Chapter 9
Final Remarks
Two concepts have driven cometary science for much of the past 80 years. Firstly, if
comets really are debris from the formation of our Solar System then studying their
chemical and physical structure appears to be the only way to acquire data on the
processes occurring in our proto-planetary disc. The diversity now being seen in the
structures of other planetary systems suggests that every planetary system is “special”—the initial conditions make an enormous difference to the end result which
necessarily limits what we can learn from exoplanetary systems about our own.
Consequently, while we may be able to learn about processes from exoplanet
astronomy, the knowledge to be gained from our primitive objects has a major
role to play in constraining the specific processes and evolution of our own Solar
System.
The second reason for studies of comets has been their role in transporting
material (principally water and organics) across the Solar System. This is still the
subject of debate. Is the high D/H ratio observed at 67P indicating that Earth’s water
is not of cometary origin or are there other processes at work? At what stage in
Earth’s evolution did organic material become relevant and did comets contribute to
that reservoir? Was there a contribution to the evolution of life?
There remains insufficient information to constrain the theories associated with
these concepts. This is in part due to the facts that basic processes are not understood
and that details matter. We have only limited understanding of the processes
involved in proto-planetesimal formation. We have no understanding of whether
life can evolve from cometary material. We remain uncertain about the dynamical
history of our own Solar System over the past 4.6 billion years. One could go on.
While acquiring that information is challenging, comets do offer a laboratory for
testing hypotheses. It is apparent that to get at the chemical and physical structure
without ambiguity, we need to get “up close and personal” with these bodies. In
particular, the micro-structure of cometary material may provide us with clues to the
processes that were active during Solar System formation. Similarly, the chemical
compositions of the surfaces and interiors may provide better understanding of
© Springer Nature Switzerland AG 2020
N. Thomas, An Introduction to Comets, Astronomy and Astrophysics Library,
https://doi.org/10.1007/978-3-030-50574-5_9
447
Final Remarks
Two concepts have driven cometary science for much of the past 80 years. Firstly, if
comets really are debris from the formation of our Solar System then studying their
chemical and physical structure appears to be the only way to acquire data on the
processes occurring in our proto-planetary disc. The diversity now being seen in the
structures of other planetary systems suggests that every planetary system is “special”—the initial conditions make an enormous difference to the end result which
necessarily limits what we can learn from exoplanetary systems about our own.
Consequently, while we may be able to learn about processes from exoplanet
astronomy, the knowledge to be gained from our primitive objects has a major
role to play in constraining the specific processes and evolution of our own Solar
System.
The second reason for studies of comets has been their role in transporting
material (principally water and organics) across the Solar System. This is still the
subject of debate. Is the high D/H ratio observed at 67P indicating that Earth’s water
is not of cometary origin or are there other processes at work? At what stage in
Earth’s evolution did organic material become relevant and did comets contribute to
that reservoir? Was there a contribution to the evolution of life?
There remains insufficient information to constrain the theories associated with
these concepts. This is in part due to the facts that basic processes are not understood
and that details matter. We have only limited understanding of the processes
involved in proto-planetesimal formation. We have no understanding of whether
life can evolve from cometary material. We remain uncertain about the dynamical
history of our own Solar System over the past 4.6 billion years. One could go on.
While acquiring that information is challenging, comets do offer a laboratory for
testing hypotheses. It is apparent that to get at the chemical and physical structure
without ambiguity, we need to get “up close and personal” with these bodies. In
particular, the micro-structure of cometary material may provide us with clues to the
processes that were active during Solar System formation. Similarly, the chemical
compositions of the surfaces and interiors may provide better understanding of
© Springer Nature Switzerland AG 2020
N. Thomas, An Introduction to Comets, Astronomy and Astrophysics Library,
https://doi.org/10.1007/978-3-030-50574-5_9
447