NASA is hot to high-energy impact a comet. When I ran the numbers I got 4.2x10^10 joules or almost exactly 10 tonnes of TNT equivalent. (Assuming the English units are correct, do the metric conversions yourself. NASA creative bookkeeping strikes again.) NASA wants to spurt up a bunch of vaparized comet to do spectroscopy and see what is in there. However...

Comets, by whatever model you choose, are not well consolidated. An 820 pound impactor a yard across packing 10 tonnes of TNT equivalent of kinetic energy is the ever so sharp tip of an icepick screaming into a block of dirty ice at 6.6 miles/second. Upon impact it will transform into a directed dense hypersonic plasma jet as it passes through a few times its own mass of comet - still going forward. That is how a shaped explosive penetrates armor. The icepick tip is now a buried hollow point bullet. It will bloom and suddenly deposit energy deeply subsurface.

The Official Truth

The most likely scenario of a small dense body hypersonically (6.6 miles/second, Mach 33) impacting a low density loosely consolidated weakly gravitationally bound 3.7-mile diameter body is to burst it. Check out a high velocity small caliber hollow point bullet hitting a watermelon. SPLAT! One sees the same behavior in a hollow point bullet entering a transparent block of ballistic gelatin: a thin penetration line terminates in a huge internal cavity suddenly billowing. Comets are brittle not elastic.

NASA says they will dig a crater seven stories deep and 300 feet wide at the surface. (The resulting thrust changing the comet's orbit is, ah, ignored.) Uncle Al predicts NASA will shatter comet Tempel 1 and suddenly have all sorts of good reasons to begin frantic no-budget-is-too-large studies. The party is PERTed for birth on 04 July 2005. Knocking a big chip off the old block with a coincidentally lethal Earth-bound trajectory would do it.

Kool, Uncle Al!


"The most likely scenario of a small dense body hypersonically (6.6 miles/second, Mach 33)..."

What's a nice Mach number like 33 doing in interplanetary vacuum? What's the speed of sound along most of Tempel 1's orbit? :rolleyes:

I hope Uncle Al is correct. I'd like to be watching through my scope when it hits.

We need something to focus our species on something more important than the World Series or Survivor.

I hope they have ensured the angle is correct enough to not have any bits hit the earth.

I cant help but feel this is a rather stupid move of them :|

Perhaps there were some slow comets at the early time of earth accretion and a bit after. I mean, able to bring both water and organic molecules gently on the surface. I've read somewhere that artificial collision have been done with water+two amino-acids and spectro analyse af the impact residue contained a peptide mixture of the two amino-acids.