Mars is a neighboring planet that has intrigued us for hundreds of years. It offers the
possibility that we will find another world where life might have begun. Observations of
Mars with telescopes in the early 1900s indicated that perhaps Mars and Earth were very
similar. In fact, the suggestion was made that Mars may have been an older version of
Earth--perhaps a civilization had been present and was now dying.
One of the questions we had when we sent our first spacecraft was exactly how similar is
Mars. Our surprise has been in how different the two planets are. We believe Mars was
once a wet, warm world. Perhaps with streams, lakes pooling, perhaps even oceans. And
at this time perhaps, there were the conditions necessary for life to begin.
Since that time, the 3-4 billion years that have past have seen an enormous change in its
climate. Today, Mars is an arid world, it's the thin atmosphere, it's devoid of any
evidence of life on its surface. Whether there was life there or not we don't know. But
what we can say is that there's plenty of evidence that water was once present on the
surface.
Our earlier missions, the Viking landers and its orbiters, gave us an initial view of the
planet. But now with MGS [Mars Global Surveyor], we have a view of the topography of the planet, we have an
understanding of the circulation of its atmosphere, and we have an understanding of the
way in which water may have coursed over its surface in the distant past.
At every turn, our questions seem to bring about more questions. We had expected to see
minerals, minerals that could only be formed in the presence of water, and that those
minerals would be at the mouths of the channels where we see that water must have
moved. But we don't see those minerals. And so our surprises are as much as what we
have not seen as in the discoveries of things unknown.
Mars Odyssey is a mission that takes a step in a trail that we outlined almost 20 years ago
to determine exactly where the environments might have been suitable for the origins of
life. If we find those environments with the Mars Odyssey, we are going to go to those
locations, we're going to set down rovers, landers, do surface examinations and perhaps
return samples from those sites.
