scholarly journals Seeking Europa's Ocean

2010 ◽  
Vol 6 (S269) ◽  
pp. 101-114 ◽  
Author(s):  
Robert T. Pappalardo
Keyword(s):  
Salt Water ◽  
Global Ocean ◽  
Icy Satellites ◽  
Induced Magnetic Field ◽  
Ice Surface ◽  
Ring Structures ◽  
Tidally Driven ◽  
Nonsynchronous Rotation ◽  
Spacecraft Data ◽  
Ice Shell

AbstractGalileo spacecraft data suggest that a global ocean exists beneath the frozen ice surface Jupiter's moon Europa. Since the early 1970s, planetary scientists have used theoretical and observational arguments to deliberate the existence of an ocean within Europa and other large icy satellites. Galileo magnetometry data indicates an induced magnetic field at Europa, implying a salt water ocean. A paucity of large craters argues for a surface on average only ~40-90 Myr old. Two multi-ring structures suggest that impacts punched through an ice shell ~20 km thick. Europa's ocean and surface are inherently linked through tidal deformation of the floating ice shell, and tidal flexing and nonsynchronous rotation generate stresses that fracture and deform the surface to create ridges and bands. Dark spots, domes, and chaos terrain are probably related to tidally driven ice convection along with partial melting within the ice shell. Europa's geological activity and probable mantle contact permit the chemical ingredients necessary for life to be present within the satellite's ocean. Astonishing geology and high astrobiological potential make Europa a top priority for future spacecraft exploration, with a primary goal of assessing its habitability.

scholarly journals Modeling climate diversity, tidal dynamics and the fate of volatiles on TRAPPIST-1 planets

2018 ◽  
Vol 612 ◽  
pp. A86 ◽  
Author(s):  
Martin Turbet ◽  
Emeline Bolmont ◽  
Jeremy Leconte ◽  
François Forget ◽  
Franck Selsis ◽  
...  
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Planetary Science ◽  
Water Ice ◽  
Planetary Evolution ◽  
Ice Surface ◽  
Surface Condensation ◽  
Synchronous Rotation ◽  
Ice Shell

TRAPPIST-1 planets are invaluable for the study of comparative planetary science outside our solar system and possibly habitability. Both transit timing variations (TTV) of the planets and the compact, resonant architecture of the system suggest that TRAPPIST-1 planets could be endowed with various volatiles today. First, we derived from N-body simulations possible planetary evolution scenarios, and show that all the planets are likely in synchronous rotation. We then used a versatile 3D global climate model (GCM) to explore the possible climates of cool planets around cool stars, with a focus on the TRAPPIST-1 system. We investigated the conditions required for cool planets to prevent possible volatile species to be lost permanently by surface condensation, irreversible burying or photochemical destruction. We also explored the resilience of the same volatiles (when in condensed phase) to a runaway greenhouse process. We find that background atmospheres made of N2, CO, or O2are rather resistant to atmospheric collapse. However, even if TRAPPIST-1 planets were able to sustain a thick background atmosphere by surviving early X/EUV radiation and stellar wind atmospheric erosion, it is difficult for them to accumulate significant greenhouse gases like CO2, CH4, or NH3. CO2can easily condense on the permanent nightside, forming CO2ice glaciers that would flow toward the substellar region. A complete CO2ice surface cover is theoretically possible on TRAPPIST-1g and h only, but CO2ices should be gravitationally unstable and get buried beneath the water ice shell in geologically short timescales. Given TRAPPIST-1 planets large EUV irradiation (at least ~103 × Titan’s flux), CH4and NH3are photodissociated rapidly and are thus hard to accumulate in the atmosphere. Photochemical hazes could then sedimentate and form a surface layer of tholins that would progressively thicken over the age of the TRAPPIST-1 system. Regarding habitability, we confirm that few bars of CO2would suffice to warm the surface of TRAPPIST-1f and g above the melting point of water. We also show that TRAPPIST-1e is a remarkable candidate for surface habitability. If the planet is today synchronous and abundant in water, then it should very likely sustain surface liquid water at least in the substellar region, whatever the atmosphere considered.

