good morning
welcome to goddard space flight center
and next edition of our comet update for
thursday
uh this morning we would uh have opened
up as you saw with
the first real color image from the
hubble space telescope of the impacts
and that was the g
fragment impact site we'll roll that
again later
uh today we will tell you more about
that as well as give you a look at comet
fragments q1
and 2 and that's 10 hours before impact
and just after
impact and we'll bring you some news
from comet observers from around the
world
including a looks at fragment r and a
surprising report on fragment
uh m impact of fragment m which had
totally disappeared from vue a couple of
months ago
and we'll have more information on on
that and and what's coming up later
in the next few days uh following uh
the presentations let me introduce a
panel now to my left
dr hal weaver a scientist at the space
telescope science institute
and a leader of the team using hubble's
wide field planetary camera 2
and faint object spectrograph to observe
the structure and breakup of the comet
to his left dr rita bibi a planetologist
of long standing at new mexico state
university
and a member of the whitefield planetary
camera 2 team observing
jupiter's atmosphere and back with us
again today
dr eugene shoemaker coming back for
another day a long time comment watcher
and co-discoverer of the comet shoemaker
levy 9 with the lowell observatory in
the u.s geological survey
to his left dr lucy mcfadden also back
with us again today
from the university of maryland
university of california
and she's the coordinator of the
worldwide comment observing campaign
and a visiting professor at the
university of maryland
and to her left david levy as
co-discoverer of the comet and he is
author of some
recently published books and uh at this
point
i'd like to uh turn this over to gene
shoemaker
thanks don uh we'll give just a little
bit of
an update on the status of the fragments
uh one that's a particular interest to
me is that
keck reported seeing the impact of
fragment
m which had actually disappeared from
view for a while
and there's been great debate as to what
do these things actually
dissipate or is there really something
is there really a piece there that
simply stop being active
uh and i think both both hal and i have
had the
have been on the side that yes there's
really something there it's just sort of
turned off
and so both of us are very pleased with
that report
and then hal is going to give our
last look at the two pieces of fragment
q1 and q2 what was happening to them
as we were watching the comet going in
hell
that's right we might call this show
right now watch this comet die
because the hubble most of this week has
spent its time
focused on jupiter watching the
spectacular display that you've
talked about all this week but we can't
forget about our kamikaze comet
of course that's the source of all the
activity we're seeing and we really
can't understand what's happening on
jupiter
until we understand what it is that went
plowing into jupiter
and as don was saying earlier
the hubble actually swung off of jupiter
and observed
the very interesting q region in the
comet this is one of the brighter
regions
only 10 hours prior prior to its plunge
into jupiter
now i thought before i showed you the
pictures of
the final pictures of q that i would
step back and just
give you a status report on the comet
gives you sort of a road map
if we can show the first picture
i think most of you recognize now we've
been lettering these
commentary nuclei from a through w
they're 21 pieces and
a was the first one to go in on saturday
and we're now up to just in front of the
s impact and s is going to be going in
about three hours from now
about about 11 am and you see
a couple couple of pieces before s you
see the q region
that was a has always been recognized as
a very interesting region
but if we go to the next graphic you'll
see
what is left if we can dissolve to the
next graphic
okay we 16 of the pieces have gone and
we got five left to go
and q as i said has always been
recognized as one of the more
interesting
pieces of the comment and if we can go
to to the next graphic showing
the q region as we saw it in late march
you'll see why it was so interesting
i think having it
could you roll the next graphic please
um you can kind of make out here why q
is special
it's obviously not okay this is showing
what's left most of the comment is gone
most of it has died away and
unfortunately we only have these few
pieces left for those of us who like
comments
now if you can go on to the next the
next picture
and this is how q appeared to the left
this is how q appeared
in late march there was actually four
pieces in the field at that point
q1 q2 and then
down below those are the so-called p
region and
q you can see is a double object and
that's what made it so interesting
most of the fragments in the comet had
remained stable
for about two years not showing any
evidence of breakup
but q from the time that we started
observing it
they had these two bodies close to each
other indicating that there was a
subsequent
a fragmentation of cues subsequent to
the the breakup of the original body
and based on that
some of us thought that maybe q was a
good candidate for breaking up further
as it came into jupiter
that's why we wanted to take the last
look because the amount of
energy that's impact you know that goes
into jupiter's atmosphere and causes
these explosions depends on how much
mass and if this thing is going to be
breaking up into small pieces before it
goes into jupiter you get much less bang
so yesterday morning we took the picture
to the right
which shows how dramatically stretched
out
the comet is getting just before going
into jupiter it stretches out
along the direction along the path of
its motion into jupiter
and you see that uh q1 and q2 the comey
which is the dust around the comet is
getting stretched out along the
direction of motion
but but the fragments are hanging in
there just 10 hours prior to the impact
they're still hanging in there
indicating that there should be a
substantial splash when it hits jupiter
now at that point uh i think we're ready
to turn it over to rita and find out
exactly what happened as the q impacts
went into jupiter
i know you're all waiting for the triple
whammy
actually from what he's just told you
it's a quadruple miami
because we have q1 q2 and then we have
rns going in the planet rotates once
every 10 hours
