Exob. 8-8
10/24/60

CONMENTS QQ. AND PROPOSALS FOR THE MARS 1964 EXPERIMENT

1. A lander should be attempted. Physical and chemical measurements should

take priority within the limited capacity of the instruments and telemetry channel.
These should aim at characterizing the surface environment and would greatly
enhance the precision of later flights.

2. These measurements should include:

a) composition of the atmosphere, especially 0, and H,0
b) diurnal temperature cycle at ground level (a high middle latitude
might offer the most promising site for moderate temperatures)

c) if more prolonged measurements, the seasonal temperature cycle at
ground level

d) ground moisture (electric conductivity?)

e) pH and concentration of soluble electrolytes (electrical conductivity)
of soil samples suspended in water

f) detection of pyrolyzable organic matter in soil sample - if weight
permitted, even better to have gas chromatogram and mass spectra

g) the solar spectrum at ground level

3. Multivator. {f weight permits, and with higher priority, if there is any
doubt as to the effectiveness of sterilization controls, a simple multiple |
chamber culture device can be constructed. About 20 chambers containing 1 m}

of culture fluid each can be flown sealed, opened for, inoculation, resealed |

and scanned once daily for several weeks by nephelometer and mhometer. This
experiment should be possible within 10, perhaps 2=5 pounds, and need take

only a few dozen bits per day. The same design could also be used for the
detection of gross enzymatic activity in soil samples collected by the inhalation
of atmospheric dust.

The detailed composition of the culture media has not yet been thought out.
Some general possibilities can be indicated in the light of the limited
avaitable information on the habitat. The mechanism of carbon fixation is likely
to be less predictable than the oxidation of reduced carbon; some organisms |
should be found working the latter part of the cycle and these are stressed in
the indicated tests.

a) Electron acceptors = these might be furnished either in solution
or in a coherent pellet

 

 

 

 

 

Fe,0, > Fed, Fe
5 > S$

NO, > Ny

No > NHS

$0), > §

 

0 +H (as might be furnished by slow electrolysis) > Hod
b) Sources of reduced carbon

CH,0 CHCHO CH,COCOOH

0 _ - -
CH, H CH.0H D= and L CH,CHNH,, COOH
CH.NH,, CoHNH, CHNH,,COOH
HCOOH CH,COOH CH,OHCOCH,OH
co CH,NH,,COOH CHOHCHOHCH,OH
Cc CHOCOOH

COOHCOOH
a COOH en
he cH, cH,
He CHOH CHNH,,
COOH COOH COOH
De and L-

D- and L=:. glucose; deoxyribose; ribose; amino acid mix 2
than C53 purines and pyrimidines.

c) The fermentation (internal redox dismutation) of the organic compounds
in middle oxidation states can be tested without specifying the oxidant.

d) Qpen questions: pH, ionic strength, phosphate, trace metals and growth
factors, residual oxygen

e) We are planning to look into the question of overt enzymatic activity
of ¢rude soils. This approach would be more plausible if we could plan
to fractionate the organic particles by flotation for making an enzymatic
test - e.g. for diaphorase or ATPase...

J. Lederberg