Planets & Life

Planets & Life

PHYS 214

PHYS 214

Dr Rob Thacker

Dr Rob Thacker

Dept of Physics (308A)

Dept of Physics (308A)

thacker@

astro.queensu.ca

thacker@

astro.queensu.ca

Please start all class related emails with

Please start all class related emails with ““214:

214:””

Midterm

details

Midterm

details

��Walter Light Hall

Walter Light Hall Rm

Rm

205 9:30

205 9:30 ––

10:30 (so

10:30 (so

within our usual class slot)

within our usual class slot)

��Half multiple choice, half short answ

erHalf multiple choice, half short answ

er

��On the material in weeks 1

On the material in weeks 1-- 55

��On conflicts:

On conflicts:

��““If a conflict arises with one course scheduling their

If a conflict arises with one course scheduling their

exam

outside of their usual slot, then it is the

exam

outside of their usual slot, then it is the

responsibility of the instructor scheduling outside of

responsibility of the instructor scheduling outside of

the slot to m

ake accommodations for students

the slot to m

ake accommodations for students

unable to attend due to a conflict

unable to attend due to a conflict ””

Homework

Homework

��If you haven

If you haven’’ t already handed in assignment 1

t already handed in assignment 1

please do so at the end of class

please do so at the end of class

��Assignment 2 will be posted this afternoon

Assignment 2 will be posted this afternoon

��Questions on stars, radiation from stars & habitable

Questions on stars, radiation from stars & habitable

zones

zones

Rem

embe

r: no lectur

e Frida

y

Today

Today’’ s Lecture

s Lecture

��The

The Jovian

Jovian

planets

planets

��Brief discussion of the space

Brief discussion of the space --craft we have sent to these

craft we have sent to these

planets

planets

��Physical characteristics of the

Physical characteristics of the Jovian

Jovian

planets

planets

��Possibility of life?

Possibility of life?

We ar

en’t going

to the star

s soon

. If w

e wan

t to loo

k for life

on othe

r plan

ets,

then

our

own solar system

is the on

ly place w

e can send

probe

s.

Goo

gle vide

o ha

s copies of “V

oyag

e to the

Plane

ts”a fact bas

ed but ficitiona

laccoun

t

of the

possibilit

y of hum

ans trav

ellin

gto all

the plan

ets.

Definitely worth a w

atch.

Mass distribution in the solar system

Mass distribution in the solar system

0.0000001%

?0.0000001%

?Interplanetary medium

Interplanetary medium

0.0000001%

?0.0000001%

?Meteroids

Meteroids

0.0000002%

?0.0000002%

?Minor planets

Minor planets

0.00005%

0.00005%

Satellites (moons)

Satellites (moons)

0.01%

0.01%

Comets

Comets

0.135%

0.135%

Planets

Planets

99.85%

99.85%

Sun

Sun

Contribution

Contribution

Object

Object

Jupiter is m

ore than

twice as

mas

sive as the rest of the plan

etscombine

d.

Comparison: Orbital data

Comparison: Orbital data

��Orbit R: Period P: Mass M:

Orbit R: Period P: Mass M:

(in AU) (in years) (

(in AU) (in years) ( ��

Earth)

Earth)

��Jupiter 5.2

Jupiter 5.2

1212318

318

��Saturn

Saturn

9.6

9.6

30309494

��Uranus

Uranus

19.2

19.2

85851515

��Neptune 30.1

Neptune 30.1

165

165

1717

Nep

tune gets 1/3

02=1/9

00th

of th

e radiation that the

Earth

gets

Voyagers 1 & 2

Voyagers 1 & 2

��Unmanned probes sent to O

uter solar system

Unmanned probes sent to O

uter solar system

(launched 1977)

(launched 1977)

��Voyager 1 visited Jupiter & Saturn

Voyager 1 visited Jupiter & Saturn

��Voyager 2 visited Jupiter, Saturn, U

ranus,

Voyager 2 visited Jupiter, Saturn, U

ranus,

Neptune

Neptune

��Each probe carries a `G

olden Record

Each probe carries a `G

olden Record’’

containing inform

ation about the Earth

containing inform

ation about the Earth

��Also includes cartridge and needle needed to m

ake a

Also includes cartridge and needle needed to m

ake a

player for the record

player for the record

Voyager trajectories

Voyager trajectories

Although lau

nch

ed a

2 w

eeks after Voyag

er 2

Voyag

er 1 rea

ched

Jupiter

first

Voyag

er 2 use

d a slingsh

ot

from S

aturn

to pro

pel it

on toward U

ranus & N

eptune

(took 12 yea

rs to rea

ch N

eptune!)

