Earlier research has sought to utilize the exceptional thermal conductivity of CNTs to produce a heat spreader by bulk cross-linking the CNTs into an interpenetrating network. An isotropic thermal conductivity of 2150 W/m-K was measured in a 5 μm thick MWCNT film which had been subject to argon ion bombardment with an ion energy of 4 keV and a fluence on the order of 10<sup>17</sup> ions/cm<sup>2</sup> . While energetic ions will randomly bombard the entire CNT network, on occasion, one will strike a junction where two or more CNTs are touching, momentarily disrupting them. CNTs have the remarkable ability to self-heal, and in doing so, the disrupted junction self-heals into a new interpenetrating junction. However, practical heat spreader applications require films at least 100 times thicker than this initial demonstration. To achieve this, substantially higher ion energies and fluence were applied. But rather than forming interpenetrating junctions deeper into the bulk of a CNT thick film, an interesting new form of high aspect ratio structure results, where groups of CNTs are now vertically aligned, even though the original CNT thick film was randomly oriented. There is also a sharp transition at the base of these structures from the new aligned form to the original randomly oriented form. We consider various aspects of ion-induced sputter dynamics coupled to the growth processes of CNTs to account for these new aligned high aspect ratio structures. The role of ion channeling within and between CNTs is also considered.
Isolated individual carbon nanotubes (CNTs) have shown exceptional thermal conductivity along their axis, but have
poor thermal transfer between adjacent CNTs. Thick bundles of aligned CNTs have been used as heat pipes, but the
thermal input and output areas are the same, providing no heat spreading effect. Energetic argon ion beams are used to
join, or cross-link overlapping CNTs in a thick film to form an interpenetrating network with an isotropic thermal
conductivity of 2150 W/m-K. Such thick films may be used as heat spreaders to enlarge the thermal footprint of various
electronic and semiconductor devices, laser diodes and CPU chips, for example, to enhance cooling.
Cosmologists refer to elements heavier than helium as “metals” and are essential as the building blocks of life, as well as the formation of rocky, terrestrial, Earth-like planets on which life is likely to be found. Widely-accepted cosmological models suggest the early universe was extremely metal-poor, limiting opportunities for life to arise. With the formation of galaxies and on-going stellar synthesis of heavy elements, these opportunities continue to improve. We consider the Galactic Habitable Zone of our Milky Way galaxy, how it may have appeared in the past, and how it may evolve over time, increasing the likelihood of the formation of rocky Earth-like planets, and the opportunities for life to emerge on them.
While life on Earth continues to be discovered in unlikely environments, the underlying biochemistry is all very similar, based on the element carbon, and requiring liquid water. We consider alternate biochemistries based on elements other than carbon, including other group IVA elements, such as silicon and germanium, and solvents other than water. Terminal electron acceptors other than oxygen are also discussed. A fundamental issue is raised related to the detection of, and even the definition of life, whether it is carbon or non-carbon based. An extreme example of this issue would be in consideration of speculative life based on electrically charged dusty plasmas, which may have no physical body.
The rapidly accelerating rate of discovery of exoplanets has been dubbed the “golden age of discovery” of these planets,
with an increasing number approaching Earth-like terrestrial planets, in habitable zones. Improving capability of both
ground-based and space-based instrumentation permits the examination of a given exoplanet’s transmission and
reflectance spectra that may hold clues to a habitable environment, and possibly, an indication of extraterrestrial life. To
provide a context for assessing these clues, we consider how Earth would have appeared to an observer at interstellar
distances, and how this appearance would have changed from shortly after its formation, to the present.
The generally accepted notion of a single origin of life from a primordial soup on the early Earth has been challenged recently by the suggestion of a “second life,” “shadow life,” and even “biological dark matter.” The problem in classifying these microorganisms is in the difficulty or complete failure of the 16s genetic fingerprinting process, suggesting a different underlying biochemistry resulting from at least a second origin of life. We consider an extension of this concept to include continuous origination of life throughout Earth’s history, up to the present. The consequences for interpreting the “tree of life” are also considered.
Over 500 exoplanets have been discovered so far, some being rocky, terrestrial planets. Advancing instrumentation
permits spectroscopic examination of their atmospheres, and remote detection of potential of biogenic gases. Of
particular interest are oxygen and methane, although other gases are considered. Short residence time of these gases
implies continued renewal. Abiotic sources are considered at levels that could be misinterpreted as a pseudobiosignature.
