Posted on 06/10/2005 10:05:27 AM PDT by Redcitizen
NASA space probe to slam into comet July 4 By Deborah Zabarenko Thu Jun 9, 5:00 PM ET
WASHINGTON (Reuters) - NASA's Deep Impact probe is scheduled to lob a big copper "bullet" into a comet on July 4 to look into the heart of this remnant from the formation of our solar system, scientists said on Thursday.
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Impact is expected at 1:52 a.m. EDT (0552 GMT) on U.S. Independence Day.
About a day before the collision, the Deep Impact craft will send a 317-pound (144 kg) copper-fortified impactor toward comet Tempel 1, which will be about 83 million miles from Earth.
The impactor will steer itself toward the comet and the Deep Impact craft will pass about 310 miles away from it and watch the smash-up, the scientists said at a briefing.
Rick Grammier, the project manager for the mission, called this maneuver "extremely challenging."
"It's a bullet trying to hit a second bullet with a third bullet, in the right place at the right time, watching the first two bullets and gathering the scientific data from that impact," Grammier said.
The Deep Impact mission is designed to offer a look under the surface of a comet, where material from the solar system's formation remains relatively unchanged.
Astronomers do not know what kind of impact they will see when the impactor hits: the crater produced on the comet could range in size from a large house to the size of a football stadium. Either way, it will not appreciably change the comet's path.
The crash is expected to eject a spray of ice and dust from the comet's surface and reveal the material beneath it on this Manhattan-sized space rock. At that point, the Deep Impact craft will have about 13 minutes to capture images and data before it weathers what astronomers expect will be a blizzard of particles thrown out of the nucleus of the comet.
There are cameras aboard the impactor and the main craft, and the crash will also be observed by the Hubble, Spitzer and Chandra space telescopes in addition to telescopes on Earth.
Because scientists do not know how bright the impact will be, they can't say whether backyard astronomers will be able to see it. But those with the best chance are those in the western United States and possibly New Zealand.
More information and images are available online at http:/www.nasa.gov/deepimpact.
bump
Observers in the far west of North America get lucky. Tempel 1 (just 3.5° northeast of Spica) will be in the southwestern sky, though getting rather low. The farther southwest you are the better. The comet will be in a fully dark sky 25° above the horizon for Los Angeles and San Francisco, and 22° up for Tucson. There will be no Moon. Seattle and Hawaii will be in evening twilight; the comet may be invisible from there during impact, depending on the exact timing.
The flash may be visible from earth.
You got that right "we hope it won't appreciably change the comet's path."
I would hate to see some Galactic Vonage commercial where we hit the thing and it veers off straight for us (reference the current Vonage commercial with the guy cutting down the tree and it hits his car).
ping
Bah! I'm in Virginia so I'm out of luck!
Hmmm, a tangible object "watching". Could there possibly be a tree, right now, watching me? So sinister. Instead of Big Brother watching it could be Big Object watching.
ya know, stooopid posts like yours are usually closely followed by Kitties and Lightning...
Uh...did you google this thread? Last paragraph.
After a voyage of 173 days and 431 million kilometers (268 million miles), NASA's Deep Impact spacecraft will get up-close and personal with comet Tempel 1 on July 4 (EDT).
The first of its kind, hyper-speed impact between space-borne iceberg and copper-fortified probe is scheduled for approximately 1:52 a.m. EDT on Independence Day (10:52 p.m. PDT on July 3). The potentially spectacular collision will be observed by the Deep Impact spacecraft, and ground and space-based observatories.