The Golden Record

The Golden Record

��Content decided upon by a

Content decided upon by a

committee headed by Dr

committee headed by Dr

Carl

Carl Sagan

Sagan

��115 images, followed by

115 images, followed by

greetings in 56 languages, a

greetings in 56 languages, a

series of sounds of Earth

series of sounds of Earth

and then 90 minutes of

and then 90 minutes of

music

music

��Sounds include

Sounds include

��Dog

Dog……

��Chimp

Chimp……

Voyag

ers still tak

e 40,0

00 yea

rs to trav

el 1

.6 light yea

rs! U

nbelieva

bly un

likely to be pick

ed up!

Galileo

Galileo

(Jupiter)

(Jupiter)

��More recent spacecraft (launched 1989) which orbited

More recent spacecraft (launched 1989) which orbited

around Jupiter until 2003

around Jupiter until 2003

��It was destroyed to prevent the possible contamination of the

It was destroyed to prevent the possible contamination of the

Europa

Europa , one of Jupiter

, one of Jupiter’’ s m

oons that

s moons that harbours

harboursliquid water

liquid water

under an ice surface

under an ice surface

��Deployed probe into Jupiter

Deployed probe into Jupiter’’ s atm

osphere

s atmosphere

Even with a dam

aged

antenna it has relayed

back some im

portant

data and beautiful

pictures (right: Jupiter’s

rings)

Cassini

Cassini --Huygens

Huygens

(Saturn)

(Saturn)

��Collaboration between N

ASA and European

Collaboration between N

ASA and European

Space agency (ESA)

Space agency (ESA)

��NASA built the

NASA built the Cassini

Cassiniorbiter

orbiter

��ESA built the

ESA built the Huygen

Huygen’’ sslander

lander

(landed on Titan)

(landed on Titan)

��Launched in 1997, took 4 gravity assists to get it

Launched in 1997, took 4 gravity assists to get it

to Saturn

to Saturn

��Also included the heaviest payload of plutonium

Also included the heaviest payload of plutonium

ever launched in a rocket (36.5 kg!)

ever launched in a rocket (36.5 kg!)

A few thoughts about interplanetary

A few thoughts about interplanetary

exploration

exploration ––is it expensive?

is it expensive?

��Cost of Galileo m

ission ~ $1.5 billion (over 10

Cost of Galileo m

ission ~ $1.5 billion (over 10

years)

years)

��Cost of

Cost of Cassini

Cassini --Huygens mission = $3.26 billion

Huygens mission = $3.26 billion

(over a similar period)

(over a similar period)

��US annual G

DP ~ $10 trillion

US annual G

DP ~ $10 trillion

��US defense budget around $400 billion

US defense budget around $400 billion

��NASA Budget per year around $16 billion

NASA Budget per year around $16 billion

��Cost of entire Apollo project ~ $150 billion in

Cost of entire Apollo project ~ $150 billion in

today

today’’ s dollars

s dollars

You

decide…

Jupiter

Jupiter

Very strong banding

of clouds

in equatorial

region

(Pictu

re fro

m the

Cas

sini`M

illeniu

mfly-b

y’)

Great R

ed S

pot

Jupiter Facts

Jupiter Facts

��Diameter: 142,000 km (11

Diameter: 142,000 km (11��

Earth)

Earth)

��Rotation period is

Rotation period is a

bout

abou

t9.8 hours (very fast)

9.8 hours (very fast)

��Different latitudes rotate at different rates

Different latitudes rotate at different rates

(slower at poles, faster at equator)

(slower at poles, faster at equator)

��`Surface*

`Surface*’’gravity is 2.5

gravity is 2.5��

that of Earth

that of Earth

��Escape velocity is 6 tim

es that of Earth

Escape velocity is 6 tim

es that of Earth

��Magnetic field is 14

Magnetic field is 14��

stronger than Earth

stronger than Earth’’ ss

��Radiates more energy at infrared wavelengths

Radiates more energy at infrared wavelengths

than it receives from the Sun

than it receives from the Sun ––

slowly

slowly

collapsing and releasing energy

collapsing and releasing energy

*gra

vity at the to

p of the atmosp

her

e

Great Red Spot

Great Red Spot

Gre

at R

ed S

pot an

d

Earth

(to

sca

le)

Red

Spot is an

ancien

t hurricanein

Jupiter’s atm

osp

her

e –

Win

d spee

ds 650 km s

-1

Diameter

is over

twice th

at of Earth

Circu

lation ban

ds sh

ow it is

rotating

Origin of colou

ris not fully und

erstoo

d, m

ay be do

wn to red

pho

spho

rus

Jupiter

Jupiter ’’s Atm

osphere: Convection

s Atm

osphere: Convection

��Zones

Zones --light (heating,

light (heating,

high pressure), Belts

high pressure), Belts --

dark (cooling, low

dark (cooling, low

pressure)

pressure)