q2 and q1 were
scheduled to arrive so that they should
have impacted about 12 degrees apart
and then almost 10 hours later
r comes in and almost 10 hours later s
comes in
so that the this impact site will have
only 10 hours to recover
from site to site the site could i have
my first graphic please
could i have the next one please
next graphic please next graphic please
okay
uh we'll start with the one that was
displayed at uh
when we first came in uh that one showed
the g impact site about an hour and 45
minutes
after that the g had impacted
d had impacted considerably early but d
was quite a small one it's just a small
spot sitting off to the side
now could i have the previous graphic
and we'll see the same region
61 hours later could we go back to the
other color graphic
please
so here you see the development site d
is the impact site uh in the upper
portion
and l has arrived in the interim
and it's below the white two white spots
or off
to to the left of the screen so here we
see the the
how these uh bodies have evolved
over in the case of
these 61 hours and in the case of
39 hours off on the limb
of the planet up at the top of the
screen
we see q the the impact q
just coming around so that from this
point of view you can see that
q has landed now q2
was scheduled to arrive
so that it would have impacted 12
degrees
into the field of view here
if it arrived according to paul chodes
last
computed time arrival it should be the
tiny little
brown spot that you can scarcely see
if you look across from
the q impact site toward the g
impact site there's a small brown comma
in there which is almost invisible
now that's either q2 or that's a culit
q broke up q2 is a younger fragment
than q1 so it's quite possible that
there are other fragments
we have only one orbit of data and we
got this down at two o'clock this
morning so we have been busily
setting this up for you and we haven't
had
any chance to check so one thing we can
say about this feature
is that this is the smallest impact site
we have seen yet
and certainly when you consider that
the fact that it is brown is interesting
now can i have the other graphic please
describe which one it is you're looking
for okay this one
okay now this one is that taken at about
the same time
in the methane filter
so that every place on this that is dark
is dark because the the sunlight is
coming in and the methane gas is
absorbing it before it can get back
out now look for
our little friend in that
you see the q site on the on the edge of
the planet there
that may be a complex of q2 and q1
or that may be q1 and then down
along the track you see a tiny white
spot
now in the in the insert you you see a
grossly
filtered view and you see
the pattern of the evolving
g site and you see that the q
site at the top and in between you see a
little white
spot now this is much
much fainter than the d-spot was
when it was young it was quite easy to
see it in methane light
so this definitely is our baby
of the whole family and what's
interesting is that
in the images that i put together to
make the color view for you
it had the same color dependence as any
of the big spots
it too is dark in all of those colors so
whether it's q2 or not
is really not that significant what's
really significant
is that this tiny little one went in
and it's behaving in the same it has the
same
color behavior enough material came
up to get high enough above the clouds
to reflect and be white
and still in all the other colors
it's dark so that may we now are
sort of getting a lever on this and this
this may help us to argue whether this
material is really coming from a comet
or not
now we have a problem uh about the the
17th of may hal took an image that
he had and he assumed that the
brightness
of the comet was equivalent to the mass
and from that he computed the energies
of impact
and if you set the impact energy of a
equal to
one the impact energy
of d was equal to one and the impact
energy of g
was equal to twenty four now he had
predicted that the
impact energy of q would be 25
and the impact of q1 would be 25 and the
impact of q2
would be 10. l was 15 so
l is in line but if this is q2 it's
really
out of line but i was astounded when i
saw the impact of a
because i was waiting for g which was
going to give me a reasonable
impact so here we're finding out that
the assumption he made is proving not to
be true
now it was the only one he could make at
that time to get some sort of a handle
on it we did a lot of our scheduling
around it but
at that time hal warned us that there
might be a different
problem involved here as well it turns
out that a
f and q 2
are not on the same line as all of the
other
comet hits so the result is that
they have been ejected in the breakup
i'm sorry it's d f and q
two they have been ejected in the
breakup and howell warned us that they
might
not be like the others they might not be
as consolidated they might be composed
of
a spray of particles that have been
ejected and so far hal
has got a smile on his face because all
of the ones that were
out of line are if this is q2
he's he's got a you know straight run
here
batting 400 on his small particles that
are out of line
i'd say he's batting a thousand wouldn't
you really
we haven't we haven't gotten them all
yet
but that really i just just to
encapsulate what you said
uh what that's really supporting is that
the guys that are in line which seemed
to be initial fragments from the breakup
of the comet
when it got closest to jupiter uh are
more or less
compact objects and are behaving like we
would expect from the photometry
whereas these guys that are off the line
are more likely swarms
and and so we get greatly fooled by the
brightness then
as to what's really there but this also
means that we have two kinds of probes
yep doesn't
that's great okay uh
let's go on here now to uh to david levy
uh for an update on what the amateurs
are seeing
yeah there's quite a bit to say um
there is there are a lot of
continuing reports of of
very large dark spots visible at the
impact sites particularly k
l and g parading across the disc
a report from england saying that they
are more spectacular than ever
very large and dark and reports from
everywhere indicating that they are
about as big as the great red spot uh
they are as dense as a satellite shadow
and for those of us who have looked who
have a lot of have some experience
looking at jupiter
uh this as a satellite
parades across jupiter's disk it
uh it transits the disk and you can see