July
July 1, Friday
1 p.m. – 1:45 p.m. – Deep Impact Pre-Impact Mission Engineering Briefing - JPL (Interactive Media Briefing)
2 p.m. – 2:45 p.m. - Deep Impact Pre-Impact Mission Science Briefing - JPL (Interactive Media Briefing)
4 p.m. - 7 p.m. - Deep Impact Pre-Impact Live Interviews - JPL (One-Way Media Interviews)
July 3, Sunday
1 p.m. – 2 p.m. – Deep Impact Pre-Impact Update - JPL(Update on separation, navigation)
11:30 p.m. – 3:30 a.m. (July 4) – Deep Impact Commentary
DETAILS (times approximate):
11:30 p.m. to 12 a.m. - Beginning of Auto Nav. Interview w/ mission engineer
1 a.m. – 1:30 a.m. - Interviews, play animation, images from Impactor camera
1:30 a.m. – 1:50 a.m. - Listen to mission control
1:52 a.m. - Expected time of impact
2 a.m. - Possible start of images from flyby craft, images from Hawaii
3 a.m. - Commentary ends when telemetry resumes after shield-mode phase
(in both nominal and contingency scenarios)
July 4, Monday
4 a.m. – 5 a.m. – Deep Impact Post-Impact Press Conference - JPL (Interactive Media Briefing)
7 a.m. – 10 a.m. – Deep Impact Live Interviews - JPL (One-Way Media Interviews)
1 p.m. - 2 p.m. – Deep Impact Post-Impact Press Conference - JPL (Interactive Media Briefing)
All times Eastern. Programs may be pre-empted without advance notice.
Thanks for the tip OXEN. I printed it and will be watching. I am going to check with the local astronomy club to see where they are setting up here in Orange County, CA. I think we'll be able to see it.
I missed that. thanks.
Actually, despite the impression given by a couple of movies from years past, neither a tactical nuke, nor even a strategic H-bomb, would be able to "vaporize" a comet of this size, nor even put a serious dent in it.
Our nuclear weapons are powerful enough to do enormous damage to things on the human-sized scale, but we tend to forget how small that can be compared to many of the objects found in nature.
The largest thermonuclear weapon in our arsenal has a yield of about 50 megatons. That's 2.1 x 1017 Joules of energy. Using the best-case scenario (the comet is composed of nothing but ice -- no rock or metal -- and is no colder than the freezing point of water, and the nuke imparts all of its energy into the comet instead of radiating much of it into the surrounding space), and using the fact that it takes about 3014 Joules of energy to vaporize one gram of 32-degree(F) ice, we find that a 50-megaton nuclear weapon can vaporize no more than 2.1 x 1017 / 3014 = 7.0 x 1013 grams of the comet, which would make for a hemi-spherical crater of (2 x 7.0 x 1013)(1/3)/(4/3) * 2 = 77,887 cm in diameter, or 77887 / 2.54 / 12 = 2,555 feet across. Call it half a mile. And if there's any rock or metal material in the asteroid instead of just pure ice, the volume of the crater vaporized will be considerably smaller than that.
Compare that to the description of the size of the comet in the article: "Manhattan-sized space rock". This is rather imprecise, especially since Manhattan is extremely oblong (13 miles long by 2 miles wide), and comets tend to be pretty spherical, but let's conservatively say that this means the comet is a sphere five miles in diameter. A half-mile crater would be a minor blemish on its surface, and would come nowhere near vaporizing the whole comet -- the amount of (ice) material vaporized would only be 0.08% of the comet's total mass, or 1/1240th of it. You'd need more than another *thousand* 50-megaton strategic nukes to actually vaporize the comet -- again, if it's made of pure ice. Any rocky material would vastly increase the number of nukes required -- rock is a hell of a lot harder to vaporize than ice. And it would just laugh off a *tactical* nuke.
Remember the movie "Armageddon", where they split an asteroid "the size of Texas" in half with one nuke? Ain't gonna happen... That amount of energy, even if it *could* actually split the thing, wouldn't even be enough push the two halves apart against their own mutual gravitational attraction.
Similar calculations reveal just how freaking hard it would be to even deflect something of this size, unless you started *years* in advance of the expected impact.
Many people underestimate kinetic energy as an effective tool. If this comet were slammed with another comet of equal size going the opposite way at, say, 130,000 mph, there wouldn't be much left of either. Mostly just an ionized patch of gas, glowing at first and gradually fading out. It would probably create other problems in the solar system, especially with scientifc satellites and maybe Loral and other commsats.
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