Photodissociation of water molecules, for example, could produce an oxygen pseudo-biosignature,
although generally at low levels. However, large-scale water loss events, as are thought to have occurred on Venus and
Mars, could produce a substantial pseudo-biosignature.
The Drake Equation was originally composed as an attempt to quantify the potential number of extraterrestrial
civilizations in our Galaxy which we might be able to detect using a radio telescope. Since this equation was first
formulated, nearly 50 years ago, we have discovered that life on Earth arose very early in its history, and has filled
virtually every habitable, potentially extreme, niche available. This suggests that simple forms of life might be plentiful
where possible, and can be observed remotely by atmospheric biosignatures in the host planet. We consider
modifications to the Drake Equation to reflect this new understanding.
Microorganisms may exist in Low Earth Orbit both from terrestrial sources, and potentially, from extraterrestrial
origins. A simple, low cost method for in-situ detection is proposed, suitable for CubeSat and similar micro and
nano-satellite implementation. A block of silica aerogel, similar to that used on the highly successful Stardust
mission, is used as a collection medium. Edge-wise UV illumination by a LED array, and orthogonal optical
emission detection by a photodetector array, is used for identification. The detection process is on-going, and no
sample return is required. Potential terrestrial background sources and missions of extraterrestrial opportunity are
The detection of extraterrestrial life in-situ assumes that a positive indication is the result of an indigenous life form, and
not the result of forward contamination from Earth. Atmospheric discharge cold plasma jets have proven effective in the
decontamination of a wide range of microorganisms, including Deinococcus radiodurans, through multiple modes of
action, yet the effect is relatively gentle on surfaces being decontaminated. An individual plasma jet may have a beam
diameter of only a few millimeters, requiring extensive decontamination time for a given surface area. Techniques are
discussed for assembling large area multi-jet arrays, and their mechanisms of decontamination. Application to back
contamination in sample return missions is also considered.
Multi-robotics places a potentially large number of independent robotic agents in a given situation where they may
interact cooperatively toward a common task. However, by having each of these robotic agents essentially identical, the
overall scope of their mission is limited. By fractionating their capabilities with varying degrees of specialization in a
hierarchical fashion, the mission capability can be greatly expanded. Test prototype examples are discussed of a large
carrier robotic vehicle containing several smaller specialized robotic vehicles, all teleoperated, which can interact
cooperatively, both sequentially and in parallel toward a common task.
Arrays of atmospheric discharge cold plasma jets have been used to decontaminate surfaces of a wide range of
microorganisms quickly, yet not damage that surface. Its effectiveness in decomposing simulated chemical warfare
agents has also been demonstrated, and may also find use in assisting in the cleanup of radiological weapons. Large area
jet arrays, with short dwell times, are necessary for practical applications. Realistic situations will also require jet arrays
that are flexible to adapt to contoured or irregular surfaces. Various large area jet array prototypes, both planar and
flexible, are described, as is the application to atmospheric decontamination.
The pale featureless cloud tops of Venus reveal a rich complexity when viewed in ultraviolet. These features result from
an unknown absorber brought up from lower atmospheric levels by convection, particularly at lower latitudes. While the
surface of Venus is extremely hostile to life as we know it, there exists a habitable region in the atmosphere, centered at
approximately 50 km, where the temperature ranges from 30 to 80ºC and the pressure is one bar. Numerous examples of
cloud-borne life exist on Earth. However, the environment in the Venus atmospheric habitable zone has only a few ppm
of water which is present as misty droplets, strong sulfuric acid, and intense UV illumination. The proposal that putative
cloud-borne life forms in Venus' atmospheric habitable zone can be transported to Earth by a solar conveyance face
several challenges. Vigorous convective mixing, especially at the lower latitudes is considered as a means of transport to
the upper reaches of Venus' atmosphere. Potential propulsive forces imparted by both solar wind and sunlight pressure
are considered as a means of achieving escape velocity from Venus. Additional hurdles include direct exposure by such
transported life forms to the rigors of the space environment. These are contrasted to those experienced by
microorganisms that may be carried within meteorites and comets. A middle ground is perhaps demonstrated by
plankton that has been observed at high altitudes on Earth, likely lofted there by a hurricane, which is encased in
protective ice crystals.
