Vince,

This mission is one of several NASA is mounting which will help us characterize the left over planetesimals in our system. All will help if we need to eventually divert a potential impactor. This mission is important in its ability to show how a heavy blow will affect a comet. There is much concern wheather a nuclear blast will have the diversionary effect we wish or simply break up a comet into a few pieces which migh have an even worse impact.

For more information please review the sources in rebuttal to the top 5 dumb impact comments I've heard recently.

Top 5 stupid Impact Comments

1) We need a man tended lunar telescope to detect small impactors.

We don't. While current detection scopes can detect the smallest possible impactors at near miss distances they can only routinely detect NEOs greater than about 340m (< magnitude 20.5) and PHAs greater than about 270m (< magnitude 21.0) . While we are detecting these well enough to survey most of them over decades to about a century we need large ground scopes or small orbiting facilities to detect them in the 10 year time frame targeted for the > 1 km objects. Such scopes would be able to detect 100 km objects over the time frame listed above for roughly 300 m objects. Large orbiting facilities could be used for detecting these smaller objects per David Morrison in a personal communication. See item 3 below for supporting data.

A man tended lunar scope would be useful for detecting smaller impactors. It simply isn't cost effective given the development costs required to re-establish manned lunar capability and the per mission cost of at least 500 million assuming shuttle type cost structure. It is simply another one of those justifications for returning to the Moon such as He3 which have far cheaper and more technologically feasible alternatives.

2) We have the technology to divert long period comets.

We don't. Long period comets typically range from a few kilometers to tens of kilometers in diameter. The chief limit is detection as Duncan Steel tried to explain to EP in "GRONDINE'S MISREPRESENTATIONS" at http://abob.libs.uga.edu/bobk/ccc/cc042401.html . The explanation obviously went over Grondine's head as he still makes this claim.

Secondary limitations include improving, demonstrating, and testing the technological options we think will be needed. You can find the opinions of experts on this issue at: http://www.llnl.gov/planetary/

In summary as Clark Chapman stated in his 1998 Congressional testimony at: http://impact.arc.nasa.gov/congress/1998_may/chapman.html "It takes a truly huge object like Eros, or like the comet in the movie “Deep Impact,” to threaten mass extinctions of species. Fortunately, Eros cannot strike Earth in the near future. And impacts of such magnitude occur extremely rarely, once in perhaps 100 million years. That’s only one chance in a million of happening during the 21st century: really unlikely! It is an appropriate topic for science fiction, but nothing to worry about. Such a body is so large, there’s little we could do about an Extinction Level Event, anyway (“Deep Impact” notwithstanding)."

3) Only 2 NEOs less than 1 km have been found.

This is even more preposterous than the lunar scope claim for shear lack of checking easily available data.

You can visit the minor planet centers NEO lists to find that it has been many years since this statement was true. http://cfa-www.harvard.edu/iau/lists/Amors.html
http://cfa-www.harvard.edu/iau/lists/Apollos.html
http://cfa-www.harvard.edu/iau/lists/Atens.html
You may also need http://cfa-www.harvard.edu/iau/lists/Sizes.html to convert magnitudes to diameters.

You can get a quick idea of the current distribution of detected NEOs and PHAs at

4) We don't need a heavy lift vehicle to return to the Moon.

This is of course why human missions to the Moon are so common today.

5) Our current emphasis on NEOs > 1km is dictated solely by limited funding.

The current choice to detect objects > 1km is based in part on limited funding, but this limitation is considered acceptable to many impact researchers because these objects account for most of the threat in terms of average fatality rates and the fact that there are many other sources of fatalities worldwide which have higher expected average death tolls which could be substantially reduced with additional funding. Disease control and better severe weather warning and evacuation capabilities are some examples.

The relative impact of various causes of death can be found at:
http://impact.arc.nasa.gov/congress/1998_may/chapman.html (hazard table)
http://impact.arc.nasa.gov/congress/1998_may/fig1.html (indicating impact of Tunguska style events is three orders of magnitude smaller than global scale impactor on an average annual basis and 5 orders smaller on an individual event basis)

Regards,
Mark