From the moment the NASA briefing begins, it becomes clear
that this comet crash will be anything but uneventful. The Hubble Space
Telescope pictures from the first comet fragment impact are nothing short of
spectacular -- and Fragment A was one of the smaller fragments! Thus begins a weeklong
television drama played out on the NASA Channel, in which scientific progress
-- with all of its discoveries and delays and debates -- will unfold on a daily
basis for all the world to see.
Dr. Heidi Hammel, the Hubble Space Telescope's team leader, begins by discussing an image from the Hubble that is displayed on our screen. It
was taken with the telescope's Wide Field Planetary Camera using a blue filter.
Jupiter appears as a big gray ball. But something dark is visible in the lower
left-hand region -- something that wasn't there yesterday. An enlargement shows
the dark object to be a black spot partially surrounded by some lighter-colored
smudges. This is the impact site of Fragment A, Heidi explains.
According to Heidi, most of the images received thus far
look similar to the one shown, with dark impact features on a light background.
The exception is in the methane band, where the image is reversed and the
impact features look bright.
Later in the briefing we learn that those dark markings in
the impact region are a surprise to scientists. New features on celestial
bodies such as Jupiter are typically bright instead of dark.
The width of the enlarged box is "about two Earth
diameters," Heidi states to my surprise, adding, "so that structure
that you're seeing -- that circular pattern -- is about the size of the Earth!"
The image with the black spot is from the second sweep of
Hubble across Jupiter. Since the Hubble spacecraft orbits the Earth, it cannot
image Jupiter during that half of its orbit when the Earth is blocking its view
of the planet. During the first sweep, the Hubble telescope obtained images of
a bright "plume" that rose some 1,000 kilometers (621 miles) above
the edge of Jupiter after the first impact and then flattened. (A kilometer is
about 0.62137 miles, roughly 5/8 of a mile.) Those images are not available for
release yet, but Heidi says they should be ready tomorrow morning.
Heidi uses a grapefruit-sized globe and a marking pen to
demonstrate the geometry of the comet collisions with Jupiter from the Earth's
vantage point. The globe represents Jupiter, and the pen represents the train
of comet fragments. Heidi holds the globe in one hand and gestures with the pen
in her other hand, pointing it upward at the Jupiter globe and approaching it
from behind at a shallow angle. The comet fragments, she explains, will be
approaching Jupiter's South Pole at an angle and hitting on the far side that
we cannot see.
However, due to Jupiter's rapid rotation, each comet
fragment crash site will come into view shortly after impact, allowing Earth-based
observers and telescopes to see the effects of those impacts within five or ten
minutes.
A video is presented in which a colorful Jupiter spins on
its axis. This is a composite of five high-resolution images taken from the
Hubble Space Telescope. A computer enhancement was used to knit the images
together and project them onto a sphere. Heidi apologizes that the image is
rougher than it could be. It was created by Eric de Young from data received
just 18 hours ago, so they haven't had time to clean it up yet. The planet is
divided into segments, like an orange. At each division, a diffuse vertical
line with bluish overtones is seen.
The spinning Jupiter image shows the planet's appearance
before the comet impacts. Heidi proudly points out that the image demonstrates
the "amazing quality of the images from the Wide Field Camera" of the
Hubble Space Telescope, and I marvel at its detail. The planet has an orange
hue, with bands of lighter and darker color encircling it. I watch for the Great
Red Spot to appear, that famous storm on Jupiter. In this color image, it is
readily identifiable as it slowly spins past, appearing as a large, orange-tan,
squashed oval just below the equator.
The dramatic image of the Fragment A impact site is
displayed again, and Heidi makes no attempt to conceal her excitement: "It's
a new feature on Jupiter," she smiles. "And we're going
to have twenty more of them ... even brighter ... "
"It's going to be a great week!"
The NASA briefing is being broadcast live from the Space
Telescope Science Institute (STSI) in Baltimore. Moderator Don Savage of the
NASA Public Affairs Office introduces the other five panelists on Heidi's team.
Each is a member of at least one or two Hubble Space Telescope camera and
spectrograph teams. Three are affiliated with the Space Telescope Science
Institute: Dr. Hal Weaver, Dr. Keith Noll, and Dr. Melissa McGrath. Seated between
those last two are Dr. John Clark of the University of Michigan and Dr. Bob
West of Jet Propulsion Laboratory.
Dr. Hal Weaver reinforces Heidi's prediction with his own
enthusiastic proclamation. "First of all, I'd just like to say it looks
like this comet was not a dud!" Hal says exuberantly as soon as he has the
floor. "Let it ring out to the rest of the world!" He goes on to say
that there's no evidence from the Hubble Space Telescope to support those
earlier reports that the comet chunks were breaking up.
Hal contends that the height of the plume that was imaged on
the first Hubble sweep provides "very strong evidence" that the
fragments are penetrating deeply into Jupiter's atmosphere. He believes a
broken-up comet fragment would not have been capable of creating such a huge
plume nor penetrating so deeply.