In the almost half century since the Drake Equation was first conceived, a number of profound discoveries have been
made that require each of the seven variables of this equation to be reconsidered. The discovery of hydrothermal vents
on the ocean floor, for example, as well as the ever-increasing extreme conditions in which life is found on Earth,
suggest a much wider range of possible extraterrestrial habitats. The growing consensus that life originated very early in
Earth's history also supports this suggestion. The discovery of exoplanets with a wide range of host star types, and
attendant habitable zones, suggests that life may be possible in planetary systems with stars quite unlike our Sun. Stellar
evolution also plays an important part in that habitable zones are mobile. The increasing brightness of our Sun over the
next few billion years, will place the Earth well outside the present habitable zone, but will then encompass Mars, giving
rise to the notion that some Drake Equation variables, such as the fraction of planets on which life emerges, may have
Atmospheric discharge cold plasmas have been shown to be effective in the reduction of pathogenic bacteria and spores
and in the decontamination of simulated chemical warfare agents, without the generation of toxic or harmful by-products.
Cold plasmas may also be useful in assisting cleanup of radiological "dirty bombs." For practical applications
in realistic scenarios, the plasma applicator must have both a large area of coverage, and a reasonably short dwell time.
However, the literature contains a wide range of reported dwell times, from a few seconds to several minutes, needed to
achieve a given level of reduction. This is largely due to different experimental conditions, and especially, different
methods of generating the decontaminating plasma. We consider these different approaches and attempt to draw
equivalencies among them, and use this to develop requirements for a practical, field-deployable plasma
decontamination system. A plasma applicator with 12 square inches area and integral high voltage, high frequency
generator is described.
A number of photosynthetic systems have evolved on Earth to harvest various portions of the available spectrum from its
G2 star. Currently, the number of confirmed extrasolar planets approaches 300, although many are in orbits well outside
their habitable zone. This largely results from an observational bias that tends to more easily spot these "hot Jupiters,"
but increasingly more Earth-like extrasolar planets are detected. The spectral classes of the stars supporting these planets
are generally well-identified, permitting some basic assumptions on the inner and outer habitable zone radii. We can also
make some assumptions on the spectrum of photon energy available for potential photosynthesis on these planets,
allowing for local atmospheric effects. The absorption spectra of terrestrial photosynthetic systems, both naturally
evolved, and artificially created, are matched to the anticipated spectra on extrasolar planets. Further consideration is
given to the cooler M class stars, whose large number and long life enhance the likelihood of photosynthesis evolving.
Cold plasma applicators have been used in the Medical community for several years for uses ranging from hemostasis
("stop bleeding") to tumor removal. An added benefit of this technology is enhanced wound healing by the destruction of
infectious microbial agents without damaging healthy tissue. The beam is typically one millimeter to less than a
centimeter in diameter. This technology has been adapted and expanded to large area applicators of potentially a square
meter or more. Decontamination applications include both biological and chemical agents, and assisting in the removal
of radiological agents, with minimal or no damage to the contaminated substrate material. Linear and planar multiemitter
array plasma applicator design and operation is discussed.
Often, micromorphologies, interpreted as microfossils, provide the first clues to exciting and potentially
controversial discoveries related to the early origins of life on the Earth, as well as the potential for life on other
planets. It has been said, however, that exceptional claims require exceptional proof, and micromorphological
evidence alone may have several possible interpretations, both biotic and abiotic. Garcia-Ruiz, et al. (2003) have
shown how silica-coated carbonate crystals in a chert-like matrix can self-assemble inorganically into long folded or
braided filaments that closely resemble cyanobacteria fossils thought to be 3.5 billion years old. Recent advances in
the field of Materials Science provide numerous other examples ofmicromorphologies that, due to their complexity
and structure, might be misinterpreted as microfossils despite their clearly abiotic origin. Several examples will be
discussed. While the chemistries ofthese abiotic micromorphologies could be considered rather exotic and therefore
discounted, the same fossilization process that operates on biotic microorganisms could operate here as well.
