Description: The solubility of CO 2 in water at different temperature and pressure conditions has been studied for more than 150 years because of the common presence of this system in the Earth, and its importance for engineering and in several biological and geological processes. However, there are many contradictions in the literature with regard to the solubility of CO 2 in salt-rich aqueous solutions, and associated effects such as the salting out have been studied in detail for only few salts such as NaCl or Na 2 SO 4 . In this study we introduce Raman spectroscopy as a useful tool to measure gas solubility in brines. We have obtained the solubility of CO 2 in aqueous solution of MgSO 4 at different concentrations (5 and 17 wt %), in the range of temperatures from 5 to 20 °C and pressures up to 50 bar. The results allow one to approach different aqueous reactions and processes that are relevant in geochemical phenomena of some planetary objects. Thus, we have modelled the degassing processes that could occur through the crust of Europa, a satellite of Jupiter.

Description: Progressive hydrothermal alteration and mineral precipitation can modify the physical properties and mechanical behavior of the affected rocks, increasing the probabilities of phreatic or hydrothermal explosive eruptions. In this work we focus on the study of rock alteration and hydrothermal system of Deception Island, which is one of the most active volcanoes in Antarctica. A characterization of the pre-caldera and syn-caldera rock alterations has been done as a starting point for the understanding of the past and present hydrothermal system in the island. The alteration processes that have affected pre-caldera deposits are related to low temperature (〈200 oC) fluids, with pervasive palagonitisation and precipitation of smectite and zeolite. In some samples carbonate has also been detected. This alteration is consistent with rocks located at the first 500-600 meters depth of the pre-caldera shield volcano, in which the upper part of the sequence was affected by low-temperature acidic hydrothermal fluids that would have caused the dissolution of some phenocrysts and the consequent precipitation of magnesite. An extended palagonitisation characterize the syn-caldera deposits, but smectite and zeolite have also been identified. This is consistent with syn-depositional and meteoric alteration. Therefore, in the studied samples there is no evidence of persistent hydrothermal alteration that could be related to the current hydrothermal system. This work is part of the CSIC Interdisciplinary Thematic Platform (PTI) Polar zone Observatory (PTI-POLARCSIC) activities. This research was partially funded by the MINECO VOLCLIMA (CGL2015-72629-EXP) and HYDROCAL (PID2020-114876GB-I00) MCIN/AEI/10.13039/501100011033 research projects. This research is also supported by the PREDOCS-UB grant.