Earth-Saturn Comparisonlwl/classes/astro210/spring05/... · Music: Amy Hit the Atmosphere Night...
14
Mar 16, 2005 Astronomy 210 Spring 2005 Astronomy 210 Section 1– MWF 1500-1550 134 Astronomy Building This Class (Lecture 23): Giant Planets Next Class: Debris Music: Amy Hit the Atmosphere – Counting Crows Night Observation Report and HW 7 due on Friday Mar 16, 2005 Astronomy 210 Spring 2005 Outline • Saturn- The Real Lord of the Rings • Uranus & Neptune Mar 16, 2005 Astronomy 210 Spring 2005 Saturn, Lord of the Rings • Named for the father of the Roman gods • Saturn is very similar to Jupiter – Large planet • Mostly liquid hydrogen – Has a mini-solar system • At least 30 moons • Most are small Equatorial radius 9.45 Earth Cloud-top gravity 0.93 Earth Mass 95.2 Earth Distance from Sun 9.54 AU Eccentricity 0.056 Tilt 26.7 ° Year 29.5 Earth years Solar day 10 hours 14 minutes Least spherical planet, less dense (on average) than water. Earth-Saturn Comparison
Transcript of Earth-Saturn Comparisonlwl/classes/astro210/spring05/... · Music: Amy Hit the Atmosphere Night...
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ast
rono
my
210
Sect
ion
1–M
WF
150
0-15
5013
4 A
stro
nom
y B
uild
ing
Thi
s C
lass
(L
ectu
re 2
3):
Gia
nt P
lane
ts
Nex
t Cla
ss:
Deb
ris
Mus
ic: A
my
Hit
the
Atm
osph
ere
–C
ount
ing
Cro
ws
Nig
ht O
bser
vatio
n R
epor
t and
H
W 7
due
on
Fri
day
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Out
line
•Sa
turn
-T
he R
eal L
ord
of th
e R
ings
•U
ranu
s &
Nep
tune
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn, L
ord
of th
e R
ings
•N
amed
for
the
fath
er o
f th
e R
oman
god
s•
Satu
rn is
ver
y si
mila
r to
Jup
iter
–L
arge
pla
net
•M
ostly
liqu
id h
ydro
gen
–H
as a
min
i-so
lar
syst
em•
At l
east
30
moo
ns•
Mos
t are
sm
all
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Equa
toria
l rad
ius
9.45
Ear
thCl
oud-
top
grav
ity0.
93 E
arth
Mas
s95
.2 E
arth
Dis
tanc
e fr
om S
un9.
54 A
UEc
cent
ricity
0.05
6Ti
lt26
.7 °
Year
29.5
Ear
th y
ears
Sola
r da
y 10
hou
rs 1
4 m
inut
es
Leas
t sp
heric
al p
lane
t,
less
den
se (
on a
vera
ge)
than
wat
er.
Ear
th-S
atur
n C
ompa
riso
n
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Equa
toria
l rad
ius
0.84
Jup
iter
Mas
s0.
30 J
upite
rD
ensi
ty0.
52 J
upite
r
Jupi
ter-
Satu
rn C
ompa
riso
n
Alm
ost
as b
ig a
s Ju
pite
r, b
ut
Muc
h le
ss m
assi
ve!
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Mis
sion
s to
Sat
urn
•T
here
hav
e be
en 4
un
man
ned
spac
ecra
ft
mis
sion
s to
Sat
urn
•Pi
onee
r 11
–Fl
yby
1979
•V
oyag
er 1
–Fl
yby
1980
•V
oyag
er 2
–Fl
yby
1981
•C
assi
ni-H
uyge
ns–
Arr
ived
last
yea
r
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Cas
sini
Mis
sion
•L
aunc
hed
on O
ctob
er 1
5th, 1
997
•A
rriv
ed a
t Sat
urn
on J
uly
1st, 2
004
•W
ill o
rbit
Satu
rn f
or 4
yea
rs, m
akin
g fl
ybys
of
the
plan
et, i
ts r
ings
, and
som
e of
its
moo
ns•
Con
tain
s 12
sci
entif
ic in
stru
men
ts•
Als
o ca
rrie
s th
e H
uyge
ns p
robe
, whi
ch w
as
drop
ped
onto
Tita
n, S
atur
n’s
larg
est m
oon,
at t
he
begi
nnin
g of
the
sem
este
r. R
emem
ber?