The Mars Exploration Rovers (MER) Sojourner in 1997, and Spirit and Opportunity in 2004, provide an example of how the selection of rover size impacts the nature of their respective mission objectives and capabilities. Smaller rovers tend to be more nimble and can more closely explore a complex environment, but at a cost of reduced capability. Larger rovers have enhanced capabilities, but at a cost of being somewhat ponderous, especially in complex environments. A hierarchical roving concept attempts to optimize the best of these extremes by carrying a hierarchy of smaller specialized rovers within a larger one. The larger carrier rover acts as a communications relay and power recharge source for the smaller rovers and transports them collectively to a deployment site. After having been deployed and executing their respective missions, the smaller rovers are recovered by the carrier rover and then transported to the next site. Additional benefits of this approach include redundancy, spatially distributed capability, greater situational awareness, and the opportunity for self-rescue. Design and construction experience with a carrier rover containing three smaller specialized rovers is discussed, as are the design tradeoffs.
The selection of rover size, whether the environment be on land, in the sea or air, or on the surface of another world, necessarily entails certain tradeoffs. These tradeoffs include vehicle mass, power source, speed, range, size of obstacles that can be dealt with, sensor compliment, and ultimately, mission objectives. Smaller sized vehicles have advantages in that they tend to be more nimble and can more closely explore a complex environment, but, in general, at a cost of reduced capability in all other areas. Larger vehicles enhance these capabilities, but at a cost of being somewhat ponderous, especially in complex environments. Hierarchical roving seeks to maximize the best of these extremes by carrying a hierarchy of smaller specialized rovers within a larger one. The larger rover acts as a carrier vehicle, communications relay, and power recharge source. The smaller specialized vehicles are deployed at a given site, execute their mission, are then recovered by the carrier vehicle, and finally transported to the next site. Greater situational awareness and the opportunity for self-rescue are additional benefits of hierarchical roving. Experience with a carrier vehicle containing three smaller vehicles is discussed, as are the design tradeoffs.
When we look through ordinary window pane glass, we see the world through a 2-dimensional optical delay line of approximately 27 picoseconds duration. Were the window made of Diamond, this delay would increase to about 42 picoseconds. Suppose it was possible to increase the effective index of refraction by 18 orders of magnitude. This is the basis of Slow Glass. On-going advances in Electromagnetically Induced Transparency, Bose-Einstein Condensates, Self Induced Transparency, and "Frozen" Light provide engineering pathways toward the realization of Slow Glass. These various approaches to group velocity delay will be compared in various media such as cold gas, hot gas, solid state, fiber optics, and drifting medium in terms of complexity, stability, and magnitude of delay. Design examples will be presented and potential applications discussed.
Attempts to detect extraterrestrial life in-situ are complicated by the possibility of local geochemistry posing as biochemistry. A means is presented to discriminate biotic and abiotic signatures by the time resolved response of progressively smaller sample sizes when added to growth media. A purely geochemical response should show a linear reduction in response as the sample size decreases, however, the effects of saturation must be considered. A biochemical response should show a characteristic growth curve whose onset is progressively delayed with smaller sample sizes. Significantly, the overall shape of the growth curve would remain invariant. Potential complications include variations in growth dynamics such as short lifetimes and/or high mortality rates. A third case is also considered where both geochemical and biochemical responses are present. Experimental resulsts are presented using an electrochemical approach.
The term Intelligent Highway is usually intended to mean external systems that are added to pre-existing highways. However, the ability to construct basic passive electronic elements is demonstrated employing electrically dissimilar Portland cement pastes. These electronic elements include resistors, rectifying pn-junctions, piezoelectric and piezoresistive sensors, and thermocouple junctions. It may therefore be possible to build intelligence into the highway
itself utilizing cement-based electronic devices. As compared to semiconductor-based electronic components, those derived from cement have minimal materials and processing costs, do not require clean rooms, and are mechanically more rugged. Results and characterizations are presented for resistive elements and rectifying pn-junctions derived from admixtures of stainless steel fiber (n-type) and carbon fiber (p-type) in Portland cement. These elements are then combined to produce a monolithic cement-based digital logic 2-input AND gate.
