Faith in Beagle 2? What faith? It does seem to carry the right scientific instruments to look for biosignatures. Twill be a sad day for you if the little Beagle finds evidence for life eh? No more playing Mr. Mars...people will be informed and Mars will be more important than a place to plant flags and footprints.

Adv. Space Res. Vol. 30, No. 6, pp. 1593-1600, 2002

MARTIAN METEORITES DO NOT ELIMINATE THE NEED FOR BACK CONTAMINATION PRECAUTIONS ON SAMPLE RETURN MISSIONS

Benton C. Clark

Lockheed Martin Astronautics, POB 179, MS 5-8000, Denver, CO 80201, USA

ABSTRACT
The phenomenon of natural transport of material from the surface of Mars to the surface of planet Earth,
in the form of martian meteorites, cannot be used as justification to relax or abolish plans and procedures
for quarantine and strict sample containment for future Mars sample return missions (MSR). Biosphere
upsets, ecological disasters, and species extinctions have been far too numerous and their causes too
poorly understood to rule out occasional possible contributions from exogenous biological invaders. In
addition, in today's large, highly intertwined global civilizations, even small perturbations to public
health, ecological stability, economic balances, or perceived threat of any of these could eclipse the public
support that will be needed for space exploration and sample return programs with responsible planetary
protection measures. © 2002 COSPAR. Published by Elsevier Science Ltd. All rights reserved.
INTRODUCTION
A concern with respect to return of samples from Mars has been the possibility, no matter how remote,
that martian life forms could in some way be damaging or dangerous to planet Earth. However, the
potential hazard modalities of an uncontrolled life form are many: infectious agents with medical conse-
quences to humans or other important life forms, ecological prodigies that displace current species, or nui-
sance organisms whose proliferation as pests would be unpalatable and/or economically injurious. Al-
though the likelihood's are extremely low, these are not merely hypothetical possibilities. Clear-cut ex-
amples of each and every scenario abound, based upon the historical consequences of breakouts from
regional isolations in natural ecosystems. Recently, it has been suggested in print (Gladman and Burns,
1996; Gladman, 1997) and verbally by a variety of planetary scientists that the newly accepted reality that
martian material periodically ejected from Mars and finding its way to earth as meteorites is "evidence"
from which we might conclude that back contamination is of minor concern. This even has been
extrapolated by some that there should even be no concern at all (Zubrin, 2000), in contrast with the rec-
ommendations of a study sponsored by the U.S. National Academy of Sciences, which concluded al-
though the risk of contamination of Earth with significant impact is unlikely, the risk is not zero (p. 2,
NRC, 1997). In this paper, additional aspects of this problem are examined to show that sweeping judg-
mental conclusions that the risk can be assumed to be zero on the basis of the existence of martian
meteorites can be readily discredited on several grounds.

What hhs been called the "rain" of martian meteorites can hardly be called a flood. To date, only 0.1%
of the tens of thousands of meteorite specimens are identified as of martian origin. This is undoubtedly
too low for estimating the natural frequency of infall because of the bias against identification. Iron
meteorites are most common in collections, because they are the most bizarre and easiest to recognize as
different from typical terrestrial rocks. From the relative frequencies found in Antarctic and desert-plains
meteorites, where few natural terrestrial rocks are present, the lunar and martian meteorites undoubtedly
comprise a greater percentage of the infall.
None of the martian meteorites discovered to date are "fresh." All have been in space for between about
500 thousand and 20 million years as revealed by their cosmic ray exposure ages. The same rough scale
of antiquity holds even for a portion of the meteorites coming from our much nearer neighbor, the moon.
If martian organisms did arrive "recently", most of them took millions of years to get here. Except for the
case of organisms buried deep inside large boulders, it is clear that in such transfers, all organisms would
be exterminated by the lethal space environment. In a separate paper (Clark, 2001), the numerous barriers
to successful transfer of viable biological materials have been already delineated, with emphasis on certain
of the pertinent factors, such as the in-space radiation sterilization of samples and the improbability of
launch of materials which are most likely to be biologically-inhabited (e.g., sediments, aqueous materials,
etc.). It is often pointed out that a small but important fraction of meteorites could arrive here much, much
faster (Gladman, 1997; Mileikowsky et al., 2000)

CONCLUSIONS
Well-meaning but short-sighted statements by investigators and laymen, perhaps also seen as self-
serving, accept the risk of jeopardizing an already-eroded public confidence in science (Haerlin and Parr,
1999) and financial backing of space science and exploration. Although there is no indication of
significant organic compounds, biologically active entities, or toxicity hazards in the martian meteorites
discovered to date, these samples are too small in quantity or size to proxy as an "experiment" that tests
the hypothesis that no hazard exists. Responsible scientists and the scientific community need to take
these factors into account when discoursing on the relevance of martian meteorite experience to the
requirements for planetary protection.
ACKNOWLEDGEMENTS
The author gratefully acknowledges important comments by B. Gladman, and an anonymous reviewer.
REFERENCES
Cartwright, F. F. and M.D. Biddiss, Disease and History. Barnes and Noble Books (1991).
Clark, B. C. Planetary Interchange of Bioactive Materials: Probability Factors and Implications, Orig. of
Life and Evol. of Biosph., 31, 185-197 (2001).
Haerlin, B. and D. Parr. Nature, 400, 499 (1999).
Gladman, B. J. and J. A. Burns, Mars Meteorite Transfer: Simulation, Lett. to Ed., Science, 274, 161-2
(1996).
Gladman, B., Destination Earth: Martian Meteorite Delivery, Icarus 130, 228-246 (1997).
Hoyle, F. and N. C. Wickramasinghe. Comets - A Vehicle for Panspermia. Astrophys. and Space Sci.,
268 333-341 (1999).
Levine, A. J. Viruses. Scientific American Books Library (1992).
Mileikowsky, C., F.A. Cucinotta, J. W. Wilson, B. Gladman, G. Horneck, L. Lindegren, J. Melosh, H.
Rickman, M. Valtonen and J. Q. Zheng. Natural Transfer of Viable Microbes in Space, Icarus, 145,
391-427 (2000).
NRC, Space Studies Board of the National Research Council. Mars Sample Return: Issues and
Recommendations. National Academy Press, Washington, DC. (1997).
Ridley, Matt. The Future of Disease. Phoenix Orion Publishing Group (1997).
Stoddart, D. M. The Scented Ape. Cambridge University Press, Cambridge (1991).
Zimmer, C. Parasite Rex. Touchstone / Simon and Schuster (2001).
Zubrin, R. Contamination from Mars: No Threat, Planetary Report, 20/4, 4, (2000)