intervention in the course of nonunion. Chronic nonunions open a lot of unanswered questions. Clinical relevance There have been numerous studies on the treatment aspects of scaphoid nonunion, with little knowledge about certain people with nonunion who did not have any kind of treatment. The demographics, clinical findings, and radiological parameters do confirm the progression of these nonunion to arthritis, but most of them had fair-to-good outcome throughout their life. It opens our thinking about the real need of treatment in such nonunions and raises numerous questions about the disease. Level of evidence This is a Level IV study.

George Hoggart Toulmin: politics and geology

1978 ◽  
Vol 8 (4) ◽  
pp. 481-481
Author(s):  
ROY PORTER
Keyword(s):  
French Revolution ◽  
Social Order ◽  
Lower Class ◽  
Great Distance ◽  
The Earth ◽  
Christian View ◽  
The Social ◽  
French Enlightenment ◽  
Political Conservatism ◽  
History Of

The physician George Hoggart Toulmin (1754–1817) propounded his theory of the Earth in a number of works beginning with The antiquity and duration of the world (1780) and ending with his The eternity of the universe (1789). It bore many resemblances to James Hutton's "Theory of the Earth" (1788) in stressing the uniformity of Nature, the gradual destruction and recreation of the continents and the unfathomable age of the Earth. In Toulmin's view, the progress of the proper theory of the Earth and of political advancement were inseparable from each other. For he analysed the commonly accepted geological ideas of his day (which postulated that the Earth had been created at no great distance of time by God; that God had intervened in Earth history on occasions like the Deluge to punish man; and that all Nature had been fabricated by God to serve man) and argued they were symptomatic of a society trapped in ignorance and superstition, and held down by priestcraft and political tyranny. In this respect he shared the outlook of the more radical figures of the French Enlightenment such as Helvétius and the Baron d'Holbach. He believed that the advance of freedom and knowledge would bring about improved understanding of the history and nature of the Earth, as a consequence of which Man would better understand the terms of his own existence, and learn to live in peace, harmony and civilization. Yet Toulmin's hopes were tempered by his naturalistic view of the history of the Earth and of Man. For Time destroyed everything — continents and civilizations. The fundamental law of things was cyclicality not progress. This latent political conservatism and pessimism became explicit in Toulmin's volume of verse, Illustration of affection, published posthumously in 1819. In those poems he signalled his disapproval of the French Revolution and of Napoleonic imperialism. He now argued that all was for the best in the social order, and he abandoned his own earlier atheistic religious radicalism, now subscribing to a more Christian view of God. Toulmin's earlier geological views had run into considerable opposition from orthodox religious elements. They were largely ignored by the geological community in late eighteenth and early nineteenth century Britain, but were revived and reprinted by lower class radicals such as Richard Carlile. This paper is to be published in the American journal, The Journal for the History of Ideas in 1978 (in press).

Computers in Geology - 25 Years of Progress

1994 ◽  
Keyword(s):  
Computer Modeling ◽  
Quantitative Methods ◽  
State Of The Art ◽  
International Association ◽  
Mathematical Geology ◽  
25Th Anniversary ◽  
The Earth ◽  
Wide Range ◽  
History Of ◽  
Mapping Techniques

This volume vividly demonstrates the importance and increasing breadth of quantitative methods in the earth sciences. With contributions from an international cast of leading practitioners, chapters cover a wide range of state-of-the-art methods and applications, including computer modeling and mapping techniques. Many chapters also contain reviews and extensive bibliographies which serve to make this an invaluable introduction to the entire field. In addition to its detailed presentations, the book includes chapters on the history of geomathematics and on R.G.V. Eigen, the "father" of mathematical geology. Written to commemorate the 25th anniversary of the International Association for Mathematical Geology, the book will be sought after by both practitioners and researchers in all branches of geology.

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