��Zones flow in the

Zones flow in the

opposite direction to

opposite direction to

belts

belts

Zones

, belts w

rap aro

und the planet bec

ause

of the fast rotation

Cloud motion

Cloud motion

��Clip shows projected surface of Jupiter over 10

Clip shows projected surface of Jupiter over 10

days, as shot by

days, as shot by Cassini

Cassini --Huygens probe

Huygens probe

New

New ““Junior

Junior ””

Red Spot

Red Spot

App

eared in 2

006, an

d seem

s to hav

e be

en formed

by the merger of

two othe

r storms

Jupiter

Jupiter ’’s Atm

osphere

s Atm

osphere

�84% H

ydrogen, 15%

Helium

�Very chem

ically complex,

subtle reactions depend on

temperature and pressure

�We see the upper N

H3

(ammonia) ice clouds as

white regions

�The am

monium

hydrosulfide (N

H4H

S) ice

clouds are seen as dark

regions

Life on Jupiter?

Life on Jupiter?

��In the 1970

In the 1970’’ s (prior to Voyager missions)

s (prior to Voyager missions) Sagan

Sagan

&

& Salpeter

Salpeter

hypothesized that ammonia based life could evolve in Jupiter

hypothesized that ammonia based life could evolve in Jupiter’’ s s

atmosphere

atmosphere

��The idea was adopted by many science fiction authors but quickly

The idea was adopted by many science fiction authors but quickly

Voyager data proved the hypothesis fundam

entally flawed

Voyager data proved the hypothesis fundam

entally flawed

��In practice this seems incredibly unlikely for the following

In practice this seems incredibly unlikely for the following

reasons:

reasons:

��Winds range from 200 to 1600 km

hWinds range from 200 to 1600 km

h-- 11

��Tem

perature ranges are vast, from

Tem

perature ranges are vast, from --167

167°°C to 0

C to 0°°CC

��Where the temperature reaches 0

Where the temperature reaches 0°°C the pressure is equivalent to being

C the pressure is equivalent to being

under 2 m

iles of water on the Earth

under 2 m

iles of water on the Earth

��Large amounts of electrical discharge

Large amounts of electrical discharge

Contribution of Jupiter to life on

Contribution of Jupiter to life on

Earth

Earth

��Jupiter

Jupiter’’ s gravitational pull is sufficiently large to deflect

s gravitational pull is sufficiently large to deflect

a large fraction of comets and

a large fraction of comets and planetesimals

planetesimalsheading for

heading for

the inner solar system

the inner solar system

��This helps reduce the probability of an im

pact event

This helps reduce the probability of an im

pact event

that could wipe out life on Earth

that could wipe out life on Earth

��However, Jupiter cannot be too m

assive as some

However, Jupiter cannot be too m

assive as some

comets must reach the primordial E

arth to supply it

comets must reach the primordial E

arth to supply it

with water

with water

��The balance between having enough m

ass and having to

The balance between having enough m

ass and having to

much m

ass is part of the Rare Earth hypothesis

much m

ass is part of the Rare Earth hypothesis

Jovian

JovianSatellites

Satellites

��Jupiter has at least 60 m

oons of sizes

Jupiter has at least 60 m

oons of sizes

greater than 3km

greater than 3km

��However there are 4 major satellites

However there are 4 major satellites

(diameter greater than 3000km)

(diameter greater than 3000km)

��Io,

Io, Europa

Europa , G

anym

ede,

, Ganym

ede, Callisto

Callisto

��Io shows extrem

e volcanic activity

Io shows extrem

e volcanic activity

due to stresses caused by

due to stresses caused by Jupiters

Jupiters

tidal field

tidal field

��Ganym

ede,

Ganym

ede, Callisto

Callisto

and

and Europa

Europaall

all

show evidence of liquid water

show evidence of liquid water

beneath their surfaces

beneath their surfaces

��The presence of trace am

ounts of

The presence of trace am

ounts of

organic m

olecules have been found

organic m

olecules have been found

on G

anym

ede and

on G

anym

ede and Callisto

Callisto

Europa

Europa ��

Frozen surface of water ice

Frozen surface of water ice

(100 km thick?)

(100 km thick?)

��Surface temperature ~

Surface temperature ~ --160 C

160 C

��Very few surface craters

Very few surface craters

indicates a fairly new

surface

indicates a fairly new

surface

��No organic m

olecules have

No organic m

olecules have

been detected on surface, but

been detected on surface, but

we don

we don’’ t know about under the

t know about under the

ice sheet

ice sheet

��Possibility of subsurface ocean

Possibility of subsurface ocean

due to heat from tidal heating

due to heat from tidal heating

of the planet caused by Jupiter

of the planet caused by Jupiter

��Requires a probe to be sent to

Requires a probe to be sent to

test the idea

test the idea

��Water + heat + organic

Water + heat + organic

molecules=

possibility of life?

molecules=

possibility of life?

