wie Of Lig Peat , woh be wa cw tea e

Life Presented at an Informal Meeting on Dec. nser hy 2 750

Among the participants were: Coryeli, Doty, C ld,
Kaplan, Kamen, Levinthal, Luria, Rossi, Sistrom, Strandberz, Wat: n and
Whipple.

A.__ PURPOSE

In the next very few years space on both :‘ srrestrial
satellites and martian (or venutian) probes will be available for biological
observation. The purpose of the meeting was to discuss whei Kinds of bio~
logical questions it would be most profitable to ask, The «eting concerned
itself with questions about the existence and neture of ex ra-terrestrial
living things, not with the behavior of terrestrial livinr things in space.

Bo THE PROBLEM

In considering extre-terrestriazl liring things four
alternative hypotheses can be advanced:
1) Living things essentially identice.. to those found on
earth exist on the planets (Mars « Venus). -

2) Living things similar in their ¢css metabolic aspects
to terrestrial forms exist, Tis is to say that processes
such as fermentation, respirai.cn, or photosynthesia occur.
Interesting and important dif/erences in the details of
the processes and of the living things associated with
them may occur,

3) Living forms exist basically different from terrestrial
ones, possibly even basec on a non-carbon chemistry.

hh) There is some form of "roto-life" either extensive or
perhaps marginal,

5) The planets are completely sterile; in other words, the
physical chemical mke-up of the planets has not led to
the formation of any self-replicating molecular pattern.

6) Allied to this is the possibility that a presently sterile
planet may harbor ‘the remains of an earlier population of
living things.
Lie veby great inpoertanes of “ypovheses (3) anc (1)
Should be empl:cized, If either situation occurs one can hope to make
observations «. biogenesis,

C. GENERAL AF ROACH TO THE PROBLEM

The methods of getting information seem to fall into
four groups:

1) Observations of the planets from the earth or fron
a near-earth satellite or balloon.

2) Observations of the planets from planetary probes
or satellites.

3) Landings on the planets.

Experiments and observations on earth will be required
both to perfect methods and instruments and to learn how to interpret the
observations on other planets.

These approaches require transmission of information.
The tranenission is simplest when it is merely an answer to a 'yes-or=no!
question, the cuestion itself may be complex. Hence. the study of specific
communication problems will have to follow the formulation of significant
biological questions.

D. DANGERS AND CAUTIONS

Some of the approaches mentioned above entail a certain
danger of disturbing the system under observation; the danger increases in
proportion to the nearmess to the system: thus (3) is much more dangerous
than (2).

Not only mst the obvious sources of contamination
(bacteria and bacterial Spores) be eliminated, but also the more subtle
sources, such as dead bacteria and organic matter of any sort. It is essen-~
tial to avoid unnecessary or thoughtless contamination. The only certain
way of avoiding contamination wuld be not to approach the planets at all;
this is obviously inadmissible. The best solution, therefore, is to have
in advance a clear plan of attack on the problem. Thus all the cbservations
which may reasonably be expected to bé useful should be made by the leest
dangerous approach, before a more dangerous observation is attempted,
Whenever an observation is made where there is danger of contamination, care
should be taken to obtain the maximum of information at once and to remove
the possible source of contamination as soon as possible.

E. TYPES OF INFORMATION “HICH MAY BE USEFUL

Many suggestions for possible observations were made.
A brief summary of these follows together with some remarks concerning our
present knowledge. Most of: the suggestions implied a belief in the probability

of hypotheses (1) or (2).

[. Present Information: (See Science, Vol. 128, page 89)
a) Temperature
(1) The temperature on Mars varies from about 300°K

to 150°K; the maximum is certainly adequate for
life and indeed is probably adecuate for the
marginal proliferation of known bacterial forms.

(2) Venus (at the surface) is much hotter: 600° (?)
b) Atmosphere

(1)

(2)

The total mass of the etmosphere of Mars is un-
known, There is a large abundance of CO,. Ice

is known to present ‘on the polar caps. Water

vapor in the atmosphere is not much more than
necessary to account for this. The spectroscopic
evidence is consistent with the seasonal transport
of this water from pole to pole via the atmosphere.
No evidence for oxygen exists (oxygen could be 1%
of the concentration in the terrestrial atmosphere),
Nitrogen hes not been detected, but could be present
in large amounts.

Venus has a heavy concentration of CO,. Nothing

is known about other gases. Clouds permanently
obscure the surface,
c) Mapnetic Field

(1) If Mars has a core, this must be small, there-
fore the magnetic field of Mars is likely to
be weak, or perhaps zero. This, coupled with
the low density of the atmosphere, leads to
the presumption thet the surface is very heavily
irradiated with high-energy particles (as well
as with intense UV).

(2) Venus has a mass and density similar to that
of the Earth. Therefore the internal structure
and magnetic field may be similar.

d) Direct evidence of life and/or organic material

(1) For Mars there is the behavior (seasonal waxing
and waning). of the ‘dark patches', as contrasted
with ‘desert areas", Moreover, there is the
spectroscopic evidence of Sinton showing the
existence of a 3.h6 absorption band associated
with the dark petches. This bend is charscteristic
of C-H bonds in compounds heavier than methane.
Its presence makes very probable the existence of
organic matter oh Mars, but does not imply the
presence of ‘living forms. It may indicate the
existence of a “Miller-process" on a massive ‘scale,
Doty here raised the problem of the destruction
of organic matter by UV-radiation. It is possible
that a steady state concentration of organic
material might occurs the possibility of a layer-
ing of the formed material and protection of the
lower layers was mentioned.

(2) For Venus there is no information available.
/s/

II. Information Needed to Formulate Pertinent Questions

(a) More data én organic syrithesis from inorganic
compounds including models of planetary atmoephere,
and studies on layering effects.

(b) Study of life correlates in the atmosphere and on
the surface of the earth, and of their possible
detection from.an earth's satellite.

III, Information from Balloon: and Terrestrial Satellites

Spectroscopic analysis of planetary »tmospheres and
ani surfaces. Especially important are oxygen, nitrogen, and trace constit-
vents, Also, a refinement of Sinton's observations on the 3.)6p band will
be possible, and an extension of these observations into the visible spectrum,
with special reference to chlorophyll.

IV. Information from Planetary. Probes and Satellites
a) Photographic observations
b) Spectroscopic experiments such as mentioned under
III, with the possibility of observing small regions.

c) Radar observations to determine the "roughness" of
the planetary surface. On the earth the "roughness"
is almost entirely due to vegetation.

a) Observations of free radicals, More information on
feasibility and reliability of such observations is
needed,

e) Chemical analysis from a probe entering the atmosphere
or with instruments landing on the planetary surface,
Particulerly important wovld be the observation of
optical activity.

F. LIMITATIONS OF -PRESENT CONCEPTS OF LIFE

It is obvious thet in order to arrive at an idea of the
“inds of observations that would be most useful to make from planetary satellites
(or even more by landings) much. more thought mist be given to the properties to
be expected from the possible forms of living things. What, for example, are
the kinds of energy metabolisms possible}; what kind of activity might be associated
with proto-life?