a very dark shadow
across jupiter and this takes
a couple of hours as especially the uh
the moon io
transits and there these are benchmarks
when when you see a satellite shadow it
usually is the easiest thing to see
on the planet and here we have dark
spots that are not satellite shadows
they are every bit
as easy to see as the satellite shadows
but they appear to be as large as the
great red spot at least the large impact
sites
are as large as the great red spot this
means
that these are the most obvious features
ever seen on the planet jupiter
this also means that just about anybody
can go out and look at these
and as i mentioned yesterday i recommend
that people
in people that don't have a lot of
experience looking at jupiter
should still not pass up this
opportunity to get acquainted with this
beautiful planet
uh go to your planetarium if they're
having a star party or amateur astronomy
club
and get someone to show you this
beautiful beautiful sight
and if if i can stop
going to these dinners and stuff that
we're having i'd love to see this
myself but whenever it clears up in
washington i'm told that i have to eat
something
but wait until you get to tucson the
weather the seeing is much better in
tuesday i know i can't wait to do that
there is there is some interesting news
though
for what's in the future tonight the
final two fragments which is really is
kind of sad to say but the final two
fragments are going in
and v and w uh v comes in around 12 15
or so
eastern daylight time which means that
for us uh v is jupiter is going to be
set and we won't be able to see anything
on the east coast of the united states
for people on the west coast though
jupiter will be just dandy just
sitting there beautiful evening sky
there is and and i want to caution that
this is very unlikely
but if there is any chance for visual
observers experienced
visual observers to see the in
the flashes of the impacts either the
incoming
meteor as the uh as the fragment
starts going in to the stratosphere or
the explosive plume that we call the
fireball that comes afterwards and lasts
quite a bit longer
the best chances come tonight with
fragments v
and much later w w will be easiest to
see for observers in
california jupiter will be low there but
hawaii
the south pacific and observers in
australia and new zealand
should have a good chance w is a pretty
good fragment
it's it's pretty fair size it's a nice
one to end our
end our party with and also
is the one that is hitting closest i
think
to the limb of jupiter to the edge of
jupiter
so what's happening tonight is we can go
out and look at the dark spots
and also if we're in the right position
to try to see
if we can see any flashes indicating the
final impacts
thanks david lucy can you
bring us up to date on the on the latest
impacts fragment are impacted about
several
hours ago and what where are we standing
sure i'll try to there's a lot going on
so it's a challenge to keep up with
what's happening
uh fragment r impacted several hours ago
and we have this report
from david schleicher at the lowell
observatory in flagstaff arizona
accompanying this i'll keep talking
until we get the image up
we have also confirmations from mcdonald
observatory oh here let's listen to
schleicher's report
it appears that if we are detecting a
plume from
the impact of our this is using methane
filter
8900 angstroms we're somewhat surprised
that
being able to see it at all because
there have i don't recall
there being that many detections of
plumes in the visible
most of them have been in the infrared
so far it may mean that it was a bigger
piece than
some people have been anticipating
well um i think dave was uh suffering
from a
astronomer's fatigue um because other
there have been a number of reports um
mcdonald observatory was looking in in
the same methane band
and they did see a bright uh bright uh
emission in that in that spectral region
uh the keck observatory als
also reported inca de peder from ucla
and her team
reported seeing a truly remarkable flash
from the impact of r
that lasted for about 20 seconds and
then the plume the hot rising gases
appeared eight minutes later over the
limb
and brightened and then faded over a
period of about eight minutes
now we have a report from the galileo
spacecraft
and as you recall this is really a
significant
significant return because galileo's
looking directly down on the impact
sites and they actually can see when the
initial explosion
occurs we have terry martin reporting
today we were pleasantly surprised to
pick up event
l which was originally not expected to
be captured because of the timing
relative to the predictions of impact
but
the actual impact occurred later and we
picked it up
and this one is actually brighter than h
by
almost a factor of two it's more like uh
five to six percent the brightness of
jupiter
and it takes 35 seconds or so for the
light to die back down again
so we see we think that we are seeing
the
actual meteor flash the transition of
the
fragment through the atmosphere and the
very hot
emission from that but over a very small
streak of light across jupiter
and this is a short duration and
precedes
the the plumes and the fireballs that
are being seen
from other observatories
let's hold that up if we can can we
bring that back because i need to
address the inset in there
if possible what you are seeing is a
tracing
of intensity as a function of time and
if you can recall the inset and we'll
review it again later
time goes proceeds along the bottom axis
the horizontal axis and the flash is
represented by a
drastic a quick increase in intensity
and then it decays
as time goes on um then
let's see we're sort of working
backwards in the alphabet of impacts now
um report with some reports that are
coming in we have the european southern
observatory
um showing the k-impact fireball um and
showing the plume and i think we'll just
put that up briefly
um okay yes we'll
here we have the residual from the g
impact and
the quite prominent h impact now many
most
i i would say all observatories are
reporting um that there's
detectors that they're over exposing
their images
even when the first reports came in and
reported over exposing or saturation of
their ima
of their detectors i'm sure everybody
reduced their exposure times yet they're
continuing to be over exposed so
again we're we just continue to be
surprised at how bright these
these impacts are um we have a movie
from
from the sac peak observatory which is a
