Deep Impact Comet Bash, part 4

[coverage of Planetary Society’s Deep Impact Comet Bash: Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 ]

Break time is over. T-minus about 30 minutes to impact. We’re being shown computer animations of ejecta cones.. what might be comings up.. This is Bruce Betts presenting “Preview to an Impact” (by Peter Schultz at Brown University)

Next up: Bill Smythe, the payload manager for the Deep Impact mission…

People are monitoring NASA-TV if there’s new news. will go to NASA TV at about 7 minutes to impact.

To Bill Smythe… going to do the standard slide show on the mission.

I started building this thing about 5 years ago, and before that, the people that proposed the mission (it was first turned down, then took a a coupla years to alter and re-propose, after which it was approved. All of which took about 4 years.) Frankly I’m pretty nervous about what’s going to happen.

We know how to build spacecraft, but we don’t know what’s going to happen. Jets coming out of comet, They travel. 180 meters/second. We don’t know how strong the comet is, so we don’t know how big a hole it’s going to make. We don’t know how dense it is, how strong it is. We have a lot of clues. We spent about a year (early in mission) debating what comet looks like. Bumpy? Dish space? Cigar-spaced? yes, like cigar, .. once you’re launched from earth, you’re stuck with the orientation of the comet.

He’s showing an image, diagram of spacecraft: that gold platform pointy thing is the camera, that’s what I’m responsible for. 2 micro-radians… It’s the highest resolution camera ever launched into deep space. Why do you fly two cameras? one might break, and to give different perspectives. close up- and wider view.

Why go to the comet? We want to know what they’re like. How strong. In case one comes for us. We don’t know how they work at all. We don’t know what the shape of the nucleus is.. potato, craggy things. How do we get enough energy in there to have stuff keep coming off. Model: Hard rind outside, and inside, fluffy piece of snow stuck together. That’s the model we’re working with so far. Jets… melting temp lower than water, we think it’s carbon dioxide. Comets have hydrogen cyanide, formaldehyde, [and another one]. comets made of nasty stuff.

Comets and their secrets. Comets are composed of ice, dust and gas. (image of comet NEAT). Comets formed about 4.5 billion years. they tell how the solar system formed. Dust and gas spread around the sun in a big ball…

Program is interruped; we’re going to NASA TV
. The comet image.
We should be getting high rez images of the comet. up to 30 seconds before impact.

Back to the regular spiel. Messengers that come in from outside solar system where lots of comets were/are. These will give clues to what solar system composed of. At some stage in earth’s formation, hot hot with water all blown away. Something in the solar system brought the water back. We think it was the comets that did that. [whoa!! So that’s why Bill Nye began his presentation by guzzling a bottle of water… because the hypothesis is that comets populated this planet’s oceans with water.]

Elements of comet: ion tail, dust tail, coma (leading part), nucleus. We don’t know where the nucleus is. Hard to see a comet with all these things. The tail curves (sometimes) because the solar wind sweeps the comet out but the comet is moving, hence curve. Tails don’t always look like straight tails, have curliques and other shapes (look in comet book). Comets spin, but we don’t know how fast they spin.

Clue for how strong comets are: small… rotation rate of 10s of hours. Not very strong.

Comets might’ve brought water to earth, might’ve brought pre-biotic molecules to earth (stuff to make amino acids, basic stuff of life). Now he shows different earth-images of comet impacts: Meteor crater in Arizona. Picture of lake in Canada from an impact crater. The crater ring on Yucatan peninsula of Mexico [Doc M: That’s an SRTM image—Doc M. worked on SRTM]. Image of Mercury with impact patterns. Venus image of crater, Mars, far side of the moon.

See how strong comets are by seeing how they break up. Shoemaker Levy 9 and Jupiter. Broke up into 20-odd fragments. Saw some of it on Galileo mission. Impact of this little ball of copper, temperatures hotter than surface of the sun.

The point of impact… will happen very fast, cameras onboard take images every two seconds (i.e., they’re not capable of taking fully continuous images, so there are some unknowns about getting the actual impact).

What We Don’t Know…

We’re about 7 minutes from impact…. so we’re going to go to NASA TV
and come back to Smythe’s About Comets and About The Mission presentation later.

2 responses to “Deep Impact Comet Bash, part 4”

  1. Dori

    I’m watching NASA-TV while reloading your blog looking for new postings. So far, you’re much more interesting than they are.

  2. David Singer

    Thanks for the coverage, Susan — you’re telling me a lot more than NASA-TV (but they’re great for pictures).