CALIFORNIA INSTITUTE OF TECHNOLOGY
PASADENA, CALIFORNIA

DIVISION OF BIOLOGY

Jamary 30, 1960

Dr. J. Lederberg

Department of Genetics

Stanford University School of Medicine
Palo Alto, Calif.

Dear Josh,

Thanks for your memo (Westex 5=1) and draft copy of "Exobiologye"
I could, if necessary, attend the meeting at Stanford on Feb. 29, but
it would entail some difficulties, and I would therefore prefer not to
come unless, as you say, some urgent exobiological business is to be
considered.

I have read "Exobiology" and think it is a very good summary of
the position and program. I am still unconvinced of the danger of back~
contamination. Three improbable assumptions are involved here: (a)
that microorganisms will be found on the planets, (b) that they will be
dangerous to man, and (c) that we would be unable to cope with them if
they escaped. The product of these 3 terms is so much smaller than any-
thing else we have to consider--in particular, the danger of "forward"
contamination--that I think it detracts from the plausibility of the
program as a whole to give it much weight. Fersonally, I would be wil-
ling to run the risk involved in a premature return trip, if a less bold
schedule meant that a sample of Martian soil could not be brought back
to earth in my lifetime.

Looking forward to seeing you and Esther here in March.

Best regards,

7 Norm Horowitz

J FEB1 1960