solar observatory in new mexico
and we will run that i haven't seen this
this is of the g
fragment impact and it's a time
time series
i'm sorry sacramento peak i i used the
abbreviation it's the national solar
observatory
so we can see jupiter rotating with time
and the these data will be analyzed in
terms of changes in the brightness and
and any spatial variation which can be
determined and we will of course
correlate these results in the infrared
with the um
visible and ultraviolet images that are
acquired from the other ground-based
observatories and the hubble space
telescope
now we have our first report from
another
earth orbiting satellite the extreme
ultraviolet explorer
and we have we have a video of that
and a voice in oh no voice report first
has not really
uh changed that much yet which may or
may not be a surprise since
it'll take a little while for this stuff
to reach the taurus
but one thing we have seen is that the
if we look at jupiter alone in the
extreme ultraviolet we actually see
signs of helium emission during the
impacts
that we don't see before the plumes did
go up fairly high
because we have to have thrown helium
far up in the atmosphere to be able to
see this several hundred kilometers
in order to see see this emission
through all the hydrogen that absorbs
the at these wavelengths
okay we're showing there um first of all
two things one was a bright emission
band from from helium seen in jupiter's
atmosphere
and then they're also reporting about
the uh the taurus around io the moon of
of jupiter which has which is a ring of
charged particles and they're reporting
that they have not seen any changes in
the
density of of charged particles around
io so that's a preliminary negative
result
and finally we have images from
australia from the siding spring
observatory showing the c and g impacts
when it says speak from my notes
well
i'm not prepared to speak to this but
these are
nice images and i haven't i haven't done
my homework
so i'm sorry australia but these are the
c and g impacts
at different wavelengths which my guess
is which is looking at different
uh levels into the atmosphere the first
one looked like a methane band image
don't you think lucy yeah we've got
three wavelengths
and i'm sorry we're just gonna have to
pass on that one
okay uh maybe this is the time for us to
turn it back over to you don
okay we'll have a question to answer but
first i want uh to make
an important uh announcement on our
schedule for tomorrow that's a friday
briefing
has been changed to 2 p.m eastern time
we will not have an 8 o'clock in the
morning briefing this is to
to give the science team a time to
prepare
the information and images on the
one-two punch of q r
so we'll have that tomorrow at two and
uh and then as a preview for saturday
we're going to also change the time to
11 o'clock
am eastern time and on that one we
expect to
have evidence for sonic boom on jupiter
observed and we'll
also look at what is expected to be a
dramatic plume from fragment w's impact
and look at changes we're already seeing
on the impact sites
i'd like to open it up q a from goddard
first
please wait for the microphone state
your name and affiliation please
uh paul hoverstein usa today a question
i guess for
gene and david uh weeks ago
uh there was so much emphasis put on uh
we may see nothing uh let's be cautious
and so on
i'm wondering if if you can say now that
that was a matter of
maybe overestimating the resiliency of
jupiter or was it
underestimating the magnitude of these
fragments or some combination
we're being criticized because it's been
too good
i'd say the the thing that uh caused the
most uncertainty
prior to the actual beginning of the
impacts was the whole issue
how big are these fragments how much
stuff is there
now we had two estimates independent
estimates
that suggested that the original
precursor body was of order
10 kilometers across and the big biggest
fragments might be in the ballpark of
about three kilometers
or an upper bound that was given by hal
weaver
from earlier hubble photometry was about
four kilometers for the very biggest
that would have been
well that time was q that was that
seemed to be the brightest
now the issue was are we really seeing
the nuclei
or maybe the nuclear completely shrouded
in dust
so hal weaver and his team were trying
to do this job
tried to do the best job they could to
subtract off
the dust effect to see what's left
what's there in the middle
but you could argue that maybe that we
weren't actually seeing anything else
but dust and that the nuclei could be
much smaller
we're defeated by physics right
basically it's a very difficult
observation
uh the other team that was proposing
that these objects were big
consisted of the dynamicist team
at jpl paul chodes and don yeomans and
zdenek sekinina and they said if they
try to do their
best fit to the to the actual
orientation of the string of pearls
that they found a breakup of the comet
initially
about an hour and a half after it passed
perijove
and they get from that com just that
dynamical solution
they gave a size for you can get the
size of the original object because
where the things go in the string of
pearls depends on where they are
relative to jupiter at the time of
breakup so that's how you get the number
uh and it turns out their result agreed
very nicely
with with the weaver team and we were we
were very happy about that but now there
were other solutions
on jay milage and jim scotty for for
example that assume the breakup happens
right
at perijove then the original parrot
body is much smaller
and so you know we so that's that's
where some of the confusion was
occurring it turns out that solution is
very sensitive
to just exactly when the breakup occurs
now the other thing that that had come
out very recently
particularly work by willie benz and
ashfog
i suggested that really the comet was
just a pile of debris to begin with and
you could account
for the string of 20 pearls quite nicely
if you just smashed the whole thing the
whole thing just came apart
but then it gravitationally
re-aggregated by its own self-gravity
into little clumps or knots
and if the and actually there's a
there's a lot of power behind that
argument
i think that we've got to address that
argument because we i think that looks
like a very strong argument
so the question was are those clumps
spread out in which case
they may appear brighter and there may
not be as much mass
or the clump did the clumps get back
