Microbiology and Immunology

Extraterrestrial microbiology WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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pounds. Again the results were equivocal, and may have indi-

cated microbiological activity. A third experiment that looked

for the presence of organic compounds in the soil was nega-

tive. In the final experiment, soil was examined using an

instrument called a gas chromatograph-mass spectrometer for

chemical signatures of biological activity. The test revealed a

great deal of water but little else.

These results have been the subject of debate, and have

not proven to be conclusive for the absence of microbiological

life. For example, at the time of the Vikingmissions, the full

extent of the diversity of microbiological life on Earth, specif-

ically the existence of living bacteria far below the surface in

regions where organic material was virtually absent, was not

known. With the discovery of archaebacteria, the possibility

that microbiological life could exist in the subsurface layers of

a planet like Mars has warranted a reassessment of the possi-

bility of Martian life. Furthermore, high resolution photo-

graphic surveys of the planet by orbiting probes in the 1990s

revealed geological features that are the same as dried rive val-

leys and floodplains on the Earth. These observations have

bolstered the view that Mars was once an abundantly moist

planet, capable of sustaining microbiological life.

To definitively address the issue of microbiological life

on Mars, the European Space Agency is scheduled to launch

the so-called Mars Express in June 2003. The mission will

have a two-fold purpose. An orbiting satellite will analyze the

planet from high altitude, while a surface probe will sample

the planet’s surface. The analytical equipment aboard the

Electron microscopic view of Martian meteorite showing bacteria-like forms.

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