Physical State of the Deep Interior of the CoRoT-7b Exoplanet

The present study takes the CoRoT-7b exoplanet as an analogue for massive terrestrial planets to investigate conditions, under which intrinsic magnetic fields could be sustained in liquid cores. We examine the effect of depth-dependent transport parameters (e.g., activation volume of mantle rock) on a planet's thermal structure and the related heat flux across the core mantle boundary. For terrestrial planets more massive than the Earth, our calculations suggest that a substantial part of the lowermost mantle is in a sluggish convective regime, primarily due to pressure effects on viscosity. Hence, we find substantially higher core temperatures than previously reported from parameterized convection models. We also discuss the effect of melting point depression in the presence of impurities (e.g., sulfur) in iron-rich cores and compare corresponding melting relations to the calculated thermal structure. Since impurity effects become less important at the elevated pressure and temperature conditions prevalent in the deep interior of CoRoT-7b, iron-rich cores are likely solid, implying that a self-sustained magnetic field would be absent.Comment: 4 pages, 3 figures. IAU 276 Proceeding

Nitrate and nitrite variability at the seafloor of an oxygen minimum zone revealed by a novel microfluidic in-situ chemical sensor

Microfluidics, or lab-on-a-chip (LOC) is a promising technology that allows the development of miniaturized chemical sensors. In contrast to the surging interest in biomedical sciences, the utilization of LOC sensors in aquatic sciences is still in infancy but a wider use of such sensors could mitigate the undersampling problem of ocean biogeochemical processes. Here we describe the first underwater test of a novel LOC sensor to obtain in situ calibrated time-series (up to 40 h) of nitrate+nitrite (ΣNOx) and nitrite on the seafloor of the Mauritanian oxygen minimum zone, offshore Western Africa. Initial tests showed that the sensor successfully reproduced water column (160 m) nutrient profiles. Lander deployments at 50, 100 and 170 m depth indicated that the biogeochemical variability was high over the Mauritanian shelf: The 50 m site had the lowest ΣNOx concentration, with 15.2 to 23.4 μM (median=18.3 μM); while at the 100 site ΣNOx varied between 21.0 and 30.1 μM over 40 hours (median = 25.1μM). The 170 m site had the highest median ΣNOx level (25.8 μM) with less variability (22.8 to 27.7 μM). At the 50 m site, nitrite concentration decreased fivefold from 1 to 0.2 μM in just 30 hours accompanied by decreasing oxygen and increasing nitrate concentrations. Taken together with the time series of oxygen, temperature, pressure and current velocities, we propose that the episodic intrusion of deeper waters via cross-shelf transport leads to intrusion of nitrate-rich, but oxygen-poor waters to shallower locations, with consequences for benthic nitrogen cycling. This first validation of an LOC sensor at elevated water depths revealed that when deployed for longer periods and as a part of a sensor network, LOC technology has the potential to contribute to the understanding of the benthic biogeochemical dynamics

Odyssey 2 : A mission toward Neptune and Triton to test General Relativity

Odyssey 2 will be proposed in December 2010 for the next call of M3 missions for Cosmic Vision 2015-2025. This mission, under a Phase 0 study performed by CNES, will aim at Neptune and Triton. Two sets of objectives will be pursued. The first one is to perform a set of gravitation experiments at the Solar System scale. Experimental tests of gravitation have always shown good agreement with General Relativity. There are however drivers to continue testing General Relativity, and to do so at the largest possible scales. From a theoretical point of view, Einstein's theory of gravitation shows inconsistencies with a quantum description of Nature and unified theories predict deviations from General Relativity. From an observational point of view, as long as dark matter and dark energy are not observed through other means than their gravitational effects, they can be considered as a manifestation of a modification of General Relativity at cosmic scales. The scientific objectives are to: (i) test the gravitation law at the Solar System scale; (ii) measure the Eddington parameter; and (iii) investigate the navigation anomalies during fly-bys. To fulfil these objectives, the following components are to be on board the spacecraft: (i) the Gravity Advanced Package (GAP), which is an electrostatic accelerometer to which a rotating stage is added; (ii) radio-science; (iii) laser ranging, to improve significantly the measure of the Eddington parameter. The second set of objectives is to enhance our knowledge of Neptune and Triton. Several instruments dedicated to planetology are foreseen: camera, spectrometer, dust and particle detectors, and magnetometer. Depending on the ones kept, the mission could provide information on the gravity field, the atmosphere and the magnetosphere of the two bodies as well as on the surface geology of Triton and on the nature of the planetary rings around Neptune.Comment: 61st International Astronautical Congress (Prague, Czech Republic - September 2010), 7 page

Effect of mantle oxidation state and escape upon the evolution of Earth's magma ocean atmosphere

The magma ocean period was a critical phase determining how Earth atmosphere developed into habitability. However there are major uncertainties in the role of key processes such as outgassing from the planetary interior and escape of species to space that play a major role in determining the atmosphere of early Earth. We investigate the influence of outgassing of various species and escape of H$_2$ for different mantle redox states upon the composition and evolution of the atmosphere for the magma ocean period. We include an important new atmosphere-interior coupling mechanism namely the redox evolution of the mantle which strongly affects the outgassing of species. We simulate the volatile outgassing and chemical speciation at the surface for various redox states of the mantle by employing a C-H-O based chemical speciation model combined with an interior outgassing model. We then apply a line-by-line radiative transfer model to study the remote appearance of the planet in terms of the infrared emission and transmission. Finally, we use a parameterized diffusion-limited and XUV energy-driven atmospheric escape model to calculate the loss of H$_2$ to space. We have simulated the thermal emission and transmission spectra for reduced or oxidized atmospheres present during the magma ocean period of Earth. Reduced or thin atmospheres consisting of H$_2$ in abundance emit more radiation to space and have larger effective height as compared to oxidized or thick atmospheres which are abundant in H$_2$O and CO$_2$. We obtain the outgassing rates of H2 from the mantle into the atmosphere to be a factor of ten times larger than the rates of diffusion-limited escape to space. Our work presents useful insight into the development of Earth atmosphere during the magma ocean period as well as input to guide future studies discussing exoplanetary interior compositions.Comment: 26 pages, 15 figures, accepted for publicatio