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Roa
d to
Sat
urn
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Atm
osph
ere
•C
ompo
sitio
n si
mila
r to
Jup
iter
–M
ostly
hyd
roge
n an
d he
lium
•A
tmos
pher
e m
ore
“spr
ead
out”
–L
ess
grav
ity–
Con
tras
t of
clou
d ba
nds
redu
ced
•W
ind
spee
ds f
aste
st a
t the
equ
ator
–10
00 k
m p
er h
our!
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Dri
ving
Sat
urn’
s W
eath
er
•A
s on
Jup
iter,
Sat
urn’
s in
tern
al h
eat d
rive
s w
eath
er–
Satu
rn r
adia
tes
80%
mor
e he
at th
an it
rec
eive
s fr
om th
e Su
n–
Lik
e Ju
pite
r, S
atur
n is
stil
l con
trac
ting!
–A
s is
con
trac
ts, h
eat i
s pr
oduc
ed
•A
s on
Jup
iter,
sto
rms
are
prod
uced
bet
wee
n cl
oud
band
s–
No
long
last
ing
stor
m li
ke th
e G
reat
Red
Spo
t
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Gre
at W
hite
Spo
t
•A
sea
sona
l sto
rm!
–U
nlik
e Ju
pite
r, S
atur
n do
es
have
sea
sons
•A
n am
mon
ia b
ubbl
e th
at
form
s in
the
nort
hern
-he
mis
pher
e su
mm
er–
Las
ts a
few
mon
ths
–G
ets
wra
pped
aro
und
the
plan
et b
y th
e eq
uato
rial
win
ds
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Int
erio
r
•Si
mil
ar s
truc
ture
to
Jupi
ter’
s–
But
Sat
urn
is le
ss m
assi
ve
–T
he in
teri
or is
less
co
mpr
esse
d
•L
iqui
d m
etal
lic h
ydro
gen
crea
tes
a m
agne
tic f
ield
–30
% w
eake
r th
an E
arth
’s
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Rin
gs
•T
wo
mai
n ri
ngs
–Se
vera
l fai
nter
rin
gs
–E
ach
ring
is d
ivid
ed
into
rin
glet
s
•T
he r
ings
are
thi
n–
Onl
y a
few
tens
of
met
ers
thic
k–ra
zor
thin
!
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Vie
w o
f Sa
turn
’s R
ings
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Mak
eup
of th
e R
ings
•T
he r
ings
of
Satu
rn
are
not
solid
rin
gs–
Mad
e of
icy
rock
s
–1c
m to
10m
acr
oss
•N
ew C
assi
nida
ta s
how
s ri
ng p
artic
le s
ize
vari
es
with
dis
tanc
e fr
om S
atur
n–
Not
e th
e ga
p is
fill
ed w
ith
smal
l par
ticle
s
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Gap
s in
the
Rin
gs
•T
here
are
two
prom
inen
t “ga
ps”
in th
e ri
ngs
–C
assi
nidi
visi
on–
Enc
kega
p
•W
hat c
ause
s th
ese
gaps
?•
Cas
sini
divi
sion
–G
ravi
tatio
nal i
nter
actio
ns w
ith M
imas
, a m
oon
of S
atur
n
•E
ncke
gap
–Sw
ept f
ree
by a
sm
all m
oon
in th
e ga
p
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Dir
ty G
ap
•T
he C
assi
niga
p in
Sa
turn
’s r
ings
is
not
com
plet
ely
empt
y•
Con
tain
sri
ngle
ts o
f “d
irty
dus
t”•
Muc
h le
ss r
efle
ctiv
e th
at th
e m
ain
ring
s
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Pro
met
heu
s
Pan
do
ra
Shep
herd
ing
the
Rin
gs
•T
he F
rin
g is
ext
rem
ely
narr
ow
•It
is k
ept t
hat w
ay b
y a
pair
of
moo
ns th
at
flan
k th
e ri
ng
•K
eep
the
ring
par
ticle
s in
line
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
“Spo
kes”
in th
e R
ings
•Sa
turn
’s m
agne
tic
fiel
d ca
n “l
ift”
pa
rtic
les
out o
f th
e ri
ngpl
ane
•D
ecre
ases
ref
lect
ivity
in
par
ts o
f th
e ri
ngs
•C
reat
es a
“sp
oke”
ef
fect
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Why
so
Rin
gy?