together again so something like g
or h hitting jupiter is really
bound together grav by its own gravity
and would come in maybe get
slightly separated as it enters the
atmosphere but effectively act like one
projectile when it hits
or what is just going to be pulled out
in a long string
and as paul weissman said sort of hit
jupiter like a string of machine gun
bullets
and that was the source of the idea of
the great fizzle
it looks as though jupiter is telling us
in my view at least
that that you had pretty good clumps for
the guys that are on the line that's
just what we were talking about today
so they're the ones that got back
together and made pretty good clumps and
the ones that are off the line are the
more diffused swarms
that's been a guess and it looks as
though what we're really seeing on
jupiter
supports that yes
uh bill hartwick cbs and just to follow
up on that was part of the question i
wanted to ask the the mechanism for
the ones on the line and then the later
break-offs where you have these off the
line
i'm interpreting what you just said that
it was all clumps to start with some got
together and made big clumps
and some never managed to do that is
that what you're saying the mechanism of
it and the second question was
in the g impact site where there was
that sharply defined ring that
we said we're going to look later and
see if it was expanding has anybody
looked and is it
do you know what that is yet let's take
the first part and then
i think i want to throw the second part
to some others here uh
the first part is that some of the
things that are off the line
demonstrably split off from other clumps
late late in the history of the comet uh
because
we we essentially almost caught them in
the act of separating
with the images taken last july with
hubble
q1 and q2 are just starting to come
apart and p1 and p2
were actually not very far separated so
it's clear that those things began to
separate
even after the event and those things
that separated late
in part seem to be the things that have
drifted off and maybe mostly swarms
yeah the q fragment actually uh there's
evidence that fragment q was
starting to split up at the time of
discovery of the comet
and that the date of around april first
93 for
breakup of fragment queue might be
making p
probably at that time q and p being
formed that way i was just going to say
that i have a slight modification to
what
you know gene was saying my picture of
what's going on of you know
for these fragments that are off the
train is that in fact
there still are you know single large
bodies at the centers of each of those
things
they're anomalously bright because they
have more dust the younger object
the younger the object is the more dust
it has we see that even for the main
fragments
the amount of small dust gets blown away
eventually by the solar radiation
pressure
and is removed from the system that
makes the comet appear
fainter because what you're observing
for the most part is this dust
and if you have a younger object you
know if you compare
the brightness of that object to
something that's on the train you're
comparing them essentially at different
times in the in their dust production
and so uh using the brightness is
is uh basically misleading you
as an indicator of the size because
there's more dust associated with these
things off the train
than the ones on the train and
but i think that for example when you
look at the
this interesting q region as gene was
mentioning in at the end of march
you actually see one of those small ones
the so-called p2
break up almost before our eyes into two
separate
you know condensations essentially i
don't believe that that could be
explained by a
swarm model it's hard to make it's hard
to believe that it's more naturally
explained it seems to me
as having a single object there that is
now very fragile i mean we know these
things are extremely fragile
and then it just broke off again and
that's why i was so interested in this q
region
watching it prior to its impact into
jupiter thinking that
wow this this region most of these
fragments have already shown evidence
that they're extremely weak maybe even
weaker than the others
and we might see these things coming
apart but up until 10 hours prior to
impact we
didn't really see any evidence that q1
and q2 were
splitting into you know just a swarm
can we answer the question about the
ring read it could you
i'd like to ask to defer that until
tomorrow
andrew ingersoll is back at the
institute beavering away
trying to get this all put together for
you this is a part of his sonic
uh boom scenario so i think we'll just
kind of hold that and
let him work it out for you come on
there's a hint if he's saying it's a
sonic sonic boom you
you know it's got to be expanding
uh it's alan merson from national
geographic magazine um i guess this
question is for hal or gene
you mentioned that fragment m had
disappeared for a couple of weeks
and then reappeared at impact and i and
you talked about the fact that this
fragment turned on and turned off
and i wonder if you could describe what
exactly that means and how that works
uh fragment m was only seen seen uh
last year okay uh all of this year
nobody has seen m and i think what
happened there was that small dust
uh basically got blown out of the system
leaving something that was a pretty
small object but still could be
substantial
and that's and the the fact that you see
evidence
for the impact on jupiter indicates to
me
that you still had something fairly
substantial there maybe on the order of
500 meters
something like that something that was
below the detection limit of all the
telescopes that are looking for example
hubble
really wouldn't have been able to see
something that's smaller than about 500
meters in size
even if it had no dust cloud around it
and so uh
that's what we're seeing i should say
that this is kind of a classical problem
in observing comets
many comets have been observed to
essentially turn off
and disappear and we've always wondered
what the two hypotheses were did these
just
break up and dissipate or did they
simply shut down
they stopped being active and therefore
the all you have is the bear nucleus
and it's too faint to see and of course
i think hal and i are very much on the
same side of this this issue
and that's why it's so delightful to see
there really was something left
when when fragment in hit because it's
been gone for a long time as hal said
