The role of proton precipitation in Jovian aurora: Theory and observation

It was proposed that the Jovian auroral emissions observed by Voyager spacecraft could be explained by energetic protons precipitating into the upper atmosphere of Jupiter. Such precipitation of energetic protons results in Doppler-shifted Lyman alpha emission that can be quantitatively analyzed to determine the energy flux and energy distribution of the incoming particle beam. Modeling of the expected emission from a reasonably chosen Voyager energetic proton spectrum can be used in conjunction with International Ultraviolet Explorer (IUE) observations, which show a relative lack of red-shifted Lyman alpha emission, to set upper limits on the amount of proton precipitation taking place in the Jovian aurora. Such calculations indicate that less than 10 percent of the ultraviolet auroral emissions at Jupiter can be explained by proton precipitation

Superthermal electron processes in the upper atmosphere of Uranus: Aurora and electroglow

Strong ultraviolet emissions from the upper atmosphere of Uranus suggest that both auroral and electroglow phenomena are of significant aeronomical consequences in the structure of the upper atmosphere. Combined modeling and data analysis were performed to determine the effect of electroglow and auroral phenomena on the global heat and atomic hydrogen budgets in the Uranus upper atmosphere. The results indicate that the auroral and electroglow heat sources are not adequate to explain the high exospheric temperature observed at Uranus, but that the atomic hydrogen supplied by these processes is more than sufficient to explain the observations. The various superthermal electron distributions modeled have significantly different efficiencies for the various processes such as UV emission, heating, ionization, and atomic hydrogen production, and produce quite different H2 band spectra. However, additional information on the UV spectra and global parameters is needed before modeling can be used to distinguish between the possible mechanisms for electroglow

Note and Comment

Sales - Liability for the Presence of Mice and Other Uncommon Things in Food - A group of recent decisions presents a somewhat farcical conformity with Montesquiet\u27. thesis that law may vary with time and geography. It strikingly illustrates, also, the importance of the particular theory of liability upon which a suit is predicated. The unusual similarity in detail of the operative facts of these cases lends peculiar emphasis to the difference in the judgments rendered

Book Reviews

A collection of book reviews by multiple authors

A protosolar nebula origin for the ices agglomerated by Comet 67P/Churyumov-Gerasimenko

The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the protosolar nebula. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the protosolar nebula. On the basis of existing laboratory and modeling data, we find that the N$_2$/CO and Ar/CO ratios measured in the coma of the Jupiter family comet 67P/Churyumov-Gerasimenko by the ROSINA instrument aboard the European Space Agency's Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N$_2$/CO and Ar/CO ratios in 67P/Churyumov-Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov-Gerasimenko is impoverished in Ar and N$_2$, the volatile enrichments observed in Jupiter's atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation.Comment: The Astrophysical Journal Letters, in pres

Note and Comment

Repeals by Implication - Prohibition in Michigan - At the November election of. 1916 the people of the state of Michigan ratified the following amendment to the constitution of that state: The manufacture, sale, giving away, bartering or furnishing of any vinous, malt, brewed, fermented, spiritous or intoxicating liquors, except for medicinal, mechanical, chemical, scientific or sacramental purposes shall be after April thirty, nineteen hundred eighteen, prohibited in the State forever. The Legislature shall by law provide regulations for the sale of such liquors for medicinal, mechanica, cheinical, scientific and sacramental purposes

Titan Mare Explorer (TiME): first in situ exploration of an extraterrestrial sea

The lakes and seas of Titan are a sink of products of photolysis in the atmosphere, and a crucial component in Titan's active methane cycle. In situ exploration of the seas is necessary to understand their intriguing prebiotic organic chemistry

Scientific rationale of a Saturn probe mission

We describe the main scientific goals to be addressed by future in situ exploration of Saturn