•T
ime
to p
lay
mor
e w
ith ti
dal f
orce
s.
•Im
agin
g a
rubb
le p
ile o
f sm
all r
ocks
that
is o
nly
held
toge
ther
by
grav
ity, t
otal
mas
s m
with
ra
dius
r.
•N
ow, p
ut y
our
pile
in th
e gr
avity
fie
ld o
f a
larg
e ob
ject
, mas
s M
and
rad
ius
R a
t a d
ista
nce
d
•W
hen
does
the
tidal
for
ces
pull
it ap
art?
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tot
ally
Tid
al, A
gain
•C
ompe
titio
n of
sel
f-gr
avity
and
out
war
d tid
es
•C
ompa
re f
orce
s on
a te
st p
artic
le a
t sur
face
of
pile
2 r
mm
GF
test
g=
32
d
rM
mG
Fte
stt=
32
2d
rM
mG
r
mm
Gte
stte
st=
33
2r
mMd
=
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tot
ally
Tid
al, A
gain
•C
ompe
titio
n of
sel
f-gr
avity
and
out
war
d tid
es
•C
ompa
re f
orce
s on
a te
st p
artic
le a
t sur
face
of
pile
•If
den
sitie
s ar
e si
mila
r
•T
hen
⇒
33
2r
mMd
=
33
rm
RM≈
33
2Rd
=R
d3.1
=
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Roc
he L
imit
•If
do
a m
ore
deta
iled
anal
ysis
•A
nyth
ing
insi
de th
is li
mit
is to
rn a
part
.
•N
ote
that
the
ring
s ar
e in
side
this
lim
it, w
hile
the
moo
ns a
re o
utsi
de o
f it.
•R
ings
are
cap
ture
d m
oon
or p
roto
-moo
n th
at n
ever
co
ales
ced
Rd
4.2=
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Moo
ns•
Satu
rn h
as a
larg
e nu
mbe
r of
moo
ns–
At l
east
30
•O
nly
Tita
n is
com
para
ble
to J
upite
r’s
Gal
ilean
moo
ns•
Sm
alle
r m
oons
are
mos
tly ic
e, s
ome
rock
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Odd
Moo
ns
•M
imas
-C
rate
r tw
o-th
irds
its
own
radi
us•
Enc
elad
us-
Fres
h ic
e su
rfac
e, w
ater
vol
cano
es?
•H
yper
ion
–Ir
regu
larl
y sh
aped
•Ia
petu
s-
Hal
f its
sur
face
is
10x
dark
er th
an th
e ot
her
half
•P
hoeb
e-
Orb
its S
atur
n ba
ckw
ards
Mimas
Phoebe
Hyperion
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Satu
rn’s
Odd
Moo
ns
Bra
nd n
ew im
ages
fro
m
Mar
ch 9
thE
ncel
adus
has
ate
nuou
s at
mos
pher
e
Phoebe
Hyperion
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tita
n
Tita
n’s
atm
osph
ere
•Sa
turn
’s la
rges
t moo
n–bi
gger
than
Mer
cury
.•
2nd
larg
est m
oon
in th
e so
lar
syst
em a
fter
G
anym
ede.
•O
nly
moo
n to
hav
e a
dens
e at
mos
pher
e–
Den
se n
itrog
en/m
etha
ne a
tmos
pher
e (b
asic
ally
sm
og)
–S
mal
l gre
enho
use
effe
ct–
85%
nitr
ogen
•co
mpo
sitio
n of
anc
ient
Ear
th
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tita
n
Tita
n’s
atm
osph
ere
•A
tmos
pher
ic p
ress
ure
is 1
.5 ti
mes
Ear
th’s
•L
iqui
d/ic
e hy
droc
arbo
ns?
•O
rgan
ic c
ompo
unds
–li
fe?
