The initial aim of this project was to develop a non-contact fibre optic based displacement sensor to operate in the harsh
environment of a 'Light Gas Gun' (LGG), which can 'fire' small particles at velocities ranging from 1-8.4 km/s. The
LGG is used extensively for research in aerospace to analyze the effects of high speed impacts on materials. Ideally the
measurement should be made close to the centre of the impact to minimise corruption of the data from edge effects and
survive the impact. A further requirement is that it should operate at a stand-off distance of ~ 8cm. For these reasons we
chose to develop a pseudo con-focal intensity sensor, which demonstrated resolution comparable with conventional
PVDF sensors combined with high survivability and low cost. A second sensor was developed based on 'Fibre Bragg
Gratings' (FBG) which although requiring contact with the target the low weight and very small contact area had
minimal effect on the dynamics of the target. The FBG was mounted either on the surface of the target or tangentially
between a fixed location. The output signals from the FBG were interrogated in time by a new method. Measurements
were made on composite and aluminium plates in the LGG and on low speed drop tests. The particle momentum for the
drop tests was chosen to be similar to that of the particles used in the LGG.
The NASA Stardust mission to comet 81P/Wild-2 returned to Earth in January 2006 carrying captured cometary dust
grains. Analysis of these grains is permitting an extensive study of cometary composition to be carried out. This includes
identifying both the mineral and organic content of the captured material. Based on this, the picture emerges of a comet
whose component materials have a diverse origin and which has not undergone any extensive aqueous alteration, has a
nitrogen rich organic history, may contain amines and at least 1 amino acid and has organics which in some respects
resemble interplanetary dust particles and meteorites, in others resemble one and not the other, and in yet others are
distinct from both. In terms of astrobiology, comets as a source of organic materials for the inner Solar System clearly
have a role to play, but this cannot be fully assessed based on the history of just one comet nucleus. Nevertheless, the
positive identification of a range of organic materials in this comet significantly moves forward the discussion of organic
materials and comets.
An analysis is carried out of the survival fraction of micro-organisms exposed to extreme shock pressures. A variety of
data sources are used in this analysis. The key findings are that survival depends on the behaviour of the cell wall. Below
a critical shock pressure there is a relatively slow fall in survival fraction as shock pressures increase. Above the critical
threshold survival starts to fall rapidly as shock pressure increases further. The critical shock pressures found here are in
the range 2.4 to 20 GPa, and vary not only from organism to organism, but also depend on the growth stage of given
organisms, with starved (i.e., no growth) states favoured for survival. At the shock pressures typical of those involved in
interplanetary transfer of rocky materials, the survival fractions are found to be small but finite. This lends credence to
the idea of Panspermia, i.e. life may naturally migrate through space. Thus for example, Martian meteorites should not a
prior be considered as sterile due to the shock processes they have undergone, but their lack of viable micro-organisms
either reflects no such life being present at the source at the time of departure or the influence of other hazardous
processes such as radiation in space or heating of surfaces during entry into a planetary atmosphere.
Conference Committee Involvement (5)
Instruments, Methods, and Missions for Astrobiology XVI
27 August 2013 | San Diego, California, United States
Instruments, Methods, and Missions for Astrobiology XIV
23 August 2011 | San Diego, California, United States
Instruments, Methods, and Missions for Astrobiology XII
4 August 2009 | San Diego, California, United States
Instruments, Methods, and Missions for Astrobiology XI
12 August 2008 | San Diego, California, United States
Instruments, Methods, and Missions for Astrobiology X
28 August 2007 | San Diego, California, United States
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