so the dust was gone but there was still
a body there and it came on in
and made an impact a question
third row
uh jim reston for esquire um
dr bibi i'm still very confused about
this water
issue and the absence of of the
observation of water
can you explain just historically how
astronomers in the past decades deduced
that there was a band of water 50 to 100
kilometers deep into jupiter's
atmosphere
and that now when you're not seeing it
obviously
after all of these impacts does that not
suggest that there are
four options here one that there is no
water there
or secondly that uh these things are
exploding
higher in the atmosphere and not going
deep in
or that the impactors themselves are
much smaller
and therefore disintegrating before it
reaches the 50 to 100 kilometer
range or lastly that the black clouds
are masking the material that is ejected
the
the water that may be ejected and that
the black clouds is commentary material
which of those theories are well say yes
to the first three
okay would you would you take it first
how how it was deduced before we had
this experience
right don't blame the astronomers for
this
blame the chemist
basically if you assume that jupiter was
made out of the same
thing that the sun was and you
do the the chemistry
you realize that when you're going
into the planet when you reach certain
temperature the ammonia ice will freeze
out
and if you go below that the ammonia ice
will be gaseous
but as you continue down doing doing
your equilibrium chemistry study your
balanced chemistry studies
you get to another layer where if there
is
hydrogen disulfide and ammonia there
they will combine and make a new kind of
ice
and finally as you go deeper and deeper
into this planet that actually
sends up 165 percent more energy than it
absorbs from the sun
to get down to those deeper temperatures
you finally get down there to where
the temperature is about zero degrees
centigrade
and then you're going to have water if
there's any oxygen
because you've got hydrogen all the way
through now
an obvious reason that we are not seeing
this water is we didn't get down to it
and that's an easy one but we then must
look very carefully at all the spectra
get identify
all of the molecules and try to get a
self-consistent idea and again
the chemists are going to come back and
take over in the final
analysis and tell us whether we're right
that's
one of the very nice things about
studying planetary science we have
enough
different types of data that
the astronomer goes out and gets it and
then the chemist and the meteorologist
and everybody else tells us we're wrong
and starts working on new models that
improve it
so at this point in time i tend to favor
that we
didn't reach the water level but that
water
level is sort of a nebulous little thing
it ought to be there but we really have
never got a good sounding of it
so i just to encapsulate it is the
historical view that there is a band of
water
50 to 100 yes is that in jeopardy
that theory no i don't think so
unless when we've worked this out we
decide that they had to penetrate that
deep
then we'll have to raise that question
and if that's the case then in december
of 95
the galileo probe goes in and we get
another crack at answering it
miles and we'll come back to this side
miles o'brien with cnn and this would be
for anybody who wants to take it there's
a report out
of australia this morning that observers
there actually saw
a flash in the ring of jupiter uh
question is
are you surprised that we haven't seen
more of these observations before
and what did you hope to learn from the
flash sightings indirectly in the first
place
well for one should remember seeing the
ring of jupiter is a bit of a feat
in itself it was of course discovered
with voyager 1
and only later was it actually seen from
telescopes on the ground
mostly you need a pretty big telescope
and
the best trick is to look uh in an in an
ammonia ban
excuse me a methane band so that you can
reduce the light of jupiter
but where the ring might be bright that
was being observed i should say a
palomar observatory with a 200 inch
telescope
the anglo-australian telescope is
another good one to do this experiment
but it's difficult what one really hopes
to see
since the ring is in close however it's
really faint
the ring is in close if you can capture
the flash of the initial entry meteor
that was one way we could
by observations on the ground determine
the actual moment
of entry into the atmosphere that those
first few seconds
as the meteor is just plunging in the
upper atmosphere we're hoping i should
get a timing on that of course it gets
them very bright as it approaches the
ammonia clouds
so being a that times the actual impact
for us and that's an important thing to
do
it's a delight we heard this morning
that they're actually seeing those
flashes now
and picking them up i think that's very
important
that people thought you might see
flashes and it was also some of the
satellites and i might be mistaken but i
don't think i've heard many reports of
flashes being observable in the
satellites right i can
i can speak to that miles um there have
i have
four negative reports of
uh the absence of flashes observed off
as reflected off of the satellites of
jupiter so
the people have looked for
everything was that yes
um people people have looked for
evidence of flashes off of the galilean
satellites
the reflection from the flash as it
impacts jupiter
they have reported not seeing that so um
that has that has not happened and and
i'd like to talk to you later about
seeing flashes off the rings because
they were trying they were looking for
that and
you're ahead of your of reading the
candidate was k because
europa was in shadow those observations
were going to be made
mostly in australia uh could have been
made in hawaii that's the region
and i haven't heard they were made and
they reported negative
not seeing anything there is one
probable observation of a flash
from uh israel of a flash reflected on
europa
uh one of the satellites it is a 0.06
magnitude uh six hundredths of a
magnitude
increase right yeah it's listed as a
probable though not a definite
rita you had something you wanted to add
to this a second reason for wanting to
see the fireball is that you know
how far the ring is from the surface of
jupiter and if you can measure the
increase of brightness
off of that ring surface and
you have a little an idea of the
particle density in that ring from the
voyager data how thick the stuff is then
