Mount Etna as a terrestrial laboratory to investigate recent volcanic activity on Venus by future missions:A comparison with Idunn Mons, Venus

The recently selected missions to Venus have opened a new era for the exploration of this planet. These missions will provide information about the chemistry of the atmosphere, the geomorphology, local-to-regional surface composition, and the rheology of the interior. One key scientific question to be addressed by these future missions is whether Venus remains volcanically active, and if so, how its volcanism is currently evolving. Hence, it is fundamental to analyze appropriate terrestrial analog sites for the study of possibly active volcanism on Venus. To this regard, we propose Mount Etna - one of the most active and monitored volcanoes on Earth - as a suitable terrestrial laboratory for remote and in-situ investigations to be performed by future missions to Venus. Being characterized by both effusive and explosive volcanic products, Mount Etna offers the opportunity to analyze multiple eruptive styles, both monitoring active volcanism and identifying the possible occurrence of pyroclastic activity on Venus. We directly compare Mount Etna with Idunn Mons, one of the most promising potentially active volcanoes of Venus. Despite the two structures show a different topography, they also show some interesting points of comparison, and in particular: a) comparable morpho-structural setting, since both volcanoes interact with a rift zone, and b) morphologically similar volcanic fields around both Mount Etna and Idunn Mons. Given its ease of access, we also propose Mount Etna as an analog site for laboratory spectroscopic studies to identify the signatures of unaltered volcanic deposits on Venus

6th international symposium on earthworm ecology

This study compares the origin and activities of glycolytic enzymes present in the gut contents of some geophagous adult earthworms and demonstrates that all the species did not develop mutualistic relationships with the ingested microorganisms to digest soil organic matter. Although the glycolytic activities were rather weak in the earthworms studied, they possess quite a complete enzymatic system that allows to degrade root and fungal substrates available in soils. #Millsonia anomala Omo. from Lamto (Côte d'Ivoire) and #Hormogaster elisae Alvarez from El Molar (Madrid) developed a strong mutualistic earthworm-microflora digestion system for hydrolysing cellulose : cellulase produced by inested microflora is able to degrade cellulose to cellobiose, cellobiase released by the worm itself breaks down cellobiose into D-glucose. Both enzymes found in intestinal contents of #Pontoscolex corethrurus Müll. from Palma Sola, Veracruz (Mexico) were produced by ingested soil microflora since they were not found in gut tissue culture. On the contrary, #Polypheretima elongata Perr. from Sainte Anne (Martinique), #Hyperiodrilus africanus Bedd. and #Dichogaster terrae nigrae Omo. et Vld. from Lamto (Cîte d'Ivoire) possess a complete enzymatic system for hydrolyzing cellulose. They could synthesize cellulolytic enzymes, i.e. cellulase and cellobiase by themselves. In the course of their digestion, geophagous earthworms seem to display variable adaptive characters which are undoubtedly linked to the different ecological categories and niches. (Résumé d'auteur

6th international symposium on earthworm ecology

The gut mucus production of different earthworms species has been measured in order to verify the mutualistic hypothesis between earthworms and soil microflora. Earthworms of different origin (tropical and temperate) and ecological category (endogeic, anecic and epigeic), individuals of the same species occupying different soils, and earthworms of different species from the same soil, have been studied. Intestinal mucus production suggests the existence of the mutualistic digestion system. The mucus percentage in the gut was greater in the epigeic than in both anecic and endogeic. Nevertheless, the relative enrichment was higher in the endogeic species. The organic matter content of the substratum seems to play a regulating role in the mutualistic system, because the greater the substratum organic matter content the lower the relative enrichment. Generally, in temperate zones more mucus was added to the substratum, suggesting that the low temperature do necessary a greater microflora simulation. (Résumé d'auteur

Coral reef annihilation, persistence and recovery at Earth's youngest volcanic island

The structure and function of coral reef ecosystems is increasingly compromised by multiple stressors, even in the most remote locations. Severe, acute disturbances such as volcanic eruptions represent extreme events that can annihilate entire reef ecosystems, but also provide unique opportunities to examine ecosystem resilience and recovery. Here, we examine the destruction, persistence and initial recovery of reefs associated with the hydro-magmatic eruption that created Earth's newest landmass, the Hunga Tonga-Hunga Ha'apai volcanic island. Despite extreme conditions associated with the eruption, impacts on nearby reefs were spatially variable. Importantly, even heavily affected reefs showed signs of rapid recovery driven by high recruitment, likely from local refuges. The remote location and corresponding lack of additional stressors likely contribute to the resilience of Hunga's reefs, suggesting that in the absence of chronic anthropogenic stressors, coral reefs can be resilient to one of the largest physical disturbances on Earth

6th international symposium on earthworm ecology

The effects of a deep-burrowing earthworm species, #Martiodrilus carimagnuensis, on soil fertility and plant growth were assessed in two grasslands in the Eastern Plains of Colombia. This species aestivates deep in the soil during the dry season. Fibre glass netting was used to prevent colonisation of the top soil at the onset of the humid season. Effects of earthworm absence on soil properties and plant biomass were analysed with principal component analysis. Experimental manipulation succeeded in preventing #M. carimaguensis activity in the top soil. The larger part of the variance in our data (29.35%) was explained by the effect of pasture type and age on soil structure and organic matter. A lesser part (10.81%) was due to the effect of legumes on soil physical properties. The effect of earthworm absence on soil properties and plant growth explained 16.50% of the total variance. #M. carimaguensis$ biomass was associated with low soil compaction, high C contents, low Al saturation, high herbaceous biomass and low weed biomass. These results support the general knowledge of how earthworms can affect soil fertility and plant growth. (Résumé d'auteur

6th international symposium on earthworm ecology

Some data on the reproductive biology of three native glossoscolecid species from the Colombian "Llanos" are presented. The seasonal dynamics of reporduction varied among the species considered which displayed either one or two reproductive periods per year. Cocoons were laid at different depths to a maximum of 50 cm. The relation between cocoon weight and adult weight was the same for two endogeic species, ca. 6%, whereas for one anecic species the value has been the highest obtained to date for any tropical and temperate earthworm, i.e. 16%. (Résumé d'auteur

6th international symposium on earthworm ecology

From April to September 1994, micofauna density, total biomass, and species diversity of earthworms were measured across a range of land use types in the Cabuyal River watershed. The methodology recommended by the Tropical Soil Biology and Fertility Program (TSBF) was used. Macrofauna density, biomass, and diversity of earthworm species varied considerably across land use types, and depths. Principal component analysis yielded three factors that accounted for 71.8% of the total variance in macrofauna density. High taxonomic units values occur in the Andean forest (98 observed), decreasing dramatically in pastures (ranging from 28 to 13) and farm lands (ranging from 31 to 18). (Résumé d'auteur