•Pr
obab
ly n
ot –
too
cold
: 95
K•
May
be
a “d
eep
free
ze”
of th
e ch
emic
al
com
posi
tion
of a
ncie
nt E
arth
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Pie
rcin
g th
e Sm
og
•C
assi
niha
s sp
ecia
l inf
rare
d ca
mer
as to
see
thro
ugh
Tita
n’s
smog
•G
reen
are
as a
re w
ater
ice
•Y
ello
w-o
rang
e ar
eas
are
hydr
ocar
bon
ice
•W
hite
are
a is
a m
etha
ne c
loud
ov
er th
e so
uth
pole
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Cas
sini
-Huy
gens
Huy
gens
Pro
bede
scen
t to
Tita
nJa
n 14
, 200
5
Arr
ival
at S
atur
nJu
ly 1
, 200
4
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Map
ping
Tita
n
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Map
ping
Tita
n
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tita
n•
N2
cam
e fr
om a
mm
onia
(N
H3)
–co
mm
on in
out
er s
olar
sys
tem
•
Seco
nd m
ost a
bund
ant c
ompo
nent
is m
etha
ne (
natu
ral g
as)
-O
ne o
ptio
n is
UV
+ m
etha
ne
hydr
ocar
bons
(e.
g., e
than
e)-
The
n, e
than
e co
nden
ses
and
rain
s do
wn
on T
itan’
s su
rfac
e•
So, i
t mig
ht h
ave
liqui
d et
hane
or
met
hane
lake
s/oc
eans
?•
Man
y or
gani
c co
mpo
unds
sho
uld
be in
atm
osph
ere–
redu
cing
at
mos
pher
e.•
If li
fe e
xist
s he
re, t
hen
it w
ill c
hang
e ou
r w
ater
–cha
uvin
istic
idea
s.
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Dis
cove
ry o
f U
ranu
s
•D
isco
vere
d by
acc
iden
t by
Will
iam
Her
sche
l in
1781
•N
amed
for
the
fath
er o
f Sa
turn
•Fi
rst p
lane
t dis
cove
red
sinc
e an
cien
t tim
es
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Dis
cove
ry o
f N
eptu
ne•
Obs
erva
tions
sho
wed
that
U
ranu
s w
as n
ot o
rbiti
ng th
e w
ay N
ewto
n pr
edic
ted
•T
wo
scie
ntis
ts p
redi
cted
a
new
pla
net,
Nep
tune
–W
ithin
1 d
egre
e of
whe
re it
was
fo
und
in 1
846
•A
triu
mph
of
New
ton’
s L
aws!
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Equa
toria
l rad
ius
4.01
Ear
thCl
oud-
top
grav
ity0.
79 E
arth
Mas
s14
.5 E
arth
Dis
tanc
e fr
om S
un19
.2 A
UTi
lt of
rot
atio
n ax
is98
deg
rees
Year
84 E
arth
yea
rsSo
lar
day
17 h
ours
14
min
utes
(on
its
side
)
Ura
nus-
Ear
th C
ompa
riso
n
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Equa
toria
l rad
ius
3.88
Ear
thCl
oud-
top
grav
ity1.
12 E
arth
Mas
s17
.1 E
arth
Dis
tanc
e fr
om S
un30
.1 A
UTi
lt of
rot
atio
n ax
is29
.6 d
egre
esYe
ar16
4.8
Eart
h ye
ars
Sola
r da
y16
hou
rs 7
min
utes
Nep
tune
-Ear
th C
ompa
riso
n
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Orb
it of
Ura
nus
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
The
Orb
it of
Ura
nus
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Atm
osph
eres
of
Ura
nus
and
Nep
tune
•C
ompo
sed
of a
bout
90%
hyd
roge
n, 9
% h
eliu
m, 1
%
met
hane
and
sm
all a
mou
nts
of a
cety
lene
and
oth
er
hydr
ocar
bons
•T
empe
ratu
res
are
so lo
w, t
hat m
etha
ne ic
e cr
ysta
ls f
orm
cl
ouds
•M
etha
ne a
bsor
bs r
ed li
ght,
mak
ing
the
plan
ets
appe
ar
blui
sh•
The
atm
osph
eres
are
arr
ange
d in
to c
loud
ban
ds r
unni
ng a
t co
nsta
nt la
titud
es–
Sim
ilar
to th
e or
ient
atio
n of
the
clou
d ba
nds
seen
on
Jupi
ter
and
Satu
rn
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Atm
osph
ere
of U
ranu
s
•W
hen
Voy
ager
2 v
isite
d U
ranu
s in
198
6, it
saw
a
feat
urel
ess
pale
blu
e cl
oud
laye
r
•H
igh
cont
rast
im
ages
sho
w
clou
d ba
ndin
g
•W
ind
spee
ds
of 3
50 k
m/h
r
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Stor
ms
on U
ranu
s
•In
the
1990
’s, H
ubbl
e ob
serv
atio
ns o
f U
ranu
s fo
und
stor
ms!
•W
hy n
one
befo
re?
