Miocene sponge assemblages in the face of the Messinian Salinity Crisis—new data from the Atlanto-Mediterranean seaway

The Messinian Salinity Crisis is considered as one of the most influential Cenozoic events that impacted negatively on the benthic fauna of the Mediterranean area. Changing environmental conditions, including a sharp reduction of water exchange between the Mediterranean Sea and the Atlantic Ocean, altered the geographical ranges of many organisms, including sponges (Porifera). Here, we report a unique assemblage of isolated sponge spicules from the upper Miocene of southwestern Spain. The newly recognized sponge fauna was inhabiting the Guadalquivir Basin—the corridor between the Mediterranean and the Atlantic Ocean at that time. It represents a taxonomically rich sponge community that consisted of members of “soft” and “lithistid” demosponges and hexactinellids. Demosponges are represented by at least thirty-four taxa, while hexactinellids are significantly rarer; only six taxa have been identified. From among eighteen taxa recognized to the species level, at least eight seem to be inhabiting this area to these days; six are recorded from adjacent areas, such as the Western Mediterranean, South European Atlantic Shelf, and the Azores, and three are present in the Red Sea and/or the Northern Atlantic. Intriguingly, some taxa seem to have their closest relatives in distant areas, such as the Indo-Pacific and Japanese waters which suggests that the range of some once widely-distributed populations shrunk after the isolation of the Mediterranean and the Messinian Salinity Crisis, surviving to the present day only in refugia.This work was supported by EVAMED (PID2020-118999GB-I00) funded by the Spanish Ministry of Science and Innovation/State Research Agency of Spain (AEI)

Trade-off analysis of C12A7: e-deposition techniques applied to Low Work Function Tethers

Due to its extraordinary properties, the C12A7:e− electride has been suggested in the past as one of the most promising materials for coating Low Work-function Tethers (LWTs). Such subclass of electrodynamic tether, made of a conductive substrate coated with materials that enhance the electron emission through the thermionic and photoelectric effects, would constitute a fully passive and consumable-free device for deorbiting space debris from Low Earth Orbit. This work presents experimental results on the manufacturing and testing of small tape-like LWT samples, which is the relevant geometry for electrodynamic tether applications. After preparing C12A7:e− targets under specific and controlled conditions, thin titanium foils have been coated with the C12A7:e− electride by using two different physical vapor deposition techniques: magnetron sputtering (MS) and pulsed laser deposition (PLD). In the case of MS, important difficulties and defects were found, including target damage, poor growth rate, and oxidation and changes in the composition of the coating. However, the performance on the PLD coating was radically different. First, Rutherford backscattering spectrometry confirmed that the composition of the thin film with the PLD coincides with that of the target. Second, X-ray photoelectron spectroscopy and thermionic emission experiments showed that the work function of the LWT sample is 2.6 ± 0.1 eV. Therefore, the trade-off analysis indicates that PLD can be used to manufacture LWT samples with work function close to the one of the bulk C12A7:e− (2.4 eV). Nevertheless, its application as passive cathode in electrodynamic tethers still requires further research activities.This work was supported by Agencia Estatal de Investigación (Ministerio de Ciencia, Innovación y Universidades of Spain) under the project ESP2017-82092-ERC (AEI). Work by JFP and AP has been supported by the Centro para el Desarrollo Tecnológico e Industrial (CDTI) under the project IDI-20171255. FJP and PT acknowledge the support by ATD under project contract ICMM-CSIC #010101170104. SN work is supported by Comunidad de Madrid (Spain) under the Grant 2018/T2IND/11352. GSA work is supported by the Ministerio de Ciencia, Innovación y Universidades of Spain under the Grant RYC-2014-15357