Subject: Sound bites on asteroid searches

From: David Morrison

Submitted: Wed, 26 Feb 2003 09:33:55 -0800

Message number: 80 (previous: 79, next: 81 up: Index)

Colleagues:

This is a follow-up to my note yesterday about the non-statistical 
nature of an asteroid search carried out for the purposes of 
planetary defense. You may be interested in the following "sound 
bite" statements that I have found can help to make these and related 
points. (Reactions are welcome, especially if you don't agree with 
any of these statements.)

David Morrison

==================================

In the real world, impacts are deterministic: There either is or is 
not an asteroid that will collide with Earth during this century.

Asteroids do not change orbits capriciously except in Hollywood.

We already know the statistics and the risks -- what we need now is 
to search for individual objects, one at a time. The public 
requirement is to find the next impactor before the Earth collides 
with it.

Many science objectives can be met with statistical samples, but 
planetary defense requires a complete survey.

The public does not care if the annual risk of dying from an impact 
is one in a million or one in two million -- they want to know if it 
will happen to them.

When you cross a busy intersection, you don't ask what the statistics 
are on pedestrian accidents -- you look to see if a car or truck is 
headed toward you.

There is no last-minute warning system: Either we discover an 
asteroid and predict its impact decades or centuries in advance, or 
else it strikes without warning -- the first you will know is when 
the sky lights up and the ground starts to shake.

The individual risk is dominated by objects large enough to produce a 
global environmental disaster -- one that places you at risk anywhere 
on the planet.

The most likely impact is a small one, but the most likely impact to 
endanger you (or any individual) is a big one.

A large country (like Russia, China, USA) is more likely to be hit, 
but its citizens are no more at risk than those of a small country.

We have a choice: Deal with the small impacts that hit more 
frequently but pose very low risk, or deal with the large ones that 
are infrequent but are more likely to kill you. (The current 
Spaceguard Survey deals with the large ones that pose the greatest 
risk)

You have more to fear from the residual 10% of big ones that 
Spaceguard will not have found by 2008 than from the sum of all the 
smaller asteroids.

Small cometary impacts (<1 km) are a negligible hazard for the simple 
reason that there are few if any such small comets.

The probability of being killed by an asteroid is very low, but it is 
larger than the chances of being killed by many other things (e.g., 
defective food or drugs, or leakage from nuclear power plants) that 
governments take very seriously.

Impacts are the extreme example of a hazard of very low probability 
but very great consequences.

Impacts are the only known natural hazard that could destroy civilization.

Asteroid impacts are the only known natural hazard that can be 
eliminated entirely by appropriate application of technology.


-- 
+++++++++++++++++++++++++++++++++++++++++++

David Morrison, NASA Ames Research Center 240-1
Tel 650 604 5094; Fax 650 604 4251
david.morrison@arc.nasa.gov or dmorrison@arc.nasa.gov
website: http://astrobiology.arc.nasa.gov
website: http://nai.arc.nasa.gov
website: http://impact.arc.nasa.gov

LSST LSST LSST LSST LSST    Mailing List Server   LSST LSST LSST LSST LSST LSST
LSST
LSST  This is message 80 in the lsst-general archive, URL
LSST         http://www.astro.princeton.edu/~dss/LSST/lsst-general/msg.80.html
LSST         http://www.astro.princeton.edu/cgi-bin/LSSTmailinglists.pl/show_subscription?list=lsst-general
LSST  The index is at http://www.astro.princeton.edu/~dss/LSST/lsst-general/INDEX.html
LSST  To join/leave the list, send mail to lsst-request@astro.princeton.edu
LSST  To post a message, mail it to lsst-general@astro.princeton.edu
LSST
LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST LSST