Mechanics of tidally driven fractures in Europa's ice shell

Icarus ◽  
2005 ◽  
Vol 177 (2) ◽  
pp. 367-379 ◽  
Author(s):  
Sunwoong Lee ◽  
Robert T. Pappalardo ◽  
Nicholas C. Makris
Keyword(s):  
Tidally Driven ◽  
Ice Shell

scholarly journals How does salinity shape ocean circulation and ice geometry on Enceladus and other icy satellites?

2021 ◽  
Author(s):  
Wanying Kang ◽  
Tushar Mittal ◽  
Suyash Bire ◽  
Jean Michel ◽  
John Marshall
Keyword(s):  
Ocean Circulation ◽  
Freezing Point ◽  
Ocean Dynamics ◽  
Icy Satellites ◽  
Heating Rates ◽  
Ocean Salinity ◽  
Thickness Variations ◽  
Tidal Heating ◽  
Ice Shell ◽  
Shell Geometry

Abstract Of profound astrobiological interest is that not only does Enceladus have a water ocean, but it also appears to be salty, important for its likely habitability. Here, we investigate how salinity affects ocean dynamics and equilibrium ice shell geometry and use knowledge of ice shell geometry and tidal heating rates to help constrain ocean salinity. We show that the vertical overturning circulation of the ocean, driven from above by melting and freezing and the temperature dependence of the freezing point of water on pressure, has opposing signs at very low and very high salinities. In both cases, heat and freshwater converges toward the equator, where the ice is thick, acting to homogenise thickness variations. In order to maintain observed ice thickness variations, ocean heat transport should not overwhelm tidal heating rates within the ice, which are small in equatorial regions. This can only happen when the ocean’s salinity has intermediate values, order 20 psu. In this case polar-sinking driven by meridional temperature variations is largely canceled by equatorial-sinking circulation driven by salinity variations and a consistent ocean circulation, ice shell geometry and tidal heating rate can be achieved.

scholarly journals Impact of variable sea-water conductivity on motional induction simulated with an OGCM

2015 ◽  
Vol 12 (4) ◽  
pp. 1869-1891 ◽  
Author(s):  
C. Irrgang ◽  
J. Saynisch ◽  
M. Thomas
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Temporal Variability ◽  
Sea Water ◽  
Temporal Variations ◽  
Global Ocean ◽  
Induced Magnetic Field ◽  
Magnetic Signal ◽  
Water Conductivity ◽  
Induction Process

Abstract. Carrying high concentrations of dissolved salt, ocean water is a good electrical conductor. As sea-water flows through the Earth's ambient geomagnetic field, electric fields are generated, which in turn induce secondary magnetic fields. In current models for oceanic induced magnetic fields, a realistic consideration of sea-water conductivity is often neglected and the effect on the variability of the oceanic induced magnetic field unknown. To model magnetic fields that are induced by non-tidal global ocean currents, an electromagnetic induction model is implemented into the Ocean Model for Circulation and Tides (OMCT). This provides the opportunity to not only model oceanic induced magnetic signals, but to assess the impact of oceanographic phenomena on the induction process. In this paper, the sensitivity of the induction process due to spatial and temporal variations in sea-water conductivity is investigated. It is shown that assuming an ocean-wide uniform conductivity is insufficient to accurately capture the temporal variability of the magnetic signal. Using instead a realistic global sea-water conductivity distribution increases the temporal variability of the magnetic field up to 45 %. Especially vertical gradients in sea-water conductivity prove to be a key factor for the variability of the oceanic induced magnetic field. However, temporal variations of sea-water conductivity only marginally affect the magnetic signal.

scholarly journals How does deposition of gas phase species affect pH at frozen salty interfaces?

2012 ◽  
Vol 12 (8) ◽  
pp. 19277-19301
Author(s):  
S. N. Wren ◽  
D. J. Donaldson
Keyword(s):  
Gas Phase ◽  
Chemical Nature ◽  
Salt Water ◽  
Oxidative Capacity ◽  
Spectroscopic Technique ◽  
Surface Deposition ◽  
Ph Changes ◽  
Ph Response ◽  
Ice Surface ◽  
Poor Understanding

Abstract. Chemical processes occurring on snow and ice surfaces play an important role in controlling the oxidative capacity of the overlying atmosphere. However, efforts to gain a better, mechanistic understanding of such processes are impeded by our poor understanding of the chemical nature of the air-ice interface. Here we use a surface-sensitive spectroscopic technique to investigate how the nature of the ice, whether frozen freshwater, salt water or seawater, influences pH changes at the surface. Deposition of HCl(g) leads to a very different pH response at the frozen freshwater surface than at the frozen salt water surface indicating that these two surfaces present different chemical environments. Importantly, the sea ice surface is buffered against pH changes arising from deposition of gas phase species. These results have important implications for understanding pH-sensitive processes occurring at the air-ice boundary, such as bromine activation.