Telepresence and teleoperation permit the ability to sense and interact with a remote and potentially hazardous environment without the difficulty of getting there, being there, and then returning safely. Previous telepresence demonstrations have employed only a single remote device or vehicle which, if it experiences difficulty, may require human intervention for rescue, or be abandoned if the rescue is too hazardous. Multiple remote device or vehicle deployment opens the opportunity for interaction to improve the chances for mission success. With a sufficiently large number of remote devices or vehicles, whose interaction is conveyed over high speed internet links, a large body of simultaneous remote users can result. Imposing an access fee structure can result in an enterprise which is economically self-supporting when conducted on a sufficiently large scale. Various levels of interaction, ranging from active participant to active viewer to passive viewer, have corresponding levels of access fee. Experiences in achieving group telepresence among a small fleet teleoperated vehicles are discussed, as are simple solutions to complex issues of inter-vehicle awareness. A general economic model is presented for a large scale "telepresence safari" that is economically self-supporting. The potential for large scale Lunar telepresence is also discussed.
Microbial biofuel cells generate electrical power through the collection of respiratory electrons, which are liberated by the metabolism of nutrients by microorganisms. In the context of in-situ detection of extraterrestrial life, the following question is raised: if microorganisms can be used to generate electrical power, under what circumstances can the generation of electrical power be used to indicate the presence of microbial life? Such an approach to the detection of microorganisms is susceptible to the same ambiguities as similar approaches in that local geochemistry may produce a signal that mimics the presence of life. Consideration is given to time -resolved signal observation to the discrimination of biochemistry and geochemistry and how this approach may be combined with alternate approaches to build a case for, or against, the presence of life. Construction and operation details of microbial biofuel cells, based on marine sediments, are discussed, as are considerations for space flight hardware.
Parametric down conversion permits the generation of entangled photon pairs. However, the production rate is unfortunately very low, typically with nine to ten orders of magnitude between input and output power. A combination of approaches is considered to significantly enhance the overall prodcuiton rate. The use of large crystals simply improves the production rate by increasing the interaction length, as does the use of beam-folding optics. Since the produced entangled photon pairs have twice the wavelength of the pump beam, the use of 'hot' and 'cold' mirrors can be used to redirect unused pump power back into the crystal. Analysis of these approaches is used to indicate a potential improvement of six orders of magnitude. Practical design limitations such as the rejection of waste heat, currently available crystal dimensions, and differential walkoff of correlated photons due to birefringence are considered. Application to type I and type II parametric down conversion and walkoff compensation techniques are detailed. Application to an entangled optical communication link and its use over astronomical distances are outlined.
In-situ observation and exploration of the deep-sea environment presents considerable challenges and hazards. Teleoperation of remotely piloted vehicles (RPV) provides an opportunity for continuous telepresence, however, such missions are energy intensive both for propulsion and illumination. Tethered vehicles are limited in range and the need for a weather-dependent surface support ship. An approach is presented which utilizes a shore-based power line/fiber optic cable connected to a deep-sea recharge site. Free flying RPVs periodically recharge batteries and send video and data back to the surface. The recharge site can be relocated to expand the exploration area, and the entire mission remains underwater for the mission duration. The Hudson submarine canyon provides an ideal test site due to its proximity to a large user population area (New York City) and its geological and biological diversity. Alternate test sites and vehicle design issues are detailed. An access fee structure over the Internet for general public participation is discussed, and the possibility of an economically self-supporting venture when conducted on a sufficiently large scale is also considered.
Teleoperation provides a means for in-situ continuous observation of, and interaction with, remote sites that are difficult and potentially hazardous to access directly. The Hudson submarine canyon, with its proximity to a large population center is an ideal test bed for an on-going teleoperation approach to its exploration and observation. To facilitate a long duration mission and freedom from an expensive and weather dependent surface support ship, an underwater electrical recharge site is proposed. A power line/fiber optic cable is placed from shoreline facilities to the recharge site, located on the upper rim of the canyon at approximately 100 meter depth. Here, free flying remotely piloted vehicles periodically recharge batteries and send video/data back to the surface. The entire venture is located underwater and remains there for the duration of the mission. The recharge site can be relocated to expand the exploration area. Various alternate canyon sites worldwide are considered. Internet access, and an access fee structure for the general public, presents the possibility of an economically self-supporting venture when conducted on a sufficiently large scale.
