precisely what comets transported through the Solar System during Earth’s
formation.
Rosetta was originally described as a mission “towards the origin of the Solar
System” and indeed that is certainly what it was. But, both since its inception and
following its execution, we have realised that comets will not give up these secrets
easily. On the other hand, it is worth remembering that the Rosetta data set is huge. A
colleague who is very familiar with one of the major instruments remarked to me that
he thought only 2–3% of the data from that instrument had really been explored
thoroughly more than 4 years after the completion of the mission. While I am not
quite so pessimistic about the data sets I myself am most familiar with, I would agree
that analysis of data sets could continue for many years both to extract the maximum
return from the investment made but also to prepare for the future. It is clear that
students can still now perform very worthwhile studies on the data sets and in
particular by linking observations from several instruments to exploit multiple
constraints.
One thing, however, has been obvious in compiling this work. The data sets we
have acquired, from all missions and observations, have limitations that should not
be swept under the carpet. This is, to some extent, a natural consequence of the
boundaries imposed when spacecraft missions are constructed and the limits on what
can be achieved by Earth-based remote sensing. But degeneracies cannot be ignored
and alternative explanations must be explored. In cometary science, there is plenty
left to do.
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9 Final Remarks