scholarly journals GEOELECTRICAL SECTION OF THE BARGUZIN BAY OF LAKE BAIKAL ACCORDING TO GEORADAR AND RADIO IMPEDANCE SOUNDING DATA

2020 ◽  
Vol 11 (4) ◽  
pp. 806-816
Author(s):  
Yu. B. Bashkuev ◽  
V. B. Khaptanov ◽  
M. G. Dembelov
Keyword(s):  
Electrical Conductivity ◽  
Lake Baikal ◽  
Electrical Resistance ◽  
Water Area ◽  
Earthquake Forecasting ◽  
Bottom Soil ◽  
Electromagnetic Data ◽  
Ice Surface ◽  
Ring Structures ◽  
Physical And Chemical

Electrical resistivity (electrical conductivity) of water and bottom soil of the Barguzin Bay was studied by radio impedance soundings in VLF/LF bands, and the measurements were analysed. The georadar sounding method was used to investigate dielectric permittivity of freshwater ice (dielectric constant is ε=3.4). We developed the technique of radio impedance sounding from the ice surface of Lake Baikal for measuring the electrical resistance of bottom soil in the water area, and applied this technique to a layered model of a medium with a base showing poor/good conductivity. Geoelectric models were constructed for the Barguzin Bay coast and the southern Lake Baikal. The geoelectrical section (GES) of the water area can be useful for earthquake forecasting from electromagnetic data, as well as for analysing the physical and chemical causes of the occurrence of ring structures on the ice surface of Lake Baikal.

Reply to “Comment on ‘Mechanics of tidally driven fractures in Europa's ice shell’ ”

Icarus ◽  
2007 ◽  
Vol 189 (2) ◽  
pp. 598-599 ◽  
Author(s):  
S LEE ◽  
R PAPPALARDO ◽  
N MAKRIS
Keyword(s):  
Tidally Driven ◽  
Ice Shell

Sill Processes in the Saguenay Fjord

2020 ◽  
Author(s):  
Jérôme Guay ◽  
Daniel Bourgault ◽  
Cynthia Bluteau ◽  
Cédric Chavanne ◽  
Peter Galbraith ◽  
...  
Keyword(s):  
Hydraulic Jump ◽  
Large Scale ◽  
Salt Water ◽  
Tidal Flow ◽  
Late Winter ◽  
Lawrence Estuary ◽  
Saguenay Fjord ◽  
Subsurface Waters ◽  
Tidally Driven ◽  
Saguenay River

<p>The Saguenay Fjord is a 110 km long and 250 m deep (max depth) multi-silled glacial valley that connects the Saguenay River at its head with the St. Lawrence Estuary at its mouth. The bathymetry is characterized with 3 sills: a shallow 20-m deep sill at the mouth, an intermediate 60-m deep 20 km landward sill and a deep 120-m sill 35 km landward. These sills separate 3 basins, the outer, the intermediate and the inner basins. The circulation in the fjord is forced by the Saguenay River at its head that brings freshwater, large tides (up to 6 m range) at its mouth that brings salt water and by wind. The large-scale circulation has been characterized by three seasonally dependent regimes during which the deep, intermediate and subsurface waters of the inner basin are being renewed, respectively, during early winter, summer and late winter. There are indirect indications that those regimes are determined by turbulent processes occurring locally at each of these three sills. Here, we carried out a field experiment to more directly investigate the detailed dynamics of tidally-driven sill processes and water mass modifications occurring across these three sills. Our measurements provide to date the most accurate and complete description of the stratified tidal flow structures around these sills. We also found that an internal hydraulic jump seems to form every ebb tide on the seaward side of the intermediate sill but not during flood tide on the landward side. Research is ongoing to better understand this asymmetry but our hypothesis is that it is the presence of a salty pool landward of the sill that prevents the formation of a hydraulic jump, a process that may be similar to that documented in Knight Inlet (British Columbia, Canada).</p>

Sign in / Sign up

Export Citation Format

Share Document