STANFORD UNIVERSITY MEDICAL CENTER

                         STANFORD, CALIFORNIA 94305 o (415) 321-1200

                       March 6, 1973

STANFORD UNWERSITY SCHOOL OF MEDICINE
Deportment of Genetics

Ref.:  825-CBF:mo

Dr. Croften Barney Farmer _
Jet Propulsion Laboratory
California Institute of Technology
4800 Oak Grove Drive
Pasadena, California 91103

Dear Barney,

Thank you for sending the figures.

  In the light of the equilibrium to which the cryobiological
discussion may be tending I think it would be most valuable if you
would use another object parameter in your calculations: namely the
occurrence of ice at a maximum temperature of 260K. If I read J>ur
figure 9 correc?y this would allow for a subl=on rate of 5p/min
at 1Omb atmospheric pressure which seem like plausible values to take.
On a full frosting model, say 30~ every morning, this could give our
bugs all of 6 minutes during the warming sycle during which they could
acquire their necessary moisture; then, of course, we have to postulate
that they are adapted to much lower water activities for their continued
internal metabolism at still higher temperatures. Mixing the frost in with
soil should allow still further improvements on these parameters whether
or not one succeeds in making a persuasive case for reaching the liquid
state for any period of time. We still end up with the idea that either
the Martian bugs have an extremely short period during which they can
actively grow during a diurnal cycle or else that they have an adaptation
to aridity that goes far beyond anything to which any earthly organism
has adapted. These are both discouraging prospects, and ones to which
the actual Viking biology experiments have not really addressed themselves;
nevertheless, they really do not foreclose the possibility of a vigorous
biosystem.

   On the other hand, if we can get sufficiently far north to reach the
southern-most extension of the annual cap there then should be a fairly
substantial winter deposit that persists for some time before it sublimes
away -- which is, of course, exactly what we observe every summer. The
question remains how much of this is under a regime that exceeds the 260
1imit;which is a point possibly only slightly more comfortable than the
previously asserted 273,but perhaps just enough that we might have a
reasonable persuasiveness in propounding it.

  On this model Martian life might be confined to a fairly narrow
subpolar zone which, of course, remains as the rationale for the proposed
B mission. These organisms will, of course, have internal "liquid water"
kept from freezing by solutes and perhaps even by the evolved reliance
upon solutes which are particularly efficient in injuring crystallization.
When water is maintained in compartments individually as small as lp dimension

over

LT. J. P. KENNEDY, JR. LABORATORIES FOR MOLECULAR MFlDlCINE, DEDICATRD TO RESMRCH IN MENTAL RETARDAT:ON

MOLECULAR BIOLOGY               HEREDITY              NEUROBIOLOGY            DEVELOPMENTAL MEDICINE


Dr. Croften Barney Farmer            -2-

3/6/73

it can, as you know, be supercooled quite extensively without running
much risk of crystallization. But for this discussion I do rely mainly '
on the reported observation of microbial growth down very close to 260
as remarked in Wolf's letter.

  If there are organisms at the top of the water chain that can
extract moisture at 260 there will surely be pred4tors which will use
these as the primary source of their own moisture and can function
presumably at much higher temperatures. This phenomenon would be more
characteristic of the intermittent distribution of ice as might be
expected in the tropical zone with shaded areas. So, there is obviously
every reason to try to validate this model which could be done by the
mere observation of frost reaching the ground even in terrain of low relief,
such as we presumably seek for the landing of the A mission.

  It is still extremely important to look for the possible variances
around the "average extreme temperatures" calculated by Kieffer.

  My summary recommendation would be to target mission B just as far
north as we can credibly predict the occasional occurrence of reaching
the 260 threshhold for at least a few days a year. It would be better if
our landing time coincided with this but not absolutely crucial as we
should still be able to find the hybernating forms and the fall traces of
the summer's growth.

Sincerely yours,

Joshua Lederberg
Professor of Genetics

JL/rr