We’ll

spen

d a lectur

e look

ing at this po

ssibilt

y…

Saturn

Saturn

Saturn

fro

m V

oyag

er 1 after

it’s fly-b

y

Saturn Facts

Saturn Facts

��Diameter 120,000 km

Diameter 120,000 km

��Saturn is

Saturn is less de

nse

less den

se than water

than water

��Rotation period about 10 hours

Rotation period about 10 hours

��Escape velocity is about 3

Escape velocity is about 3��

Earth

Earth’’ ss

��`Surface

`Surface ’’gravity: approx same as Earth

gravity: approx same as Earth

��Ring system

form

ed from break

Ring system

form

ed from break-- up of

up of planetesimals

planetesimals

��Has very large satellite system like Jupiter and also

Has very large satellite system like Jupiter and also

emits more energy at infrared wavelengths than it

emits more energy at infrared wavelengths than it

receives from the Sun

receives from the Sun

Saturn

Saturn’’ s Atm

osphere

s Atm

osphere

��92.4 %

Hydrogen, 7.4 %

92.4 %

Hydrogen, 7.4 %

Helium

Helium

��Less Helium because it is

Less Helium because it is

condensing out and raining

condensing out and raining

down on the center of the

down on the center of the

planet

planet

��Very similar to the

Very similar to the Jovian

Jovian

atmosphere

atmosphere

��Equally inhospitable

Equally inhospitable

��Less dense, so pressure

Less dense, so pressure

does not rise as fast with

does not rise as fast with

depth

depth

Titan

eclipsing

the

Sun

, the sm

all moo

n is E

ncelad

us

Aurora on Saturn

Aurora on Saturn

Pictu

re fro

m the

Hubble S

pac

e

Teles

cope

Occ

ur on

oth

er planets

too

Titan

Titan

��Titan is the only m

oon in the solar system

with a thick

Titan is the only m

oon in the solar system

with a thick

atmosphere

atmosphere

��Visible wavelengths do not penetrate the haze

Visible wavelengths do not penetrate the haze ––high

high albedo

albedoso Titan is

so Titan is

colder than we might expect

colder than we might expect

��Surface temperatures around

Surface temperatures around --179

179°°CC

��Liquid m

ethane precipitation?

Liquid m

ethane precipitation?

��The Huygens probe landed on the surface and sent some

The Huygens probe landed on the surface and sent some

stunning images back

stunning images back

��Strong evidence for lakes of hydrocarbons

Strong evidence for lakes of hydrocarbons ––first liquid bodies observed

first liquid bodies observed

beyond Earth

beyond Earth

��Evidence of erosion

Evidence of erosion

��Other than tem

perature Titan has a number of similarities with

Other than tem

perature Titan has a number of similarities with

primordial Earth

primordial Earth ––

we

we ’’ll spend a lecture looking at this in m

ore

ll spend a lecture looking at this in m

ore

detail

detail

Artist’s im

pression

of Titan

’s sur

face

Sou

nd of Titan

from H

uygens

probe

Uranus

Uranus

��HST picture at infrared wavelength

HST picture at infrared wavelength

Very plain at

visible w

avelen

gths!

Clo

uds

Uranus Facts

Uranus Facts

��Axial tilt 98

Axial tilt 98o

o --poles almost lie on ecliptic

poles almost lie on ecliptic

��Diameter: about 50,000 km

Diameter: about 50,000 km

��Rotation period: about 17 hours

Rotation period: about 17 hours

��Escape velocity about 2

Escape velocity about 2��

Earth

Earth’’ ss

Neptune

Neptune

Rin

g system

not

visible on this pictu

re

Neptune Facts

Neptune Facts

��Discovered in 1846 following realization

Discovered in 1846 following realization

that Uranus

that Uranus ’’s orbit was being perturbed

s orbit was being perturbed

��Diameter: 50,000 km

Diameter: 50,000 km

��Rotation period: 17 hours

Rotation period: 17 hours

��Slightly more m

assive than Uranus

Slightly more m

assive than Uranus

��Exhibits massive storm

systems

Exhibits massive storm

systems ““Great

Great

dark spot

dark spot ””

but dissipation occurs rapidly

but dissipation occurs rapidly

(visible in 1989 but not 1994)

(visible in 1989 but not 1994)

Trito

n

Summary of lecture 13

Summary of lecture 13

��Life evolving in the

Life evolving in the Jovian

Jovian

planets

planets

them

selves seems virtually impossible

them

selves seems virtually impossible

��However, a number of satellites show

However, a number of satellites show

evidence for liquid water, heat and organic

evidence for liquid water, heat and organic

monomers which together could form

the

monomers which together could form

the

basis of life

basis of life

Next lecture

Next lecture

��Terrestrial planets

Terrestrial planets