SR05 Water Flashcards
Water
Iceline
Distance from a central protostar at which volatile species condense into ice grains
* Every volatile species has its own snow line
* The actual temperature and distance depend on the physical model and the solar nebula model
* Formation snow line of H2O (opaque solar nebula and less energetic Sun): 2.7 AU (~170 K)
* Current snow line of H2O: 5 AU
* The inner asteroid belt is largely devoid of water, while the outer asteroids are icy C-class objects
But:
* Ice that was buried beneath dust/regolith during formation can still exist stable in the inner solar system
* Since accretion, impacts of water-rich asteroids and comets have been delivering water to objects
throughout the solar system
* Around 30% of impacting water can be captured by target objects (impact melts, projectile survivors)
* Earth might have received its water through such impacts
Water in the Solar System
Mercury: Ice in PSRs
Venus: Atmospheric water
Earth‘s Moon: Ice in PSRs, subsurface deposits at the poles
Mars: Ice caps, underground ice deposits, atmospheric water
Asteroid Belt: Underground ice deposits (Ceres)
Jupiter: Atmospheric water
* Moons: Surface ice and (salty) liquid subsurface ocean
Saturn: Atmospheric water, rings of water ice
* Moons: Surface ice, salty subsurface ocean of liquid water and an icy mantle
Uranus: Icy mantle
* Moons: Surface water ice and carbon dioxide ice, perhaps liquid water and water ice interiour
Neptune: Icy mantle
* Triton: Mostly water ice crust, perhaps liquid or slushy subsurface ocean
KBOs: Icy dwarf planets and comets
How can we detect and identify water remotely? (on the moon)
Reflectance spectroscopy
Water sublimation residence time time of a water molecule idk how to interpret the graphs in the lecture slides
Origin of lunar water
- Delivery by comets and asteroids
- Solar wind implantation (H reacts with oxygen-bearing minerals)
- Outgassing from the interior
Water accumulated in the topmost KREEP layer during formation, travelling upwards while creating ice
layers depending on temperature and pressure
Lunar water cycle
- Impacts lead to loss or burial
- Dessicated layer in topmost subsurface
- LEND found 4% WEH in Cabeus (surficial)
- LCROSS found 5.6 ± 2.9% in Cabeus (depth)
- More water at greater depth?
Magnitudes of sources
- Comets and asteroids dominate over
solar wind - Total quantity might be 100–1000 Mton
at each pole
Forms of lunar water
Adsorbed, trapped, deposited
Implications for mining
Abundance? –> Uncertainties, resource potential
Accessibility? –> Location of feedstock/mining operations (single site / distributed)
Extractability? –> Beneficiation, separation, energy requirement
Water in the exosphere
Exosphere
* Approx. 1e-11…1e-10 mbar
* 80,000 atoms/cm3
* Dependence on temperatures/illumination
Loss processes:
* Chemical sputtering H ⟶
* Desorption H ⟶
* Photo dissociation ⟶ H
Conversions between H/H2/OH/H2O
Water on Mars
- Korolev crater (2200 km3 of water ice)
- impact craters filled with ice - Polar caps
Layers:
* Seasonal ice cap: CO2 ice forms each Martian autumn-winter and disappears in spring-summer
* Residual ice cap: H2O ice remains stable in size for hundreds of years at least
* Polar layered deposits: thousands of thin layers of H2O ice mixed with dust that fell out of the atmosphere
* Basal unit (north) / Dorsa Argentea Formation (south): sand and dust mixed with H2O ice, billion years old - Water in the atmosphere
Only ca. 300 ppm, all trace gases <0.2%
Evidence of water on Mars
Evidence for water present today
* Detection of water in the soil
* Water frost on the surface
* Water-ice clouds
* Water vapour in the atmosphere
* Hydrogen (indicating water) and water at the poles and across the planet’s surface
Evidence for a wet ancient Mars
* Geomorphological: gullies, river channels, streams
* Geological: sedimentary rocks (conglomerates, mudstones), ‘blueberries’, cross/horizontal bedding
* Mineralogical: clay minerals, sulfates, carbonates, iron oxides, silica, salts
Water on Jupiter
- 0.25% of the atmosphere is water (Juno probe, 2020)
- The Galileo probe (1995) measured much less water
during entry, assuming it had sampled an unusually
dry and warm meteorological spot
Water on Jupiter’s moons
95 known moons
3 of the four Galilean moons are icy moons, plus one of the smaller objects:
* Ganymede: ocean sandwiched between up to three ice layers
* Callisto: ice crust up to 200 km thick with a10 km deep subsurface ocean beneath
* Europa: 10 km ice crust showing linea (cryovolcanism or geysirs), 100 km subsurface ocean beneath
* Amalthea: low density indicates high porosity and potential presence of ice
Water on Saturn
- Traces of water in the atmosphere
- Saturn’s rings are made of pieces of ice, dust and rocks
Water on Saturn’s moons
146 known moons
Most or even all of them likely consist of water ice to some extent
* Titan: 80 km ice crust with subsurface ocean, atmosphere with methane clouds and lakes on the surface
* Enceladus: 30-40 km ice crust with 10 km deep subsurface ocean, geysirs,
hydrothermal vents, potentially habitable ocean world
Water on Ice Giants
Uranus
* Mainly made of water, ammonia and methane ices
* 28 known moons, all of them likely consist of water ice and rock
Neptune
* 16 known moons, all of them likely consist of water ice and rock
Water on Dwarf Planets
- Some of the transneptunian dwarf planets have icy moons, e.g. Haumeas‘s moons Hi‘iaka and Namaka
- Icy dwarf planets: Ixion, Orcus, Quaoar, Sedna, Haumea
- Pluto: surface of nitrogen-rich ice and water ice, perhaps subsurface ocean about 100 kilometers deep
- Pluto‘s moon Charon: contains a mixture of ices including water ice, perhaps subsurface water ice
