188 Encyclopedia of the Solar System
detecting life on planets or satellites, both the intelligent and
primitive varieties, if it exists in abundance on the surface.
On the other hand, if there is life on a planet or satellite that
does not have a strong signature on the surface, as would
probably be the case if Europa or Ganymede harbor life,
then a flyby mission may not be adequate to decide the
question. With regard to abundant surface life, we have a
positive result for Earth and a negative result for every other
body in the solar system.
7. Conclusions
Viewing Earth as a planet is the most important change
of consciousness that has emerged from the space age. De-
tailed exploration of the solar system has revealed its beauty,
but it has also shown that the home planet has no special
immunity to the powerful forces that continue to shape the
solar system. The ability to remotely sense Earth’s dynamic
atmosphere, oceans, biosphere, and geology has grown up
alongside our ever-expanding ability to explore distant plan-
etary bodies. Everything we have learned about other plan-
ets influences how we view Earth. Comparative planetology
has proven in practice to be a powerful tool for studying
Earth’s atmosphere and oceans. The lion’s share of under-
standing still awaits us, and in its quest we continue to be
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