Recent advances in bright sources of entangled photons are combined with demonstrations of Electromagnetically Induced Transparency (EIT) to suggest a design model for an optical data link whose propagation delay is distance invariant. Intense entangled photon streams P and P' are directed into a transmitting telescope and an optical delay line respectively. The optical delay line is constructed of an extended region of EIT to reduce the local velocity of light many orders of magnitude, while experiencing no loss. A design example employing Rubidium vapor is presented. The delay line is adjusted so that as the entangled photon stream P is about to arrive at the receiver, the first photon of stream P' emerges from the delay line. A second entanglement operation on P' imposes a polarization on this photon which simultaneously appears as the compliment on the remote entangled photon of stream P. The process continues on remaining photons of both streams. An optical link budget approach is used to calculate required intensities, conversion efficiencies, apertures and received irradiances. Polarization modulation sequences are used in a transponder mode to measure the varying distance between transmitter and receiver iteratively and is used to adjust and track the optical delay line. Application to astronomical distances is considered.
The mass appeal of space exploration on an interactive, personal level, is readily demonstrated by the popular success of the Mars Pathfinder mission, and the availability of "live" pictures over the internet. Over a half billion accesses to the NASA sites were recorded during the first 30 days on Mars, with a peak of over 46 million accesses on July 8, 1997 alone. The proximity of the Lunar surface provides near realtime opportunities for telepresence relying only on previously demonstrated technologies. A stereoscopic-vision Virtual Reality approach provides the sense of "being there" without the difficulties of getting there, and back. Internet access provides Earth-bound users with a hierarchy of potential levels of interaction, from vehicle driver, to active viewer, to passive viewer, from the Moon. An access fee structure can make such a venture economically self supporting when conducted on a sufficiently large scale [1 ] . A base- line study is presented consisting of a small fleet of 10 vehicles, each with a compliment of 50 remote-directed stereoscopic camera heads. Technical issues such as the problems encountered in an on-going operation on the Lunar surface are discussed. Consequences of temperature extremes, high vacuum, solar radiation, micrometeorites, abrasive nature of Lunar dust and its wide particle size distribution and the ability to electrostatically attach to surfaces are considered as they affect vehicle design and operation. An optical data link is described.
12 A large scale Lunar teleoperation project has been proposed consisting of a small fleet of ten Lunar roving vehicles, each with a compliment of fifty remotely steerable stereoscopic camera heads. Earth-bound users gain access through the Internet with a hierarchy of participation, ranging from vehicle driver, to active viewer, to passive viewer. Earth uplink to the Moon consist of vehicle piloting and camera head positioning commands, and are of relatively low bandwidth. The Moon-to-Earth downlink, however, must have sufficient bandwidth to handle 500 simultaneous stereoscopic video feeds. An optical communication link is described, first as a free space link between the Moon and Low Earth Orbiting satellites, and second, with atmospheric effects for ground-based reception. Link budget and aperture/power tradeoffs for various baseline designs are considered. Technical challenges of operating in a Lunar environment are described.
Thin films of Buckminsterfullerene exhibit a reversible electrochromic effect when electrochemically intercalated with alkali metal or alkali earth ions. The degree of reversibility depends on the ratio of intercalated ions to fullerene molecules, both in the bulk film thickness and in localized stoichiometric gradients. High ratios of ions to fullerenes product films with limited electrochromic reversibility. These films are also soluble in the polar organic electrolyte system, leading to cycling and durability issues. If the intercalating ion current is modulated, rather than continuously applied, improved durability and reversibility result. The relationship of stoichiometric gradients to intercalation ion current density and ion mobility in the fullerene film are considered, as are optimum pulse-widths. Film preparation and electrolyte preconditioning are detailed.
The electrochromic effect is observed in fullerene thin films when, under applied electric field, various ionic species are intercalated into the interstitial spaces between fullerene molecules. Within limits, the process is electrically reversible. Residual oxygen, both in the electrolyte system and in the fullerene thin film itself, as well as trace water levels, significantly degrade electrochromic stability. The degree of electrochromic intercalation affects reversibility. However, this is complicated by the mobility of the intercalant ion and the resulting stoichiometric gradients within the fullerene thin film. The details of film preparation and electrolyte preconditioning are discussed, in addition to time-resolved transparency changes during forward and reverse electrochemical intercalation. Potential applications in large area non-volatile flat panel displays and integrated optoelectronic devices are also considered.