Lecture 9 - Extrasolar Planets Flashcards
Where and how were planetoids/asteroids formed?
In the gap between Mars and Jupiter. An unstable location because of Jupiter’s gravity.
Jupiter was heavy enough to be differentiated internally so after its collisional disruption, several diff asteroid types were formed.
Why is it not possible for asteroids to be habitable?
- Too small
- No atmosphere
- No liquid medium
- No internal source of heat
- Extreme temperature changes
- Exposed to cosmic rays and UV radiation
What is the important contribution of asteroids?
Brung water to terrestrial planets through impacts
What is the structure of Jovian planets?
- No solid surfaces
- Density progressively increases from gaseous to liquid forms
- Mostly hydrogen and helium with traces of heavy elements
- Solid only found in very (Hydrogen in metallic form)
- Centres are hot (Radiates thermal IR radiation)
How do the clouds and wind on Jupiter move?
In bands due to strong horizontal winds (But there are also vertical winds)
- Some areas are stable low pressure systems that stay fixed (The Red Spot)
Vertical winds cause matter to constantly move through high and low temp, causing electric charge accumulation (lightning) and aurora in the poles from the magnetic field
What are the properties of Jupiter’s clouds?
- Visible, very low temperature at top later
- Made of ammonia, ammonium sulfide, NH4HS (Water vapour found below)
- Overall mainly crystallized ammonia with phosphorus sulfur and hydrocarbon compounds
Why is there no chance of life on Jupiter?
Pros:
- Liquid water present
- Temp and pressure okay in reasonable depth
Cons:
- STRONG VERTICAL WINDS
- Would cause complex molecules to go into deep hot layers where they will get destroyed
- Meteorites carrying life would be thrown down into the heat or up into the cold
How did the moons of Jovian planets form?
They formed as “mini solar-systems” from small gaseous disks orbiting the large solar proto-planetary nebula
Exception: Triton who is on retrograde orbit (Probs captured Kuiper belt object)
Describe the composition of Jovian moons.
Jupiter:
- Only water-ice
- More ice and less density further away from Jupiter (Europe, Ganymede, Callisto)
- High density rock (Io)
Saturn and beyond:
- More water-ice than Jupiter moons
- Methane and other ice also found
Describe the shape of the smaller captured moons of Jovian planets.
Odd shapes because gravity too weak to force rock into sphere
Mainly captured planetoids
What are Jovian planet’s rings made of?
Many orbiting bodies (ranging from boulders to dust)
Saturn’s most prominent with 300,000 km diameter and 0.2-3 km thickness
Where would water ice condense?
Where would methane and ammonia ice condense?
Water ice - Distance of Jupiter from Sun
Methane and ammonia ice - Distance of Saturn and beyond
When do the four Galilean moons rotate and how long is their orbital period?
Rotate about axis once per orbital period.
By the time Ganymede orbits once…
Ganymede orbit - 1 orbit (7 days)
Europa orbit - 2 orbits
Io - 4 orbits
Explain synchronous rotation.
The same side of the moon is always facing towards its planet as it rotates
Explain tidal forces
The moon deforms Earth’s oceans by 2m and land by 1cm because of its gravity.
Causes Earth to lose energy and slow rotation as Earth tries to pull back the tidal bulge that’s leading.
Also pushes Moon away.
This is applicable for any 2-body system
Describe how Io has volcanism
Rock inside is heated to 2000°C, leading to volcanic eruptions and sulfur snow (frozen sulfur dioxide).
Lack of water and extreme volcanism means no life
Explain Io’s tidal heating.
Since the orbit is elliptical, the strength and direction of tidal forces change as distance between Io and Jupiter changes.
Cause interior of Io to get stretched and squeezed every orbit, generating a lot of heat.
What did tidal forces cause Jupiter’s moons to do?
Be in synchronous rotation (1:2:4 in 7 day period)
Periodic alignment pushes them into eccentric orbits (like child on a swing)
The periodic alignment is called orbital resonance
Describe evidence of heating on Iapetus (Saturn’s moon).
Large ridge around moon - Signals massive internal restructuring in response to internal heating
Unknown source of heating tho
Describe Europa’s surface.
- Covered in ice and very bright
- Surface is young because few impact craters and smooth
- Very hard but liquid ocean might be present under ice because of tidal heating of interior
Explain a cause for Europa’s magnetic field
Has magnetic field when core shouldn’t be molten anymore so maybe polar salts and Jupiter’s magnetic field induces currents to flow in it
- This requires salty liquid ocean
Does Europa meet the requirements for life?
- Has source of elements and molecules to build organisms
- Liquid medium
- Source of energy unsure
Maybe chem rxns supplying energy cause diffs in chem potential
Or maybe turbines or volcanic vents to exploit temp differences or diffs in water level (Would be hard to find bcuz very deep tho)
What is chemical disequilibrium?
Rxn proceeding both ways to reach equilibrium must be broken to produce energy
Describe the properties of Ganymede
- Largest moon in solar system
- Surface of hard brittle ice
- Magnetic field (molten core)
- Magnetic field varies w/ Jupiter’s rotation period (Indicating liquid ocean)
- Weaker tidal heating, thicker ice crust
Describe Callisto’s properties
- Water ice and rock, covered w/ old craters
- No differentiation (Not warm enough for melted interior)
- Magnetic field (presence of salty ocean)
Describe the properties of Titan
- Second largest moon of solar system
- Similar to Callisto, mix of ice and rock
- Thick atmosphere w/ organic materials like methane (very high amount) and ethane (But mainly N2; levels similar to Earth)
- 1.5x atmospheric pressure if Earth (Comfortable; planes + balloons can fly here)
What is the chemistry of Titan driven by?
- Presence of ammonia and methane ices (directly condensed from proto-planetary nebula)
- Partial escape of hydrogen from atmosphere
- UV radiation from Sun
What are the dark channels on Titan probably carved by?
Liquid methane or ethane brought there by soft-landing comets
What are the dunes on Titan made of?
Hydrocarbon sediments organized by winds into dunes
Is it possible for Titan to have a subsurface ocean?
Yes
Thru softer tidal interactions
Is Titan good for life?
Very similar to Earth:
- Liquid methane instead of water
- Ice instead of rock
- Slush ice w/ ammonia instead of lava
- Hydrocarbons and smog particles instead of surface dirt
- Has organic molecules
But temps to low - Would make chem rxns and metabolism very slow
Describe the properties of Enceladus
Young, icy surface (reflects 100% of sunlight)
Has ice vents or geysers - Means liquid water under surface
Describe the properties of Triton (Neptune’s Moon)
- Covered by water ice or ammonia ice
- Clouds visible
- Rotates and orbits opposite of everything else (Sign of captured dwarf planet)
Describe the properties of Trans-Neptunian objects
- Have strongly inclined orbits extending far into space
- Several have small moons
- Physical properties poorly known