•U
ranu
s’ o
dd s
easo
ns m
ay b
e th
e ca
use
•T
rigg
ered
by
sunl
ight
re
achi
ng a
reg
ion
of th
e pl
anet
for
a f
irst
tim
e in
de
cade
s?
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Stor
ms
on U
ranu
s•
In th
e 19
90’s
, Hub
ble
obse
rvat
ions
of
Ura
nus
foun
d st
orm
s!•
Why
non
e be
fore
?•
Ura
nus’
odd
sea
sons
may
be
the
caus
e•
Tri
gger
ed b
y su
nlig
ht
reac
hing
a r
egio
n of
the
plan
et f
or a
fir
st ti
me
in
deca
des?
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Nep
tune
’s A
tmos
pher
e•
Whe
n vi
site
d by
Voy
ager
2
in 1
989,
Nep
tune
sho
wed
m
ore
feat
ures
than
Ura
nus
•L
arge
sto
rms
–G
reat
Dar
k Sp
ot–
Lik
e th
e G
reat
Red
Spo
t?–
Dis
appe
ared
by
1994
•W
hite
clo
uds
–Fr
ozen
met
hane
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Met
hane
Clo
uds
of N
eptu
ne
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Wat
er W
orld
s
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Mag
netic
Fie
lds
•O
n bo
th U
ranu
s an
d N
eptu
ne–
Com
pres
sed
wat
er m
antle
con
duct
s el
ectr
icity
–R
apid
rot
atio
n (a
bout
17
hour
s)
•G
ener
ates
ver
y od
d m
agne
tic f
ield
s–
Off
-cen
ter
& h
ighl
y til
ted
to th
e pl
anet
s’ s
pin
axes
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ura
nus’
Rin
gs•
Dis
cove
red
1977
fro
m E
arth
dur
ing
occu
ltatio
n of
a s
tar
•L
ater
obs
erve
d cl
ose-
up b
y V
oyag
er 2
(19
86)
•R
ings
are
dar
k, n
arro
w, d
usty
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Ura
nus’
Rin
gs•
Dis
cove
red
1977
fro
m E
arth
dur
ing
occu
ltatio
n of
a s
tar
•L
ater
obs
erve
d cl
ose-
up b
y V
oyag
er 2
(19
86)
•R
ings
are
dar
k, n
arro
w, d
usty
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Voy
ager
2
Nep
tune
’s R
ings
•T
hin
and
dark
•L
ike
Ura
nus’
ri
ngs
•Se
en b
y V
oyag
er 2
in
198
9
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Nep
tune
’s R
ings
•N
eptu
ne’s
ou
term
ost r
ing
appe
ars
to b
e tw
iste
d!•
Cau
sed
by a
gr
avita
tiona
l in
tera
ctio
n w
ith
one
of it
s m
oons
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Tita
nia
(larg
est)
Mira
nda
(sm
alle
st
of th
e m
ajor
s)
Moo
ns o
f U
ranu
s•
5 in
term
edia
te s
atel
lites
, non
e G
alile
an-s
ized
–T
itani
a, A
riel
, Um
brie
l, O
bero
n, M
iran
da–
Com
pose
d of
50%
roc
k, 5
0% ic
e
•10
min
or o
nes
disc
over
ed b
y V
oyag
er 2
•5
addi
tiona
l min
or o
nes
disc
over
ed s
ince
then
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Moo
ns o
f U
ranu
s
•M
iran
da’s
pat
chw
ork
appe
aran
ce s
ugge
sts
a ca
tast
roph
ic im
pact
•M
iran
da w
as
com
plet
ely
shat
tere
d,
then
rea
ssem
bled
it
self
•D
id a
sim
ilar
impa
ct
flip
Ura
nus
on it
s si
de?
Mar
16,
200
5A
stro
nom
y 21
0 Sp
ring
200
5
Moo
ns o
f N
eptu
ne
•E
ight
moo
ns k
now
n–
2 in
term
edia
te s
ized
, Ner
eid
& P
rote
us
•1
Gal
ilean
-siz
ed, T
rito
n–
Thi
n ni
trog
en a
tmos
pher
e–
50%
roc
k, 5
0% ic
e–
Surf
ace
froz
en
met
hane
/nitr
ogen
–E
vide
nce
of g
eolo
gic
activ
ity (
few
cra
ters
)–
Orb
its N
eptu
ne
back
war
ds
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