IN REPLY REFER TO:

JAN 111965

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WasuinctTon, D.C. 20546

SB(FHQ: pak) 7 January 1965

AIR MATL

Dr. Joshua Lederberg
Department of Genetics
Stanford University
School of Medicine

300 Pasteur Drive
Palo Alto, California

Dear Josh:

Dr. Reynolds and I have recently completed a careful reading
of your stimulating paper on "Signs of Life: The Criterion -
System of Exobiology."

We have only a few comments to make at this time:

The excellent paragraphs on optical activity ended with the
statement that "Enantiomorphs can be assayed with optically
active reagents to give resolvable diastereo-isomers, and
exploit the most sensitive methods known to chemistry."
Several pages later under Instrumentation you speak of
"nolar rotations being small,” and suggest that some method
of excitins the signal would enormously enhance the power of
this technique. Did you separate this discussion for any
special reason?

Your paper emphasizes the chemical scan and the sensitivity

of chemical measurements. It seems to us that there may be a
hazard in establishing such a requirement for all life-related
substances. Cannot some methods be too sensitive, or unnecessarily
sensitive? All of us have seen the results of good organic
chemists, with blanks and other precautions -- who when reporting
a few parts per million, could not be sure that the material was
indigenous to the sample or already present as a contaminant in
the instrument hardware, in "the columns", or introduced during
one of the stages of preparation and assay. At any rate we

have some reservations that all crucialdata for exobiology
hinge on 10Y to 10° molecules in a 1 cm cell.
We wondered a bit why you developed 15 pages of criteria and only 2
pages on instrumentation for such criteria, particularly since you
had in an earlier report developed a good case for what you called
"A Crises in Instrumentation." We did note that you wrote favorably
concerning the gas chromatograph - mass spectrometer combination

and are happy about this, since we have recently undertaken to
develop such an instrument for flight.

The interplanetary barrier certainly requires repeated emphasis,
however, it is hoped that we can solve this problem without the

delay and expense of a lunar base. This is particularly true since

a quarter million miles may be merely a dog-leg route for contamination
in both directions. We prefer to avoid the hazards of back
contamination by one-way unmanned missions to Mars. As for the risk

of contaminating Mars by these missions, there is a growing confidence
now that such risk can be reduced to an acceptable level. This
confidence is based upon an ever increasing list of heat resistant
electronic components, materials, and instruments. Some of these

items are intrinsically heat sterilizable and many others are being

so designed. Also procedures and heat treatment cycles are progressing
well beyond what we had expected. Preliminary results on many aspects
of this overall problem look very encouraging.

It is our hope that an international sense of moral responsibility
on this matter will develop. This may indeed be the case if the
United States presents a valid argument for spacecraft sterilization
and a procedure which is within the technological capability of the
USSR. Thus far, we believe it only our good fortune that Russia's
deep probe guidance capability Leaves the question open for further
study and consideration. The solution may be to make not only an
initial but a somewhat complete exploration of Mars while it is yet
an “unvisited"” body in our solar system, and to do so as early as
reasonable decontamination precautions permit.

Please accept our sincere appreciation for another vigorous and
interesting treatment of exobiology subject matter.

Sincerely,

——T
e a VAL nia,

Freeman H. Quimby

Chief, Exobiology

Bioscience Programs

Office of Space Science
and Applications