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OCR for page 1
NATIONAL RESEARCH COUNCIL
COMMISSIOi\;ON PHYSICALSCIE;\;CES.~tATHE~tATICS.A:'\:DRESOURCES
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OFFICE LOCATIOS:
SPACESCIESCE 80AaD
IOUI'M HEsa.. II;ILDISC
::ST STaUT ASD
PESSSYLVASIA "\~S\:I, S '"
June 6~ 1985
Arnauld E. Nicogossian~ M.D.
Director~ Life Sciences Division
Code EBR
National Aeronautics and Space Administration
Washington~ D.C. 20545
Dear Arnauld:
In response to your letter requesting advice on categorization of the M~rs
Orbiter Mission~ from the point of view of planetary protection~ the Committee
on Planetary Biology and Chemical Evolution of the Space Science Board
considered this issue at its latest meeting on May15 and 16~ 1985.
For its deliberations~ the Convnittee 'solicited information and opinions
from a number of specialists~ all of whomare~ or have been involved in
studies related to this subject (I. Friedman~ Fla. State univ.; N. Horowitz~
Cal Tech; R. Huguenin~ University of Massachusetts; B. Jakosky~ Colorado U;
T. Jukes~ UC Berkeley; P. Mazur, ORNL; and C. Sagan~ Cornell). In addition~
the Committee was briefed by personnel of the MOproject~ who presented an
overview of themission~ with particular emphasis on the status of their
planning efforts to meet NASAls planetary protection guidelines.
In arriving at a reconvnended Category for this mission~ the Committee
strongly reaffirms the position~ taken by previous sse convnittees~ that Mars
is the prime extraterrestrial target for the study of planetary biology and
chemical evol~tion (cf.: Space Science Board~ "Opportunities and Choices
in Space Sciences~ 1974~II NAS1975~ Space Science Board~ IIPost-Viking
Biological Investigations of Marsll~ NAS1977). As a result of the Viking.
mission~ it appears that the likelihood of an indigenous biota on Mars is very
remote. Nonetheless~ the limited scope of the Viking investigations leaves
open the possibility that future studies may show this initial assessment to
be incorrect. Viking also raised a myriad of~ as yet~ unanswered Questions
-
regarding the chemical and physical environment of that planet Questions
such as the nature and distribution of the putative lIoxidantll imputed to be
present in the regolith~ and whether liquid water and/or organic compounds
exist at or near the surface of Mars in any regions of the planet.
The Committee is sensitive to the incompleteness of our understanding of
-
the Martian environment especially on the scale of IImicro-environments"
that might be adequate to sustain some potential terrestrial contaminants.
Furthermore~ we are mindful of the diversity and adaptive capabilities of
terrestrial microorganisms (of which only a fraction has~ as yet~ been
characterized~) These considerations~ together with our strong desire to
minimize the chances for ambiguity in future studies of Martian surface
samples dictated a conservative approach as the most prudent course to. follow
in connection with the MOcategorization.
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OCR for page 2
Arnauld E. Nicogossian, M.D.
June 6, 1985
Accordingly, the Committee judges the MO mission to be properly assigned a
Category III designation. Wefurther recommendthat the MOProject carry out
all of the precautions that the Project personnel described as being necessary
to meet the stringent requirements inherent in this category. These include:
assembly of the spacecraft in Class cleanrooms; biasing the injection
lOOK
aimpoint of the spacecraft to assure a probability of <10-5 of impact of the
launch vehicle, and a probability of <10-4 of impact of the spacecraft;
selecting a mapping orbit such that the probability of remaining in orbit
until the year 2009 is >0.9999; and, raising the orbit of the spacecraft upon
completion of the nominal mission to an orbit with a probability of >0.95 of
remaining stable until the year 2039.
With regard to the prospects of implementing these requirements, the
Committee is pleased to note the considerable effort that has already gone
into these matters on the part of the MOProject. Wetherefore expect that
meeting these planetary protection objectives will pose no insuperable
problems for them.
Please note that the Project personnel expressed a sense of urgency, since
their plans call for the "sign-off" on their final "Planetary Protection Plan"
in September of this year.
Finally, the Committee expressed its willingness and interest to assist
NASA categorizing additional solar system missions.
in In these cases, it
would seem most expedient to consider the issues involved for each proposed
-
mission at an earlier stage than was done for the MOmission that is, before
. concepts for the mission(s) become "hardened" and at a time when additional
requirements are less likely to be burdensome.
Yours sincerely,
? k~/:Ht
~eJ
Harold P. Klein, Chairman
Committee on Planetary Biology and
Chemical Evolution, SSB
cc: Or. Tom Donahue, SSB
