scholarly journals On the attempts to measure water (and other volatiles) directly at the surface of a comet

2017 ◽  
Vol 375 (2094) ◽  
pp. 20150385 ◽  
Author(s):  
I. P. Wright ◽  
S. Sheridan ◽  
G. H. Morgan ◽  
S. J. Barber ◽  
A. D. Morse
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Solar System ◽  
Space Mission ◽  
Daily Cycles ◽  
Surface Measurements ◽  
Comet 67P ◽  
Do So

The Ptolemy instrument on the Philae lander (of the Rosetta space mission) was able to make measurements of the major volatiles, water, carbon monoxide and carbon dioxide, directly at the surface of comet 67P/Churyumov–Gerasimenko. We give some background to the mission and highlight those instruments that have already given insights into the notion of water in comets, and which will continue to do so as more results are either acquired or more fully interpreted. On the basis of our results, we show how comets may in fact be heterogeneous over their surface, and how surface measurements can be used in a quest to comprehend the daily cycles of processes that affect the evolution of comets. This article is part of the themed issue ‘The origin, history and role of water in the evolution of the inner Solar System’.

scholarly journals Common origins and the ethics of planetary seeding

2016 ◽  
Vol 15 (4) ◽  
pp. 301-306 ◽  
Author(s):  
Tony Milligan
Keyword(s):  
Solar System ◽  
Practical Wisdom ◽  
Thought Experiment ◽  
Ethical Reason ◽  
Microbial Life ◽  
Historical Justice ◽  
Do So

AbstractFaced with a choice between attempting to seed another world with terrestrially-sourced microbes (with which we would have a shared origin) and microbes sourced from elsewhere within the solar system (whose origins might therefore differ), would we have any non-instrumental ethical reason to favour the terrestrial microbes? What follows will argue that in relation to the goals of promoting life similar to our own, or even simply microbial life, we might conceivably make such an appeal and do so in a defensible manner. However, in no case would such a consideration operate as a silencer for rival considerations (such as likelihood of success, enhancing diversity or historical justice). The thought experiment serves to highlight the diversity of considerations which are in play in ethical deliberation about matters of astrobiology and the role of practical wisdom rather than trumping considerations.

scholarly journals Rosetta CONSERT Data as a Testbed for In Situ Navigation of Space Probes and Radiosciences in Orbit/Escort Phases for Small Bodies of the Solar System

2021 ◽  
Vol 13 (18) ◽  
pp. 3747
Author(s):  
Mao Ye ◽  
Fei Li ◽  
Jianguo Yan ◽  
Alain Hérique ◽  
Wlodek Kofman ◽  
...  
Keyword(s):  
Solar System ◽  
Real Time ◽  
Autonomous Navigation ◽  
Space Mission ◽  
Observation Time ◽  
Small Bodies ◽  
Tracking Station ◽  
Future Space ◽  
Comet 67P

Many future space missions to asteroids and comets will implement autonomous or near-autonomous navigation, in order to save costly observation time from Earth tracking stations, improve the security of spacecraft and perform real-time operations. Existing Earth-Spacecraft-Earth tracking modes rely on severely limited Earth tracking station resources, with back-and-forth delays of up to several hours. In this paper, we investigate the use of CONSERT ranging data acquired in direct visibility between the lander Philae and the Rosetta orbiter, in the frame of the ESA space mission to comet 67P/Churyumov-Gerasimenko, as a proxy of autonomous navigation and orbitography science capability.

scholarly journals Biofuels from Micro-Organisms: Thermodynamic Considerations on the Role of Electrochemical Potential on Micro-Organisms Growth

2021 ◽  
Vol 11 (6) ◽  
pp. 2591
Author(s):  
Umberto Lucia ◽  
Giulia Grisolia
Keyword(s):  
Carbon Dioxide ◽  
Temperature Effect ◽  
Open Problem ◽  
Electric Potential ◽  
Present Model ◽  
Electrochemical Potential ◽  
Micro Organisms ◽  
Carbon Dioxide Mitigation ◽  
Do So

Biofuels from micro-organisms represents a possible response to the carbon dioxide mitigation. One open problem is to improve their productivity, in terms of biofuels production. To do so, an improvement of the present model of growth and production is required. However, this implies an understanding of the growth spontaneous conditions of the bacteria. In this paper, a thermodynamic approach is developed in order to highlight the fundamental role of the electrochemical potential in bacteria proliferation. Temperature effect on the biosystem behaviour has been pointed out. The results link together the electrochemical potential, the membrane electric potential, the pH gradient through the membrane, and the temperature, with the result of improving the thermodynamic approaches, usually introduced in this topic of research.

scholarly journals From chemical metabolism to life: the origin of the genetic coding process

2017 ◽  
Vol 13 ◽  
pp. 1119-1135 ◽  
Author(s):  
Antoine Danchin
Keyword(s):  
Carbon Dioxide ◽  
Amino Acids ◽  
Solar System ◽  
Genetic Code ◽  
Metabolic Pathways ◽  
Origins Of Life ◽  
Genetic Coding ◽  
Carbon Molecules ◽  
Carry Over

Looking for origins is so much rooted in ideology that most studies reflect opinions that fail to explore the first realistic scenarios. To be sure, trying to understand the origins of life should be based on what we know of current chemistry in the solar system and beyond. There, amino acids and very small compounds such as carbon dioxide, dihydrogen or dinitrogen and their immediate derivatives are ubiquitous. Surface-based chemical metabolism using these basic chemicals is the most likely beginning in which amino acids, coenzymes and phosphate-based small carbon molecules were built up. Nucleotides, and of course RNAs, must have come to being much later. As a consequence, the key question to account for life is to understand how chemical metabolism that began with amino acids progressively shaped into a coding process involving RNAs. Here I explore the role of building up complementarity rules as the first information-based process that allowed for the genetic code to emerge, after RNAs were substituted to surfaces to carry over the basic metabolic pathways that drive the pursuit of life.

