[FPSPACE] Looking for a vision

[E.P. Grondine]

> When I started reporting on the NEO hazard, both
> George Brown Jr. and Eugene Shoemaker were still
> alive. I never thought that some 12 years later
> senior NASA management would still be doing its
> best to avoid dealing with this hazard.

That's because NASA should only be concerned with 
detecting NEOs and not at this stage be directed
to consider deflecting anything. When given such
a dual direction, critics of NASA are in effect
given carte blanche to argue that not enough funds
go to deflection preparedness.

>>No it isn't a lack of clear instructions 
>>concerning detection/deflection. 
>>There are several reasons for NASA's lack of
>>action. 
>>First, it's because Morrison refuses to admit 
>>to comet fragment impacts. With Shoemaker dead
>>there's no one to stop him.
>> Second, because many within NASA are 
>>concerned with the nuclear devices which will 
>>have to be used for deflection, there tends to 
>>be an understatement of the hazard. 
>>Third, the detection contract was awarded to 
>>JPL instead of Morrison at Ames and Arizona.
>>Four, NASA management was controlled by "manned
>>Mars enthusiasts" who didn't want to see any 
>>resources diverted from their obsession.
>> No one said deflection itself should be NASA's 
>>responsibility, other than making theoretical 
>>studies, because the tools required for 
>>deflection, which are dual use, have military 
>>use as well.
>>But NASA was instructed to find everything down
>>to 140 meters, which instructions they promptly 
>>ignored.
>> With George Brown Jr. dead, there's no one to
>> call them on it.

Once NASA enters the detection business in earnest,
some asteroid or comet fragment will soon be
identified to be on a collision course with Earth.
Most likely a Tunguska-sized asteroid, and several
centuries hence. 

>>Actually, Jens, we will be in the midst of 
>>Comet Schwassmann Wachmann 3's debris stream in 
>>2022, if we don't get blind-sided by anything 
>>before then. Based on Rio Curara (1930) and 
>>Rupunini (1935) we will have problems

It's unlikely that any action needs to be taken though, since over time it will
become apparent approximately where the impact is
due to take place. 

>>It is highly unlikely that any impact point will be
>>predictable well in advance, given what is now know about 
>>the behavior of comet fragments. The can outgas
>>and/or fragment.

In the improbable case that a behemoth object is
found heading our way - maybe a comet fragment -

>>It doesn't take a behemoth fragment. And impact 
>>isnot improbable, but certain, for all types and 
>>classes of impactor.

then the matter should move from NASA up to the
White House. It's not to be expected of NASA that
they roll a ready-made deflection plan out their
corporate sleeve.
>>I don't expect NASA to implement deflection.

And yes, other national or supranational agencies
should work along the same lines.

>>Yes. 
>>Other nations will also be working on anything
>>inbound then.

> As you are undoubtedly aware, for its own internal
> reasons NASA has been relying on Morrison's estimate
> that asteroids are 95% of the threat, while comets
> are only 5%. I believe you and I both are fairly
> certain that these numbers are wrong, and that the
> ELEs are due to cometary impact, and have been
> occurring at a roughly regular rate of 1 per
> 26 million years. In other words, Clube and Napier
> were right on the injection mechanism and Morrison
> and Muller wrong. 
>
> What that works out to hourly I don't know.

It's a three-dimensional problem, isn't it? You
focus on the comet versus asteroid ( ie. orbit
type ) dimension, which is indeed important.

>> It has many more dimensions than three, and a lot 
>> of them are human dimensions.

>>I focus on reflectivity. Dead comet fragments are 
>>as reflective as charcoal. I also focus on the
>>velocity, and warning times, and detectors, 
>>and sizes.

>>For ELEs, based on Comet Shoemaker Levy 9, with 
>>current detectors we will have well less than 2 years
>>to react.

But it's equally important where on the scale from
50m to 20km the object belongs. And whether the
impact is due this decade, century, millennium,
or later, ie. the time dimension.

>>Yes it is important to form a reliable estimate
>>of the hazard, and the types of impactors.

I agree with you that comets are unlikely to make
up only 5% of the ELE threat. Do you suggest 50%
or more?

>>Yes. Probably nearly 100% of ELE. 

On the other hand I find it hard to disagree with
an estimate of 95% of Tunguska-sized impacts to
stem from asteroids.

>>You need to read my book. 

As for the validity of my rule of thumb, it
obviously depends

>>on something other than the data.

>>E.P. Grondine
>>Man and Impact in the Americas

--
Jens Kieffer-Olsen
Slagelse, Denmark

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