Slashdot Mirror
First Results From Deep Impact Mission
jdoire wrote to mention a Physicsweb piece revealing some of the first bits of data from the Deep Impact mission. From the article: "Based on data from the flyby spacecraft and the impactor, Michael O'Hearn of the University of Maryland and colleagues say that Tempel 1 belongs to the Jupiter family of comets, although its overall shape and surface features are quite different from the nuclei of the two other comets that have been studied in detail -- Wild 2 and Borelly. They also report that Tempel 1 consists largely of extremely fine particles that seem to be very loosely bound together: in other words, the comet is more like a pile of powder than a solid rock." Looks like the Electric Universe folks were a bit off.
and their advertising application masquerading as a "website"
http://www.nasa.gov/mission_pages/deepimpact/medi
The same way the Shuttle on reentry 'impacts' the atmosphere, or the way a suicie from the Golden gate Bridge 'impacts' the water.
If you're moving fast enough, it's sure gonna feel like an impact.
____
~ |rip/\/\aster /\/\onkey
"Loosely bound" relative to solid rock. Also, from the article, although the outer layers of the comet were composed of tiny particles (~1 micron - 100 micron in size), the density of the comet's nucleus was about 600 kg per cubic metre, so the probe was never going to sink too far...
The comet seems to have survived:i media/addscolor90605.htmli media/1118923Fig7-90605.html
http://www.nasa.gov/mission_pages/deepimpact/mult
http://www.nasa.gov/mission_pages/deepimpact/mult
Procrastination -- because good things come to those who wait.
From the article:
So, if such comets are life seeders, maybe we just increased the likelihood of life evolving elsewhere in our solar system in a few billion years :-) How does it feel to be potential parents to an alien species?
Those who can make you believe absurdities can make you commit atrocities. - Voltaire
As I understand it a spongy asteroid will absorb much more force than a harder one of similar mass. Trying to break a sponge for example is far less fun than trying to break some silly figurine. I'm also guessing that the powder itself wouldn't be able to explode like (or at least to the same extent as) it would in an oxygen rich environment.
The lower layers of an object will not compact in a zero-gravity environment.
My Karma: ran over your Dogma
StrawberryFrog
The gravity and velocity of the comet i'm sure held it together. Your used to being on Earth, rules are a bit different when you leave the atmosphere. Matter tends to clump together, when that matter is in an orbit and moving at high velocities all together, it acts nearly as a solid. Despite that its a bunch of powder, you still calculate its center of gravity as though its solid. You are a bunch of cells but if I hit you, you don't fall apart. A bunch of powder moving in a direction will continue to move in that direction until acted upon by an outside force. The comet was big, the probe was small, the force not nearly large enough to knock it off oribt or to make the thing explode.
Regards,
Steve
...how is that there were an impact at all? Wouldn't the probe just sunk into the comet?
I'm guessing that what you're really asking is why any debris was thrown from the surface of the comet instead of the impactor just uneventfully sinking into the surface. Think of it like this: If you take a bowl and fill it with talc powder or flour (a very loosely bound together substance) and shoot a projectile into it with a slingshot, would it just sink in without producing any debris (a small puff of powder or flour)? Add to this the fact that there's far less gravity holding the comet together than there is holding the powder down/together (in the bowl). Does that visualization help?
It's an easy experiment. Try it. I might suggest a coffe can instead of a bowl though so that 1. you don't break the bowl and 2. you minimize the risk of the projectile flying back up and hitting you or someone/something else. Also use plenty of powder or flour as to slow the projectile enough that it can't hit the bottom and bounce back up and of course you want to wear safety glasses. Alternatively you could just view the images sent back from the mission (included in TFA) and trust that it's not all just a hoax.
If you can't just be yourself, then be more like me, ok?
Correct, but the point remains: the comet was described as having the consitency of a snowdift.
On the surface of earth, the bottom of a snowdrift compacts under the weight of snow on top of it. On a comet (i.e. a small body in a large orbital path around the sun) the same effect does not apply, and the snowdrift could be as loose as the top inch all the way through.
My Karma: ran over your Dogma
StrawberryFrog
http://en.wikipedia.org/wiki/Tunguska_event
e nt_040812.html
There have been a wide range of theories about this, but a puffball comet explains a lot about what happened there. From Aliens;
http://www.space.com/scienceastronomy/tunguska_ev
to Victorian Era Superweapons testing ala League of Extraordinary Gentlemen (the Comic book, not the movie). I have tried to find the site on Google Earth but have not been lucky.
Sorry about the writing. Robot fingers, you know? Cliff Steele in DOOM PATROL #23
Water's density is 1000 kg/m^3, so 600 kg/m^3 is pretty dense.
617B3B7F7E7C7D7F00EOF
The military is currently researching railgun technology. The shells said railgun will fire are inert and will not explode in the same manner as conventional shells. They'll simply strike the unfortunate target with such force that it'll basically explode. Nasa did the same thing, just with more mass and more velocity, no chemical reaction could explode with the same force obtained by striking a target in this manner.
You've got many many metric tons of snowdrift, floating through space.
You ram a refridgerator size probe REAL fast into one side of it.
The 'snow' right where the fridge hits is going to move inward, but the many many metric tons of snow on the other side of it is going to want to stay right where they are (a body at rest tends to stay at rest). The movement inward of the snow under the probe's impact against all that 'resting mass' will cause the compression of the 'snow' in that area.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
I can't think up a good answer beyond the usual origins of life or origins of the solar system stuff. It's not really practical for the layman, but it's interesting to scientists. I hold to the idea that the pursuit of knowledge in and of itself is a noble pursuit.
On the other hand, I do hear quite often "why should I care?" from laymen. Well, turn back 100 years to the beginnings of quantum theory. "Why should I care how electrons behave around protons" or "Why should I care that uranium undergoes fission when bombarded by neutrons?" The first led to the development of the transistor and electronics and computers and just about everything technological in the past 50 years. The second led to the development of nuclear power (and weapons) and has also had a tremendous impact. By the same token "Why should I care what comets are made of?" may not have an answer now, but it might in the future. To withold funding from one scientific project may prevent some new discovery or technological advance. If all scientific endeavours were left to private industry, sure we'd make advances, but most private research is focused on the near term whereas public research is knowledge for knowledge's sake, and often produces advances and breakthroughs not seen in private research. In NASA's case, their investment in the 50's and 60's led to quite a few developments such as communication satellites and paved the way for businesses like Scaled Composites. That's at least worth something. I know I'm proselytizing a bit, but I think I have at least some of a point.