The role of isocitrate lyase in the metabolism of algae

1966 ◽  
Vol 166 (1002) ◽  
pp. 11-29 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Soluble Fraction ◽  
Isocitrate Lyase ◽  
Tricarboxylic Acid Cycle ◽  
Glyoxylate Cycle ◽  
Tricarboxylic Acid ◽  
Chlamydomonas Reinhardii ◽  
The Glyoxylate Cycle ◽  
Do So

The incorporation of isotope from [2- 14 C]ethanol by cultures of the Brannon no. 1 strain of Chlorella vulgaris , growing on ethanol aerobically in the dark, was consistent with the operation of the tricarboxylic acid and glyoxylate cycles. Results obtained with [l- 14 C]acetate, added to similar cultures growing on glucose in the dark or on carbon dioxide in the light, indicated that the glyoxylate cycle did not function under these conditions. However, one of the key enzymes of this cycle, isocitrate lyase, was present in large amounts in extracts of this organism under all conditions of growth; in contrast, isocitrate lyase was inducibly formed by Chlamydomonas reinhardii prior to growth on acetate. No obvious dysfunction of the tricarboxylic acid cycle, which might necessitate the activity of isocitrate lyase during growth on other than C 2 -compounds, was detected in the Brannon no. 1 strain, nor were differences observed between the properties of the enzyme purified from cells grown on acetate and on glucose. But, whereas isocitrate lyase was wholly found in a soluble fraction of the organism after growth on glucose or on carbon dioxide, acetate-grown cells contained a major portion of their isocitrate lyase in a dense, particulate fraction. The Brannon no. 1 strain of Chlorella excreted labelled glycollate during growth in the dark on glucose in the presence of sodium [ 14 C]bicarbonate, but ceased to do so after transfer to acetate growth medium. The Pearsall’s strain of Chlorella , which does not form isocitrate lyase during growth on glucose, did not excrete labelled glycollate under these conditions. These results suggest that the Brannon no. 1 strain of Chlorella contained an active isocitrate lyase under all conditions of growth, but that this enzyme participates in the glyoxylate cycle only when it is incorporated into a particulate structure.

A Re-Appraisal of the Role of Blood Coagulation and Platelets in the Generalized Shwartzman Phenomenon

1966 ◽  
Vol 15 (03/04) ◽  
pp. 519-538 ◽  
Author(s):  
J Levin ◽  
E Beck
Keyword(s):  
Blood Coagulation ◽  
The State ◽  
Coagulation System ◽  
Renal Lesions ◽  
Intravascular Coagulation ◽  
Renal Glomeruli ◽  
Coagulation Mechanism ◽  
Shwartzman Phenomenon ◽  
Do So

SummaryThe role of intravascular coagulation in the production of the generalized Shwartzman phenomenon has been evaluated. The administration of endotoxin to animals prepared with Thorotrast results in activation of the coagulation mechanism with the resultant deposition of fibrinoid material in the renal glomeruli. Anticoagulation prevents alterations in the state of the coagulation system and inhibits development of the renal lesions. Platelets are not primarily involved. Platelet antiserum produces similar lesions in animals prepared with Thorotrast, but appears to do so in a manner which does not significantly involve intravascular coagulation.The production of adrenal cortical hemorrhage, comparable to that seen in the Waterhouse-Friderichsen syndrome, following the administration of endotoxin to animals that had previously received ACTH does not require intravascular coagulation and may not be a manifestation of the generalized Shwartzman phenomenon.

‘Wheels have been set in motion’: Geocentrism and Relativity in Tom Stoppard’s Rosencrantz and Guildenstern Are Dead

2018 ◽  
Author(s):  
Liliane Campos
Keyword(s):  
20Th Century ◽  
Film Adaptation ◽  
Frames Of Reference ◽  
Quantum Uncertainty ◽  
Galilean Relativity ◽  
Modern Physics ◽  
20Th Century Physics ◽  
Time Specific ◽  
Do So

By decentring our reading of Hamlet, Stoppard’s tragicomedy questions the legitimacy of centres and of stable frames of reference. So Liliane Campos examines how Stoppard plays with the physical and cosmological models he finds in Hamlet, particularly those of the wheel and the compass, and gives a new scientific depth to the fear that time is ‘out of joint’. In both his play and his own film adaptation, Stoppard’s rewriting gives a 20th-century twist to these metaphors, through references to relativity, indeterminacy, and the role of the observer. When they refer to the uncontrollable wheels of their fate, his characters no longer describe the destruction of order, but uncertainty about which order is at work, whether heliocentric or geocentric, random or tragic. When they express their loss of bearings, they do so through the thought experiments of modern physics, from Galilean relativity to quantum uncertainty, drawing our attention to shifting frames of reference. Much like Schrödinger’s cat, Stoppard’s Rosencrantz and Guildenstern are both dead and alive. As we observe their predicament, Campos argues, we are placed in the paradoxical position of the observer in 20th-century physics, and constantly reminded that our time-specific relation to the canon inevitably determines our interpretation.

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