help understand the basic physical processes and to try to establish (possibly
empirical) relationships between variables.
It is also apparent from the surface morphology of 67P and the variations in
activity (both in magnitude and composition) with position that inhomogeneities in
longitude and latitude on the nucleus are present. The variability evident at 9P/
Tempel 1 was perhaps less extreme but nonetheless present. There remains considerable doubt whether this inhomogeneity is primordial or evolutionary. Hence
comparisons of areas of different morphology and/or morphological context are
highly desirable.
The results obtained by the CONSERT radar on Rosetta demonstrated the unique
capability of radars to provide information about the internal structure of a comet
nucleus. However, this instrument was operated under unfavorable conditions
resulting in considerable uncertainty about the deep interior. A follow-up ground
penetrating radar would clearly be an interesting examination of theories on nucleus
formation.
The isotopic, elemental, chemical, and chiral composition of non-volatile material, including complex organic material was not established. The elemental composition of ejected dust was found with COSIMA but the composition of complex
organics, for example, remains unknown. Clearly, any discussion of comets bringing
complex organics to the inner solar system and their participation in the evolution of
life requires knowledge of the composition of these organics and it is fully apparent
that the optimum way to address composition is by using the power of Earth-based
analytical laboratories. Remote-sensing approaches are totally inadequate whereas in
situ analysis remains technically challenging and limited by spacecraft resources. It
is this aspect that forms the strongest argument for initiating a sample return mission
to a comet although the Stardust mission has scratched the surface of this particular
topic.
Given the difficulties of executing such investigations, the answers will not be
available any time soon. Nevertheless, analytically, we are in a far better position
now than 20 years ago with recent decades having seen both progressive increases in
performance of instrumentation, huge increases in computer power and ease of use,
and breakthroughs such as the introduction of nano-SIMS technology, the spread of
con-focal microscopy and sub-micron resolution X-ray microscopes as well as the
greater availability of synchrotron-based techniques.
Laboratory analysis (especially of the mineralogy, chemistry and isotopic composition) of solar-system and extra-solar material has been enormously important in
furthering our understanding of the origin and evolution of the solar system, as well
as shedding light on the nucleosynthetic processes in several types of star. Using
samples returned from the Moon, as well as meteorites likely to have come from a
variety of parent bodies (including Mars and perhaps the asteroid Vesta), we have
been able to determine the age of the Earth and the solar system, the timescales for
the dynamic evolution of the solar system, and the timescale over which liquid water
existed on early planetesimals. The power of laboratory instrumentation, and the
advantage of having samples on Earth, is shown by the way in which lunar samples
returned almost 50 years ago are still leading to fresh insights. If we had instead
8 Future Investigations of Comets
441
empirical) relationships between variables.
It is also apparent from the surface morphology of 67P and the variations in
activity (both in magnitude and composition) with position that inhomogeneities in
longitude and latitude on the nucleus are present. The variability evident at 9P/
Tempel 1 was perhaps less extreme but nonetheless present. There remains considerable doubt whether this inhomogeneity is primordial or evolutionary. Hence
comparisons of areas of different morphology and/or morphological context are
highly desirable.
The results obtained by the CONSERT radar on Rosetta demonstrated the unique
capability of radars to provide information about the internal structure of a comet
nucleus. However, this instrument was operated under unfavorable conditions
resulting in considerable uncertainty about the deep interior. A follow-up ground
penetrating radar would clearly be an interesting examination of theories on nucleus
formation.
The isotopic, elemental, chemical, and chiral composition of non-volatile material, including complex organic material was not established. The elemental composition of ejected dust was found with COSIMA but the composition of complex
organics, for example, remains unknown. Clearly, any discussion of comets bringing
complex organics to the inner solar system and their participation in the evolution of
life requires knowledge of the composition of these organics and it is fully apparent
that the optimum way to address composition is by using the power of Earth-based
analytical laboratories. Remote-sensing approaches are totally inadequate whereas in
situ analysis remains technically challenging and limited by spacecraft resources. It
is this aspect that forms the strongest argument for initiating a sample return mission
to a comet although the Stardust mission has scratched the surface of this particular
topic.
Given the difficulties of executing such investigations, the answers will not be
available any time soon. Nevertheless, analytically, we are in a far better position
now than 20 years ago with recent decades having seen both progressive increases in
performance of instrumentation, huge increases in computer power and ease of use,
and breakthroughs such as the introduction of nano-SIMS technology, the spread of
con-focal microscopy and sub-micron resolution X-ray microscopes as well as the
greater availability of synchrotron-based techniques.
Laboratory analysis (especially of the mineralogy, chemistry and isotopic composition) of solar-system and extra-solar material has been enormously important in
furthering our understanding of the origin and evolution of the solar system, as well
as shedding light on the nucleosynthetic processes in several types of star. Using
samples returned from the Moon, as well as meteorites likely to have come from a
variety of parent bodies (including Mars and perhaps the asteroid Vesta), we have
been able to determine the age of the Earth and the solar system, the timescales for
the dynamic evolution of the solar system, and the timescale over which liquid water
existed on early planetesimals. The power of laboratory instrumentation, and the
advantage of having samples on Earth, is shown by the way in which lunar samples
returned almost 50 years ago are still leading to fresh insights. If we had instead
8 Future Investigations of Comets
441