jovian planets Flashcards
Jovian planets are radically different in size & copmposition from
terrestrial planets = “gas giants” because
e hydrogen (H
2) & helium (He)
are predominant or important components, though Uranus & Neptune
are also called “ice giants” as they mainly consist of ice-forming
molecules
Jupiter & Saturn are made almost entirely of
f hydrogen (H
2
)
& helium (He)
Jupiter & Saturn have
thick mantles
of metallic H
2.
Uranus & Neptune still have large amounts of
H2 & He
Uranus & Neptune still have large amounts of H2 & He but
less than 50% as they are made primarily of hydrogen compounds, e.g. H 2O, CH 4 & NH 3.
Saturn has a larger ice content than Jupiter, but
Uranus & Neptune have much-much more (>50%!) because of the ices’ increasing
abundance further and further away in the initial Solar nebula
Jovian planets formed in the outer Solar system beyond
the frost line, where it was
cold enough for the more
abundant hydrogen compounds to condense into ices.
All 4 Jovian planets have formed around ice-rich
planetesimals with a similar mass of
~10MEarth that
grew to great size subsequently drawing in H2, He, and
other compounds (self-reinforcing positive feedback).
…again, because of their increasing abundance further and further
away in the primordial Solar nebula
All planets stopped accreting at the same time when the
first solar winds blew remaining material in space
Jovian planets: Origin of their compositional differences—–> Timing
: Planets that start earlier will capture more material before the
first solar winds blow it away
Jovian planets: Origin of their compositional differences—–> Location
Planets formed easier & earlier in a denser part of the nebula (i.e. closer to the Sun) as their cores quickly gathered H2 & He first, and grew faster!
Hydrogen compounds not formed in icy particles if too “close” to the Sun
(i.e. Jupiter & Saturn orbits)
Uranus & Neptune are denser than Saturn! →
because they have
(much) less amounts of low density gases (H2 & He)
The more low density stuff there is, the less dense the overall (i.e. the more
low density material there is in the composition of a planet, the smaller its
final overall density)
Logical that Saturn is less dense than Uranus & Neptune — ;>
Hydrogen compounds, rock, metal are all denser than H2 & He gases
but Jupiter is more dense than Saturn → it doesn’t follow the
pattern… WHY?
Jupiter’s radius is close to the max. possible radius for a ”normal” Jovian planet
Smallest stars are even smaller than Jupiter!
…though some exoplanets can be larger!!
because are
made of much lighter elements, without large, rocky cores
inside.
Jupiter is 3
× more massive but only slightly larger than Saturn → extra mass strongly compresses its interior to much higher
density
Jupiter: Internal structure
No solid surface but fairly distinct interior layers.
Mostly H2 & He except the core.
H2 present in different phases.
Gaseous H2 in outer layer is ~10% of radius = Jupiter’s
atmosphere.
Liquid hydrogen occupies next 10% of Jupiter’s interior
In most of the rest of Jupiter, the extreme T & p force H2 into a compact metallic form! Its molecule & atoms break
into free protons (p+) & electrons (e–)= plasma!
conducts electricity
generates Jupiter’s MF.
At those extreme T & p metallic hydrogen exists as a LIQUID
rather than a solid! (not solid like a metal!).
Core = mix of H2 compounds, rock & metals.
Most probably all mixed together (non-differentiated)
Saturn’s 4 interior layers differ from Jupiter due to its
lower mass & weaker gravity Lower mass phase changes occur deeper in Saturn thicker gaseous layer & thinner & deeply buried metallic hydrogen. Weaker gravity but less dense & fast rotation centrifugal force stronger at equator (more) flattened shape
Because of their rapid rotation and low density,
the Jovian planets are not quite spherical. Saturn shows the biggest difference between its actual shape and a perfect sphere
Uranus & Neptune have almost identical interiors:
Both have rocky cores like Jupiter & Saturn, but this is where
the similarity ends.
p not high enough to form liquid or metallic H2 at all
H2& He layer surrounds odd “oceans” of liquid “ices” of H2 compounds.
All Jovian planets radiate amazing amounts of energy,
more than they receive from the Sun!
Jupiter:, TALK ABOUT ITS RADIATION
Jupiter radiates up to 2× as much energy as it receives
Most of the energy comes from slow contraction of interior
(i.e. Jupiter is still slowly contracting, releasing potential
energy).
This thermal energy heats up from below the atmosphere playing an
important role in its structure & weather.
Besides this blackbody radiation component, part of Jupiter’s emitted
energy does NOT obey Planck’s law → due to synchrotron radiation from the particles trapped in Jupiter’s strong MF
what is synchotron radiation
occurs when a charged particle encounters a strong magnetic field - the particle is accelerated along a spiral path following the magnetic field and emitting radio waves in the process - the result is a distinct radio signature that reveals the strength of the magnetic field
Internal heat – Saturn
Saturn also radiates more energy than it absorbs from the
Sun: it emits 2.3× more energy than it receives (more than
Jupiter!).
Saturn is less massive than Jupiter
should have less leftover
accretion heat and also cannot generate it by (still) contracting!
Potential energy of falling He rain converts into
kinetic energy and its interior heats up (the precipitation of helium inside its metallic hydrogen mantle).
This gradual He rain represents a sort of ongoing differentiation: higher density material (liquid He) is still slowly sinking inside the planet.
Jovian planets: Internal heat - Uranus & Neptune
Uranus lacks a strong internal energy source like Jupiter &
Saturn: radiates only 1.1 × the energy received from the Sun.
Neptune emits 2.7 × more energy as it receives from the Sun; most possibly because of an intense greenhouse effect due to the abundance of CH4 in its composition.