you would have a measure of the fireball
itself we haven't been seeing the
fireball
and had you gotten a sequence of these
even though you didn't understand the
ring
the difference in brightness would give
you
this relative strengths of the fireballs
when rita says fireball now she's
meaning what's traditionally used as
fireball for a very bright meteor
that's right rather rather than the
fireball we've been using it here in
this group
as as something formed deep in the
atmosphere performing the plume i just
wanted to clarify that
yes this would be the initial flush
which would be very closely related to
the amount of energy that was going in
it hasn't really even interacted with
the atmosphere yet so it would be very
fascinating to get a whole series of
these flashes and then just
well that one had the most energy and
right well galileo's doing
galileo is doing that the
photopolarimeter radiometer on galileo
will have that information we're going
to have time for about one more
question here and then we have to go to
headquarters and
we'll we'll have more time after the
satellite goes
uh david chandler from the boston globe
for dr bibi
um two questions um on the uh
uh latest color image of the g
impact site um how do you interpret that
uh apparent sort of brownish color that
we're seeing there
or can we learn anything from that
coloring and secondly
um comparing the initial
photos of the g impact site and the most
recent ones
what can you say about the evolution of
that impact site
well first of all this large feature
we're seeing
has to be high on the atmosphere because
looking at the different the image in
different colors
you can literally see the east-west
cloud patterns to the north of it just
pass
right through this structure i mean
this was an olympic ten dive when it
went in it didn't splash the atmosphere
the atmosphere
underneath looks very undisturbed
just passed right on through and what
came back out must have come right back
out the chimney that the in-going
particle
developed so what you've seen see now as
you see this
huge umbrella of material
above the site now the reason i'm on
this team is that i wanted to see a
bubble come up
out of that site and interact with the
winds and
uh i would then understand how much
energy it had taken for all the storms
i've been watching for the last 25
years but so far my bubble hasn't come
up and my bubble may be under that brown
material but if that brown
material were down on in the
ammonia cloud deck it would be stringing
out
it would be headed north along it would
be headed east along the north side of
the spot
and it would be headed west along the
south side of the spot so you just see
the things starting to
run out as abandoned street we don't see
that
so that it's still decoupled from the
tropospheric winds
and we expect those winds to drop off
with height in the atmosphere when you
get up to a certain point you wouldn't
expect
it to be sheared out so that that's
another limiting
piece of observation that says this
stuff is definitely high
to me that it's probably twofold it's
probably particle formation which really
obscures
things and those particles are dark
we'll take questions from headquarters
now please state your name and
affiliation
this is dick kerf science magazine
have there been any attempted
observations of
the impact of fragment j and if so what
were the results
i don't recall hearing anything anyone
else
that was one of the other missing nuclei
the thing that this one of the ones that
disappeared that was seen early
in the spring i guess last year in fact
that disappeared even before
uh before july of last year i believe
so that was you know that must have been
a really small one no no reports of that
i wouldn't be surprised if we look back
in our data and uh
find it
david miller u.s news and world report
do we know the size of the diameter of
the so-called fireball from the impact
of g
well i think we do have a pretty good
measure we saw
uh g uh well enough and
actually um one could compare it
with the with a whole series of uh
images that we saw on the limb from a
and from e that the initial fireball
would probably grow to a diameter
of about
8 000 kilometers before it starts to
collapse
and then as it flattens back out again
uh it easily gets uh about twice as big
does that answer the question
okay we're coming back to goddard now uh
mark
this is mark crow of the houston
chronicle could you go over again
about when m hit and who saw it who
reported
who gets credit for that and how does
that change the
the total of of known impacts
that you think will happen and is it
possible that there are some other
fragments that have turned off and on
and that may have hit
and and will you go back somehow and try
to figure that out
okay um yeah this the reports of
observations of fragment m were made by
imka depayder
at the keck telescope on mauna kea
um and when she saw it she wasn't sure
if uh
you know she observed a flash but she
wasn't sure what was going on i mean so
she even didn't say anything about it
about it for a day
but then had a co i i talked to her on
the phone and she
we our interactions convinced her that
she had probably was probably detecting
it
now it's going to take us time i mean
this is the type of
thing that's going to make us go back
and look in our data for other
you know other small signals or
relatively small
signals in this case and and you know
do some quantitative calculations and i
think it's possible we'll
uh you know find more of these now i'm
not sure if i answered your question
yeah sorry i just wondered how this
changed the fragment
count now for the whole for the whole
training
count well boy i'm so confused that
counting is getting difficult
um i mean i would say okay we're saying
they're 21
and so that boy i don't even know if m
was included in our 21 count
too tough a question m and j were parts
of the original count of 21
uh as as designated from the mauna kea
observations by david
jewett and jane liu since that time
m and j had disappeared but more
fragments at four
so q split
uh into two fragments p split into two
fragments
mean times p2 disappeared or became a
puff
uh in addition there was a fragment that
split off of
g g and rather more recently
this reminds me of the games my dad used
to play with me at dinner time and
doing sequence of arithmetic
where are we now if there's something
left from all of these splittings
then we've got a total count that's
greater than 21.
