Volcanically emitted sodium chloride as a source for Io's neutral clouds and plasma torus.

The atmosphere of Jupiter's satellite Io is extremely tenuous, time variable and spatially heterogeneous. Only a few molecules--SO2, SO and S2--have previously been identified as constituents of this atmosphere, and possible sources include frost sublimation, surface sputtering and active volcanism. Io has been known for almost 30 years to be surrounded by a cloud of Na, which requires an as yet unidentified atmospheric source of sodium. Sodium chloride has been recently proposed as an important atmospheric constituent, based on the detection of chlorine in Io's plasma torus and models of Io's volcanic gases. Here we report the detection of NaCl in Io's atmosphere; it constitutes only approximately 0.3% when averaged over the entire disk, but is probably restricted to smaller regions than SO2 because of its rapid photolysis and surface condensation. Although the inferred abundance of NaCl in volcanic gases is lower than predicted, those volcanic emissions provide an important source of Na and Cl in Io's neutral clouds and plasma torus.

Evolution of the outgassing of comet Hale-Bopp (C/1995 O1) from radio observations.

Spectra obtained from ground-based radio telescopes show the progressive release of CO, CH3OH, HCN, H2O (from OH), H2S, CS, H2CO, CH3CN, and HNC as comet Hale-Bopp (C/1995 01) approached the sun from 6.9 to 1.4 astronomical units (AU). The more volatile species were relatively more abundant in the coma far from the sun, but there was no direct correlation between overabundance and volatility. Evidence for H2O sublimation from icy grains was seen beyond 3.5 AU from the sun. The change from a CO-driven coma to an H2O-driven coma occurred at about 3 AU. The gas outflow velocity and temperature increased as Hale-Bopp approached the sun.

Substantial outgassing of CO from comet Hale-Bopp at large heliocentric distance.

When comet C/1995 O1 (Hale-Boop) was discovered, at a distance of seven astronomical units from the sun, it was more than one hundred times brighter than comet Halley at the same distance. A comet's brightness is derived from the reflection of sunlight from dust grains driven away from the nucleus by the sublimation of volatile ices. Near the sun, sublimation of water ice (a main constituent of comet nuclei) is the source of cometary activity; but at its current heliocentric distance, Hale-Boop is too cold for this process to operate. Other comets have shown activity at large distances, and in the case of comet Schwassmann-Wachmann 1, carbon monoxide has been detected in quantities sufficient to generate its observed coma. Here we report the detection of CO emission from Hale-Boop, at levels indicating a very large rate of outgassing. Several other volatile species were searched for, but not detected. Sublimation of CO therefore appears to be responsible for the present activity of this comet, and we anticipate that future observations will reveal the onset of sublimation of other volatile species as the comet continues its present journey towards the sun.

Chemical and thermal response of Jupiter's atmosphere following the impact of comet Shoemaker-Levy 9.

In July 1994, the collisions of the fragments of comet Shoemaker-Levy 9 with Jupiter resulted in dramatic changes in the planet's atmosphere. Observations of the events suggest that the composition and thermal properties of the atmosphere were considerably modified at the impact sites, with the changes persisting for times lasting from minutes to weeks (see, for example, refs 1-4). Here we report observations of the impact sites at millimetre wave-lengths, which reveal strong emission lines associated with carbon monoxide, carbonyl sulphide and carbon monosulphide. The abundance of carbon monoxide in the jovian atmosphere is normally very low; carbonyl sulphide and carbon monosulphide, on the other hand, have not hitherto been detected. We find that the largest fragments (G and K) each produced approximately 10(14) g of carbon monoxide, 3 x 10(12) g of carbonyl sulphide and 3 x 10(11) g of carbon monosulphide, most probably by shock-induced chemical reactions. Our observations also place firm constraints on the thermal response of Jupiter's stratosphere to the impacts.

The polymerase-associated protein (M1) and the matrix protein (M2) from a virulent and an avirulent strain of viral hemorrhagic septicemia virus (VHSV), a fish rhabdovirus.

We have cloned and sequenced the M1 and M2 genes of both a European (virulent) and a North American (avirulent) strains of viral hemorrhagic septicemia virus, an important fish pathogen. We also compared the transcription of the two genes following infection of cells and determined the phosphorylation status and detergent solubility of the two proteins. Despite a total lack of homology with any available rhabdoviral sequence, the two VHSV proteins share comparable structural features with their respective VSV and RV equivalents. Thus, they are likely to exert similar functions. The amino acid sequence of both proteins is highly conserved between the European and the North American strains, indicating a probable common origin. The most remarkable features are that the virulent and avirulent strains differ in the location of the transcription start signal for the M2 gene and in TX-114 detergent solubility of the M2 protein. However, these differences are not paralleled with any observable change at the levels of M2 gene transcription, M2 protein expression, or virion maturation. Thus, they are unlikely to play a significant role in determination of the virulent status.