March 29, 1960

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Dr. JohnlA. O'Keefe
Theoret | on

Goddard Spece Filght Center
8719 Colesville Road
Silver Spring, Maryland

Dear Or. O'Keefe:

Thank you for your letter of March lith. J would certainly be
very enthusiastic about following up the approaches suggested in your
letter. We have already discussed some simller projects bus 1 do
not belleve any of them is being actively studied. The survivorship
of bacterla In chemical explosions has been studied by the Biological
Warfare Laboratories at Fort Detrick and it might be worthwhile to
consult Or. Charles Phillips there for currant Information that might
relate to your suggestion. There is another possible hazard to smal!
particles of certain sizes that Jikewlse deserves further Investigation.
This would be the Tabor Effect which would apply to particles of
approximately micron size. Werner Suom!l belfeves that such particles
would have great difficulty in resirradiating at Infrared weve lengths
larger than thelr own dimensions. However, they could sttll efficiently
absorb at lower wave lenghts. Consequently, their equilibrium temperatures
might be very high indeed. Smaller particles would be exposed to the
shorter ultraviolet and the corpuscular radiation without shielding
and be destroyed by these. {f these arguments’ are true the smallest
effective vehicle for surviving organisms would have to be et least
several microns in diameter. Is the Tabor Effect well enough understood
that its application to the present case would be entirely straight-
forward?

Your suggestion, the frequency of microorganisms at high altitudes,
Is an extremely important one‘cn many counts. Belleve it or not, we
have no really useful data or the frequency at altitudes above about
30,000 feet? There ere many rasons why the detalled profile of
bacterlaebearing dust should te Intensively studied. At one time
there were strong arguments tio doubt that such particles could be
carried above the tropopause ‘but now that turbulence, even in the
lonosphere, Is a more respedtable concept the whole question should
perhaps be reinvestigated. © Certainly bacteria should be among the most
reliable indices of terrestrial origin. At very high altitudes efforts
should be made to collect ‘micrometeorites on sterile filters end on
non-carbonaceous fliters In order to establish the incidence of
1) microorganisms, and 2) perticles comprised of carbor, nitroyen etc.
which should be abundent among meteoroids of cometary origin.
-2-

These experiments would quite appropriately relate to probes on
balloons, rockets and recoverable satellites In order to sample
various altitudes. Once again the Biological Warfare Laboratories
should have both the interest and experience to tie Into such a
program. { will be very happy to lend any possible assistance to
this.

In principle your third suggestion Is equally promising.
However, the difficulty with studying any object that has reached
the earth's surface Is the uncertainty whether it may be contaminated
by terrestrial materials. A level of contamination that would be
chemically insignificant could make the investigation worthless from
a blological point of view. However, | certainly agree that all
such objects should be carefully analysed not only for their mineral
constituents but also for the carbonaceous compounds which have been
all but ignored in past studies. Calvin's recent findings on
carbonaceous chondrites are most exciting.

We have learned absolutely nothing about the Russian program
In exoblology except the bare statements, of which you must already
be aware, that they are taking due precautions. | do not think that
decontamination presents any serious fundamental problems; of course
a successful program does require a sincere concern for the problem
and a consequent willingness to take some pains In the treatment and
handling of the payloads. While a formidable effort may therefore
be necessary, It should still be relatively insignificant compared to
the goals at stake and to the other effort that goes into the development
of the vehicles and the payloads.

Mr. Derbyshire at the Space Science Board Secretariat, has a number
of reports from the exobiology subcommittee of the Space Science Board.
These are, of course, transmitted to NASA In a formal way but | am
sure that he would be happy to furnish additional coples and to be of
any additional assistance possible.

t'm also sending a copy of this reply to Clark Randt In the new
office of Life Sciences; we have, of course, been discussing some of
these projects and that office should be instrumental in helping to
get them underway.

Yours sincerely,

Joshua Lederberg
Professor of Genetics

cC: Or. Clark Randt
Dr. Robert Jast row