February 20, 1958

Prof. H. Petterson
Geophysical Departasnat
University of Hawaii
T. Ae

Desy Prof. Petterson:

T have just noted your erticle on the acoretion of cosmic dust
in the February 1 Nature. You may think it strange to have 4 ccimmui-

cation from a geneticist, but I beldeve the enclosed memorandua will
exniain the basis of it.

May I enquire just how much air you did conveniently sample on
filter? I am interestsd in the possibility of some studies on such
samples ag a prelininary to more presumptuous investigations. Would

you care to discuss the exchange of samples for microbiological analysis?
Of course, any positive results in this Pasteurian type of experiment
would be highly questionable but they might help to ussess the diffi-
entties in planning mere ambitious (extra-terrestriel) oxperiments.

I would asanwhile appreciate the favor cf a reprint of your article,
sm! references to your other publications that might be helpful.

Yours sinceraly,

Joshua Lederberg
Professor of Medical Genetica

JL/ on
encl,

PS. fT uplers tani your figures correctly, the flux is about
50 mg M2 yro}, Is that right?