The excitement of the Hubble scientists is vividly demonstrated
in a video that shows them seeing the Fragment A impact site images for the
first time. Imagine the scene. All the team members have done their very best
to carry out this first experiment. They have commanded the Hubble to point in
what they hope will be the right direction, using what they hope
will be the right equipment, based on the best impact timing predictions available...
all on the off chance that there might be something to see, and that they
might get lucky enough to actually capture it. But given the relatively
small size of Fragment A, along with the possibility that it might have already
disintegrated, they are not expecting much.
Now it's time to see the fruits of their labor. A half dozen
faces stare intently at a computer screen that we can't see, because it's
facing away from us. Dr. Heidi Hammel is closest to it; she points at a spot on
the screen that corresponds to the latitude where the fragments should be
hitting. "This is the latitude [where] we're looking for something --
right there," she states. All eyes remain glued to the screen. Then --
"Look!" Heidi breathes. Her voice goes up several
pitches: "Look!!"
Behind her, Dr. Melissa McGrath gasps, "Oh, wow!"
"Oh, my God! Look at that!" Heidi exclaims. Her
excitement and disbelief is mirrored in the shocked expressions on all the
other faces.
As realization dawns, the room erupts into excited shrieks,
cheers, and claps. The commotion dies down, only to resume several seconds
later when another unexpected sight is revealed.
Expressions of amazement abound: "Wow!" "Oh, my
God!" "Did you see it?" "Look at it!" "I don't
believe this!" "Whoa!" "Unbelievable! Wow!"
Jubilation reigns.
Cut to a celebration. Heidi and Melissa together uncork a
bottle of champagne. Heidi takes the first swig and holds out the bottle towards
Melissa. The film stops before we get to see how the rest of this scene plays
out.
I am amazed that they showed it at all. Do they really want
that broadcast on national television? Besides, don't any of those revelers
care about poor 'ol Jupiter? That planet has just experienced a cataclysmic
disturbance the size of our own Earth!
Yet the video has an honesty about it that is altogether
charming. In this age of carefully prerecorded sound bites, it is refreshing to
get an uncensored glimpse of scientists in their less conservative moments,
caught up in the excitement of discovery. Too often, we see only the serious
side of science, when the findings have already been made and dissected, when
the excitement has faded, when the human element has been filtered out. I'm
already beginning to like this NASA Channel for allowing me to observe science-in-the-making.
Next, members of the audience are invited to ask questions. Given
that the Hubble was able to capture signs of the first impact a couple of hours
after it occurred, a reporter asks whether the residue from the comet impacts might
remain visible on Jupiter a lot longer than anticipated. Dr. Bob West
hypothesizes that we might still be seeing residual effects from the comet "a
year from now." That's a far cry from today's earlier predictions that we
might not see anything at all!
Bob Cook from Newsday asks if the comet fragment
might have penetrated into the water clouds that scientists believe exist deep
in Jupiter's atmosphere. Dr. Keith Noll responds that evidence of the water
clouds is something that they will be "looking for very keenly."
"If we see a huge increase in the amount of water, more
than could have come from the comet itself," says Keith, "we'll know
something about the energy of the impactor and how deeply it penetrated into the
atmosphere."
Keith says that scientists also hope the comet fragments
will penetrate deeply enough into Jupiter's atmosphere to "churn up"
chemicals and "possibly allow us to see molecules that until now have been
too deep in Jupiter's atmosphere for us to sense remotely."
An unidentified reporter voices the question that is
foremost in my mind: "In the past few weeks, we've been told that amateur
astronomers have little chance of seeing this event," he observes. "Does
what you've seen so far make you a little more optimistic about what the
unwashed masses, or the 'semi-washed' masses, might see?"
Dr. Melissa McGrath takes the question. "The most
dramatic results we've seen so far, brightness-wise, have actually been in the
infrared," she states. In visible light, she believes, "it's unlikely
that this would have been seen." Her thinking is that the plume was very
small and close to the bright planet, which would require the high resolution
of the Hubble Space Telescope in order to see it.
But she would love to be proven wrong. She steals a quick
glance at her watch. "We know that the B impact is at 10:30," she states,
casting a meaningful glance at her colleagues, "and some of us
would actually like to go outside with our binoculars at 10:30 and look!" Laughter
erupts. "Because B's a lot bigger than A!" With 10:30 less than ten
minutes away, it's no wonder Melissa is on edge. Noting that Fragment A wasn't
as bright as B in visible light, she reiterates, "I think we should all go
look!"
It is more of a plea than a proposition. As heartbreaking as
it must be for her to miss this opportunity, she is too much the professional
to just march off the set and go outside. Alas, everyone else on the panel
seems to be determined -- or resigned -- to stick it out for the remainder of
the press conference. How can these astronomer-scientists be so composed, I
wonder, when they're on the verge of missing their one opportunity in a lifetime
to watch a comet hit a planet?
.jpg "Image of CometP/Shoemaker-Levy9 (1993e) Fragments Labeled with Letter Names")
passed a little too close and was ripped apart by Jupiter's gravity. The
resulting much smaller pieces will not have enough energy to sail past Jupiter when
they return this week. In May of last year, Brian G. Marsden of the Smithsonian
Astrophysical Observatory predicted that the entire chain of comet fragments
would collide with Jupiter this month.