possibly i can i can think of at least
four more or three more that you would
add to that count
now where they're all still there that's
comes out of the issue is there
something
left when the when that thing disappears
but you talk about 24 that we might hope
to see yeah and also just
um don't don't turn off the set quite
yet after tomorrow
uh the the trailing wing is going to
continue to impact jupiter these are
small small particles
a wing of dust mostly it's mostly a wing
of dust really tiny particles uh dust
sand grain size maybe even smaller
but we don't know what the real sources
of the dust were maybe they're boulders
yes they they may be larger but the the
interesting thing is that
the impact sites as you can see from the
site
of v w tomorrow much closer to the
limb of jupiter
closely available for the next few weeks
they're expected to be most common
the most active uh between
the end of the impacts tomorrow and
the end of september i think and they're
going to be progressively moving on to
the side that we see so the number of
fragments
if you count all these little guys
coming in could go up quite
substantially
we have time for one more here okay
i have questions on dr river uh i want
to ask about the
remaining or the bureau of dust you know
will that cause the
material shower you know every year to
jupiter or the
will it uh tighten the jupiter sling
or what happened to the fall dust yeah
there is a substantial amount of dust
that actually misses jupiter
it stays in orbit around jupiter uh gene
i'll have to defer to you as to what's
what's the ultimate fate of that dust
well uh there's a
an astrophysicist at the university of
colorado boulder by the name of haranye
who's done a very careful study of what
happens to the
dust that's in the tail which which will
all the collective tails which will stay
in orbit around jupiter
and his analysis indicates when you take
account of all the forces
acting on these particles which includes
magnetic forces because these will
become
charged as as well as the more
conventional
forces that we're used to thinking of i
don't want to give all these are
pointing robertson effect and there's
direct solar radiation pressure and so
on uh
his analysis indicates that this dust
will gradually settle down
into more or less circular orbits and
form a very diffuse
kind of tall ring outside of the present
ring
of jupiter now whether there will be
enough dust there for
anyone to see anything that's another
question
but at least that's that's where it's
predicted to go
okay uh we we're going to have to uh
stop at that
for right now and have time to uh and
let you remind you again about the
briefing changes tomorrow at 2 p.m
and saturday at 11 a.m eastern time we
will clean feed
the video and if i could also ask for
just a moment here and
introduce from nasa headquarters the
nasa chief scientist
dr france cordova
thank you on behalf of the nasa
administrator
i'd like to congratulate all the
participants in this event
for the inspiration that they continue
to give and for their hard work and
dedication
who of us can never forget the faces of
the young observers as they saw the data
come across this computer screen for the
first time i know i'm not going to
forget the face of heidi hamill and my
own intense suspense as i saw
roger yell keeping us back from finding
out exactly what
was uh that element in the ultraviolet
spectrum of the g
impact site astronomy is about
transforming images those images that
turn
upside down our world view and that give
us a new perspective on ourselves and on
nature
what we see here this week is the
culmination of nearly a year of intense
preparation
our goal of providing information and
data in a timely fashion
is being accomplished and with the
continued participation of these various
individuals
we will continue to bring news of this
comment
through saturday i understand there's
five uh pieces of the comet left to go
and in the next few months we'll be
observing the after effects of the
comet's impacts
expecting to gain new and unprecedented
insight
into the origin and evolution of the
solar system
i think in particular eugene and carolyn
shoemaker and david levy
the discoverers of the comet for their
efforts over the last week
to discuss not only the unique
scientific
values of these impacts but to express
the excitement of science
they're an inspiration to all of us and
i thank the young observer scientists
because they touch the future of lifting
the imaginations and fueling the
aspirations of young people all around
the world
the observations of this comet
constitute one of the best examples of
inner cooperation
between agencies also and we have a very
fruitful collaboration with the national
science foundation and nasa
in uh supporting uh many of these
observations
most professional observatories as
you've heard around the world are
observing the comet
and in addition observers all over the
world are using the computer electronic
bulletin board maintained at the
university
of maryland that lucy mcfadden has so
eloquently spoken to this week
networking specialists and computer
experts around the world
are playing an important role in making
this data easily available and very
quickly to to interested people
everywhere ground crews i'd like to
thank
for the spacecraft like the hubble
galileo ulysses
the international ultraviolet explorer
voyager and the extreme ultraviolet
explorer in the kaiperin airborne
observatory because they've been
preparing for the
these observations for many months we
anticipate their results with a great
sense of expectation
and finally i'd like to thank the staffs
of the goddard space flight center and
the space telescope science institute
for taking the lead and pulling together
in one place all the right people to
make sure what's happening
is available to the broader public and
the professional staffs of these
organizations
on behalf of mr golden i commend them
and their colleagues around the world
for their highly successful efforts
and on behalf of myself who am an
astronomer i thank you all for your
affirmation that science is fun
if not quite as simple as abg
we'll see everyone again tomorrow
morning and
two excuse me tomorrow afternoon at two
and again saturday at 11 and
we'll have the clean feed coming on now
for uh for here and down the line thank
you
today we were pleasantly surprised to
pick up event
ill which was originally not expected to
be captured because of the timing
relative to the predictions of impact
but
the actual impact occurred later and we
picked it up
and this one is actually brighter than h
by
almost a factor of two it's more like uh
five to six percent the brightness of
jupiter
and it takes 35 seconds or so for the
light to die back down again
so we see we think that we are seeing
the
actual meteor flash the transition
of the fragment through the atmosphere
and the very hot
emission from that but over a very small
streak of light across jupiter
and this is a short duration and
precedes
the the plumes and the fireballs that
are being seen
from other observatories
it appears that the taurus has not
really
changed that much yet which may or may
not be a surprise since
it'll take a little while for this stuff
to reach the taurus
but one thing we have seen is that the
if we look at jupiter alone in the
extreme ultraviolet we actually see
signs of helium emission
during the impacts that we don't see
before the plumes
did go up fairly high because we have to
have thrown helium uh
far up in the atmosphere to be able to
see this several hundred kilometers
uh in order to see uh uh
see this emission uh through all the
hydrogen that absorbs the
at these wavelengths
by detecting a plume from the impact of
our
this is using methane filter 8900
angstroms
we're somewhat surprised at being able
to see it at all because there have
i don't recall there being that many
detections of plumes
in the visible most of them have been in
the infrared so far
it may mean that it was a bigger piece
than
some people have been anticipating
you