Other possible sources of internal heat:
EITHER resulted from some mysterious still on-going contraction,
OR is accretion heat that should have been radiated b.y.a., like Uranus
(but all or most of it still retained due to extreme greenhouse effect
mentioned above).
Another possible heating mechanism is atmospheric interaction with
ions trapped in its MF.
The internal heat of ALL Jovian planets is the
crucial factor driving atmospheres & in the generation of MFs.
Jovian planets’ atmospheres & weather
- Jupiter
Much thicker (than Earth’s), also much more dynamic (very
strong winds of hundreds of km/h) & turbulent on large
scales (many storms, some larger than Earth!)…
… due to:
its fast rotation (causing a stronger Coriolis force)
splits the large
equator-to-pole circulation cells into many (>3) smaller cells,
the much larger amounts of energy injected in it,
From the bottom = internal heat.
From the top = very energetic particles trapped in its strong MF (besides
solar radiation).
The absence of any solid surface to slow down Jupiter’s storm
systems/spots
can persist for many years (sometimes decades,
even centuries!).
Made up of mainly H2 & some He but many other
components are also present in small amounts, of which H2 compounds are the most important.
Jovian planets’ atmospheres & weather - Jupiter (cont’d)
Structure & temperature variation are very similar to Earth’s.
H2 compounds in Jupiter’s atmosphere form clouds
Cloud
layers correspond to the condensation points of different H2 compounds at various corresponding altitudes.
Each makes clouds of a different color.
Just as for Earth, the atmospheres of Jovian planets are governed
by interactions between sunlight and gases, with Jupiter’s the
best example:
Thermosphere: absorbs solar X-rays AND energetic particles trapped in
the intense Jovian magnetosphere.
Stratosphere: absorbs solar UV
drives chemical reactions that create a
smog-like haze that masks the color & sharpness of clouds & layers below.
Troposphere: greenhouse gases trap heat from BOTH Jupiter & the Sun
Strong convection in the troposphere causes Jovian winds and
weather (strongest near equator).
Jovian planets’ atmospheres & weather
- Saturn
The temperature profile of each Jovian planet determines the color of its appearance→ Various cloud layers form
where a particular gas condenses.
Saturn has the same cloud layers as Jupiter, but they form
deeper (since Saturn is colder on the overall because it’s
farther away from the Sun, despite its larger amount of
internal heat) and spread farther apart (due to its reduced
overall density and lower gravity).
Large tilt & long orbit period should cause long extreme seasons, but
strong internal heat greatly reduces seasonal temperature differences.
Its features are hazy and washed-out because its atmosphere is
thicker: lower mass means lighter gravity
its atmosphere is
less compressed & less dense than Jupiter’s.
Winds at high(er) velocities on Saturn due to more energy
emitted from its core as compared to Jupiter
r
Jovian planets’ atmospheres & weather - Uranus
The atmosphere of Uranus is also mainly composed of H2 with some He but in different proportions (it has more He),
and with much more hydrogen compounds, of which CH4 is
predominant (which gives its pale blue color) and small
amounts of hydrocarbons.
Lacks a strong internal energy source
much less active
atmosphere, with fewer features (storms, eddies, etc.),
however…
Its extremely tilted axis ultimately produces very uneven
warming of its hemispheres
long term N-S flows
across the latitude zones that can drive very fast winds.
The combination of these effects
washed out atmospheric
features, like Saturn’s
Jovian planets’ atmospheres & weather
- Neptune
The atmosphere of Neptune although still mainly made of H2
has even more He than Uranus, also with CH4 and traces of other compounds
Yet something else must contribute to Neptune’s vivid blue color, but
scientists aren’t certain what.
It has the fastest winds in the Solar system, up to ~2,200
km/h!
must be due to a significant internal energy (heat?)
source since its outer atmosphere is one of the coldest places
in the Solar System, with cloud tops at ~55 K.
Possible sources of the impressive internal heat mentioned earlier.
Its internal source of energy powers the atmosphere to produce cyclone-like storms that are not seen on its twin – Uranus- but which, very surprisingly, are short lived.
talk again about the galilean moons
Io is the most volcanically active body in the Solar system.
Europa has one of the smoothest surfaces in the Solar system.
Ganymede is the only satellite in the Solar system known to
possess an magnetosphere (due to a hot core-generated MF).
Callisto is a heavily cratered undifferentiated ice ball.
what about the volcanoes on io surface man
Io’s entire surface is covered with large active volcanoes with so
frequent eruptions that they constantly refresh the surface and
cover any other features (e.g. asteroid craters)
What do the active volcanoes on IO surface mean
Io must be quite hot inside but it should be geologically dead
talk to me about IO tidal forces
Io’s slightly elliptical orbit causes tidal heating due to huge tidal forces
exerted by Jupiter.
Why does Io have an elliptical
orbit?
caused by orbital resonances
the phenomenon of orbital periods falling
into a simple mathematical relation (a
certain ratio) between the 3 inner
Galilean moons, that resulted in periodic
alignments
→ not a coincidence but a direct consequence of (mutual) feedback
from the tides these moons exert on each
other and on Jupiter.
what;s the ice/water world
europa
briefly tell me part 1 europa
Europa is another big moon (similar to Luna’s size), also tidally
locked with Jupiter and with a surface totally made up of water ice
(covered in many places with a reddish layer believed to be the
result of a reaction between salts deposited from water brought to
the surface with the sulphur ejected from Io)
briefly tell me part 2 europa
Lacks large-scale features but has a a fractured, frozen surface,
with patches of different types of areas
All these indicate ongoing cryogeological activity due to tidal stresses
briefly tell me part 3 europa
It must have an interior made hot by tidal heating, but weaker than on Io due to farther distance from Jupiter
