Impactor ejects mighty water mass (BBC)

[eppur_se_muova]

By Jonathan Amos
BBC News science reporter, in Leicester

The Nasa projectile that slammed into Comet Tempel 1 last year kicked out at least 250,000 tonnes of water.

Swift's X-ray data shows more water was released and over a longer time scale than had previously been thought.
***
But whilst the other observatories made relatively quick studies and then turned away, Swift continued to look at the impacted "ice mountain" on and off for more than 60 days. Its patience paid off.

Swift's X-ray Telescope (XRT) saw the comet continue to release water for some 13 days after the initial event, with a peak five days on from the collision.
***
more at: http://news.bbc.co.uk/2/hi/science/nature/4871934.stm

[patrice]

1. . . . . produces space fog?

[htuttle]

2. Something's been going through my mind since I read this

I'm wondering if this would have any impact on the comet's trajectory. A 'jet' for 13 days, I mean. I know the comet is very large compared to the impactor, but it hit it pretty fast, didn't it?

Did the heat from the impact vaporize some ice? Did the comet have a 'skin' that the impactor pierced? The article seems to indicate that more ejecta was produced than would be expected from the force that hit it -- though I don't see how they could know that, given that they didn't know the structural composition of comets. That was the point of this experiment, I believe.

Anyway, I hope they keep an eye on it...

[Dead_Parrot]

3. Probably not

The jet may have done some weird and wonderful things that weren't expected, but the total energy of the jet can only be equal to, or less than, the kinetic energy of the probe. Working out out the maximum orbital change is a pretty simple sum involving momentum and mass for the two bodies...

[htuttle]

4. That's what I would have thought

But the article says that there was an unexpectedly large emission of material -- as in more energy released than transmitted.

That made me think of a pierced balloon flying around the room for some reason...:o

[Canuckistanian]

5. That's what I think, too

It appears as if there's a thin layer of denser rocky material surrounding a mostly ice core.

And, since the comet is within the range of the sun's "melting energy", the hole punched by the projectile caused a local deep melted hole that poured out all this water.

By the sound of it, this has almost certainly changed the trajectory of the comet.

[Dead_Parrot]

8. lol...

I think it means they just got the composition wrong (which is why the experiement was done in the first place), but I prefer your version... :)

[OhioNerd]

9. One does not equal the other.

OK, that doesn't make sense, but the board makes me use those title things and they can't all be gems.

What I'm trying to say is, it's not that more energy was released than expected, it's that the result was unexpected.

[eppur_se_muova]

10. Even if they hit the aliens' fuel dump?

I keep thinking these guys are going to come kick our collective ass any day now...

[rayofreason]

15. not quite

"the total energy of the jet can only be equal to, or less than, the kinetic energy of the probe."

Not quite true. As sunlight is absorbed and the water sublimates out it carries mass and momentum.


"Working out out the maximum orbital change is a pretty simple sum involving momentum and mass for the two bodies..."

True, but you must include the momentum of the jet.

[sutz12]

6. I would hope that they were watching for this....

after all, one of our main concerns on a planetary scale are the big impacters. It would surprise me greatly if they didn't measure the amount of deflection the impact caused. From that standpoint, the extra loss of material and extended time of the 'jet' of watercould be goog news. It would indicate it might be easier to deflect a cometary impactor than first thought.

[Dead_Parrot]

7. They will be doing...

Pinning down a precise orbit takes many months, sometimes years: It will probably be a while before they have a definitive answer to the new trajectory.

[Ready4Change]

11. Does the comet have any rotation?

If it rotates very quikly at all, the jet would likely be squirting around in different directions. Much of the potential vector change might be canceled out?

[sutz12]

12. Good question...

Most bodies rotate some, the question is how much, I guess. Even so, if targeted properly vis-a-vis the axis of rotation, this could be accounted for.

Obviously, this wouldn't matter much for a rocky impactor, an asteroid.

But if this helps us figure out how to deflect a comet, that is part of the battle against potential planet killers.

[eppur_se_muova]

13. You're not the only one concerned ... (LINK)

Astrologer sues Nasa over probe (BBC)

A Russian astrologer is suing Nasa for crashing a probe into a comet, claiming it has distorted her horoscope.

Marina Bai is seeking $300m (£170m) in damages, saying the probe's impact on Comet Tempel 1 violated her "life and spiritual values".

http://news.bbc.co.uk/2/hi/europe/4649423.stm

[sutz12]

14. I guess it was only a matter of time....

:shrug: :rofl: