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by Michael Martin-Smith
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The Solar System enlarged 3 fold in ten years
For Astronautical Humanists seeking to extend the scope for our species' future, current trends in solar system exploration are opening up new practical challenges and possibilities. The Classical Age of space exploration - its first 40 years or so - has been concerned with exploration the main planets and moons of our solar system, mostly from the point of view of scientific academia in the fields of Astronomy and Geology. The principal objective has been to try to explain the origins and evolution of our solar system , how the planets came to be composed and located, and to see how Life fitted into this process.
Our amazing robot explorers-in flybys, orbiters, landers, and sample returns - have visited all but one ( Pluto) of the classical planets ,and most of the major moons known as points of light to our earthbound astronomers. The processes leading to the formation of our solar system and the likely conditions under which Life arose and developed are much better understood than only two generations ago, but it is clear that key stages in the accumulation of small particles into planetesimals and their coalescence into planets, and the formation of atmospheres and oceans is only partially understood, and we now believe that the hitherto relatively neglected small bodies such as the Comets and Asteroids hold many of the remaining pieces of the jigsaw.
In the past 10 years key features of our story have been altered beyond recognition. Before 1994-5 the idea that we should ever actually detect planets in orbit around other stars was a theoretician's dream considered by many to be forever beyond our reach. In 10 short years we have found 150 other solar systems, which are causing us to revisit our ideas of planetary birth. In this same period our own solar system has been enlarged at least 3 fold, with the discovery of large planetoids up to three times further from us that Pluto; indeed Pluto is now regarded as the "ambassador" of a whole new class of objects -neither typical planets nor yet asteroids or comets -from which our system was probably assembled in its first 50-100 million years.
As if this were not enough, we find comets that behave like asteroids, from exhaustion of their surface ices, and asteroids in elliptical comet-like orbits beyond their normal habitat between Mars and Jupiter- out to the reaches of Saturn and Uranus. Asteroids that regularly cross the orbit of Earth have been found while comets have been seen to break up and shift their orbits in a historical instant.