The role of Cx36 and Cx43 in 4‐aminopyridine‐induced rhythmic activity in the spinal nociceptive dorsal horn: an electrophysiological study in vitro

Connexin (Cx) proteins and gap junctions support the formation of neuronal and glial syncytia that are linked to different forms of rhythmic firing and oscillatory activity in the CNS. In this study, quantitative reverse transcription polymerase chain reaction (RT‐qPCR) was used to profile developmental expression of two specific Cx proteins, namely glial Cx43 and neuronal Cx36, in postnatal lumbar spinal cord aged 4, 7, and 14 days. Extracellular electrophysiology was used to determine the contribution of Cx36 and Cx43 to a previously described form of 4‐aminopyridine (4‐AP)‐induced 4–12 Hz rhythmic activity within substantia gelatinosa (SG) of rat neonatal dorsal horn (DH) in vitro. The involvement of Cx36 and Cx43 was probed pharmacologically using quinine, a specific uncoupler of Cx36 and the mimetic peptide blocker Gap 26 which targets Cx43. After establishment of 4–12 Hz rhythmic activity by 4‐AP (25 μmol/L), coapplication of quinine (250 μmol/L) reduced 4‐AP‐induced 4–12 Hz rhythmic activity (P < 0.05). Preincubation of spinal cord slices with Gap 26 (100 μmol/L), compromised the level of 4‐AP‐induced 4–12 Hz rhythmic activity in comparison with control slices preincubated in ACSF alone (P < 0.05). Conversely, the nonselective gap junction “opener” trimethylamine (TMA) enhanced 4–12 Hz rhythmic behavior (P < 0.05), further supporting a role for Cx proteins and gap junctions. These data have defined a physiological role for Cx36 and Cx43 in rhythmic firing in SG, a key nociceptive processing area of DH. The significance of these data in the context of pain and Cx proteins as a future analgesic drug target requires further study

Candidate regions on titan as promising landing sites for future in situ missions

The highly successful and still on-going Cassini-Huygens mission to the Saturnian system points to the need for a return mission, with both remote and in situ instrumentation. The surface of Saturn’s moon Titan, hosts a complex environment in which many processes occur shaping its landscape. Several of its geological features resemble terrestrial ones, albeit constructed from different material and reflecting the interiorsurface-atmosphere exchanges. The resulting observed morphotectonic features and cryovolcanic candidate regions could benefit from further extensive exploration by a return mission that would focus on these aspects with adapted state-of-the-art instrumentation affording higher spectral and spatial resolution and in situ capabilities. We suggest that some features on Titan are more promising candidate locations for future landing and we present the case for Tui Regio, Hotei Regio and Sotra Patera as to why they could provide a wealth of new scientific results

Spectral investigation of volcanic alteration deposits on Vulcano island /Italy as planetary analog for acid alteration conditions on Mars

During the fifth International Summer School held on Vulcano (Eolian Islands, Italy) in June 2019 we started the investigation of volcanic deposits with different spectral instruments combining mineralogical, elemental and molecular information [1, 2]. The island of Vulcano presents an extremely large variety of volcanic products [3] in extreme acid alteration conditions. Acidic alteration may also have been a key process throughout Martian geologic history making Vulcano a perfect analog for studies on Mars by defining the geochemistry at these sites. In this work we present an update of our spectral investigations based on the VIS-NIR spectral measurements

Modeling magnetospheric fields in the Jupiter system

The various processes which generate magnetic fields within the Jupiter system are exemplary for a large class of similar processes occurring at other planets in the solar system, but also around extrasolar planets. Jupiter's large internal dynamo magnetic field generates a gigantic magnetosphere, which is strongly rotational driven and possesses large plasma sources located deeply within the magnetosphere. The combination of the latter two effects is the primary reason for Jupiter's main auroral ovals. Jupiter's moon Ganymede is the only known moon with an intrinsic dynamo magnetic field, which generates a mini-magnetosphere located within Jupiter's larger magnetosphere including two auroral ovals. Ganymede's magnetosphere is qualitatively different compared to the one from Jupiter. It possesses no bow shock but develops Alfv\'en wings similar to most of the extrasolar planets which orbit their host stars within 0.1 AU. New numerical models of Jupiter's and Ganymede's magnetospheres presented here provide quantitative insight into the processes that maintain these magnetospheres. Jupiter's magnetospheric field is approximately time-periodic at the locations of Jupiter's moons and induces secondary magnetic fields in electrically conductive layers such as subsurface oceans. In the case of Ganymede, these secondary magnetic fields influence the oscillation of the location of its auroral ovals. Based on dedicated Hubble Space Telescope observations, an analysis of the amplitudes of the auroral oscillations provides evidence that Ganymede harbors a subsurface ocean. Callisto in contrast does not possess a mini-magnetosphere, but still shows a perturbed magnetic field environment. Callisto's ionosphere and atmospheric UV emission is different compared to the other Galilean satellites as it is primarily been generated by solar photons compared to magnetospheric electrons.Comment: Chapter for Book: Planetary Magnetis