The variability of stratospheric nitrogen compounds observed by LIMS in the winter of 1978–1979

The LIMS experiment was launched on the Nimbus 7 satellite for the purpose of sounding the vertical structure of temperature and key upper atmosphere trace gases on a global scale. The technique of thermal infrared limb sounding was used to obtain measurements of O₃, H₂O, NO₂, and HNO₃. LIMS collected data almost continuously from late October to late May over the latitude range from 64°S to 84°N. Two of the gases, NO₂ and HNO₃, are important elements in the NO_x chain of chemical reactions leading to ozone destruction. We will describe results for these gases in terms of zonal mean profiles and latitudinal distributions. The period selected for study is January–May 1979, when a major stratospheric warming occurred.     

Leaky Coaxial Cable Resource Protection Sensor Performance Analysis

The performance of an RF intrusion detection system which uses a leaky coaxial cable sensor is analyzed. A simple cable sensor field model is assumed which gives good agreement between the computed response and observation. Expressions that describe the performance of several deployment configurations and receiver types are developed. The probability of detection and the zone of containment are computed and their uniformity is examined as a function of cable propagation constants.     

Calculating Detection Probabilities for Systems Employing Noncoherent Integration

Cumulative probability distributions that occur in radar and sonar detection problems are calculated directly from the characteristic function by using a Fourier series. The error in the result is controlled by two parameters which can be adjusted to suit the application. The technique is applied to the problem of determining the detection performance of consecutive discrete Fourier transforms (DFTs) for a narrowband Gaussian signal with a rectangular spectrum. Since the characteristic function is used directly in its product form this technique does not suffer from the numerical problems associated with the partial fraction approach. The technique can handle many different problems in a single computational structure making it a valuable tool in system performance studies.     

The Effect of Pulse Shape and Duty Cycle on Laser Binary Communication Systems

The result of an investigation of the effects of pulse shape and duty cycle on the probability of error are presented for a pulse-gated binary modulation (PGBM) laser communication system when the background irradiance has the important Lorentzian spectral shape.     

Near-infrared detection of potential evidence for microscopic organisms on Europa

The possibility of an ocean within the icy shell of Jupiter's moon Europa has established that world as a primary candidate in the search for extraterrestrial life within our Solar System. This paper evaluates the potential to detect evidence for microbial life by comparing laboratory studies of terrestrial microorganisms with measurements from the Galileo Near Infrared Imaging Spectrometer (NIMS). If the interior of Europa at one time harbored life, some evidence may remain in the surface materials. Examination of laboratory spectra of terrestrial extremophiles measured at cryogenic temperatures reveals distorted, asymmetric nearinfrared absorption features due to water of hydration. The band centers, widths, and shapes of these features closely match those observed in the Europa spectra. These features are strongest in reddish-brown, disrupted terrains such as linea and chaos regions. Narrow spectral features due to amide bonds in the microbe proteins provide a means of constraining the abundances of such materials using the NIMS data. The NIMS data of disrupted terrains exhibit distorted, asymmetric near-infrared absorption features consistent with the presence of water ice, sulfuric acid octahydrate, hydrated salts, and possibly as much as 0.2 mg cm(-3) of carbonaceous material that could be of biological origin. However, inherent noise in the observations and limitations of spectral sampling must be taken into account when discussing these findings.     

Finding extraterrestrial organisms living on thermosynthesis

During thermal cycling, organisms could live on thermosynthesis, a theoretical mechanism applicable to the origin of life and the early evolution of biological energy conversion. All extraterrestrial ice may be a repository for frozen dead or dormant organisms from earlier stages of evolution. In the presence of a thermal gradient within the ice, organisms might still be harvesting energy from thermosynthesis. Possible habitats for thermosynthesizers can be found throughout the Solar System, particularly in the cold traps on Mercury and the Moon, convecting waters on Mars, the oceans on moons in the outer Solar System, and smaller bodies rotating in the sunlight such as cosmic dust, meteorites, asteroids, and comets. A general strategy for detecting thermosynthetic organisms on Earth is offered, and highlights of current and upcoming robotic exploratory missions relevant to the detection of thermosynthesis are reviewed.     

Induced abnormality in Mir- and Earth grown Super Dwarf wheat.

Super-dwarf wheat grown on the Mir space station using the Svet "Greenhouse" exhibited morphological, metabolic and reproductive abnormalities compared with Earth-grown wheat. Of prominent importance were the abnormalities associated with reproductive ontogeny and the total absence of seed formation on Mir. Changes in the apical meristem associated with transition from the vegetative phase to floral initiation and development of the reproductive spike were all typical of 'Super-Dwarf' wheat up to the point of anthesis. Observation of ruptured anthers from the Mir-grown plants revealed what appeared to be normally developed pollen. These pollen gains, however, contained only one nuclei, while normal viable pollen is tri-nucleate. A potentially important difference in the flight experiment, compared with ground reference studies, was the presence of a high level of atmospheric ethylene (1,200 ppb). Ground studies conducted by exposing 'Super-Dwarf' wheat to ethylene just prior to anthesis resulted in manifestation of the same abnormalities observed in the space flight samples.     

Life before RNA

The hypothesis that life originated and evolved from linear informational molecules capable of facilitating their own catalytic replication is deeply entrenched. However, widespread acceptance of this paradigm seems oblivious to a lack of direct experimental support. Here, we outline the fundamental objections to the de novo appearance of linear, self-replicating polymers and examine an alternative hypothesis of template-directed coding of peptide catalysts by adsorbed purine bases. The bases (which encode biological information in modern nucleic acids) spontaneously self-organize into two-dimensional molecular solids adsorbed to the uncharged surfaces of crystalline minerals; their molecular arrangement is specified by hydrogen bonding rules between adjacent molecules and can possess the aperiodic complexity to encode putative protobiological information. The persistence of such information through self-reproduction, together with the capacity of adsorbed bases to exhibit enantiomorphism and effect amino acid discrimination, would seem to provide the necessary machinery for a primitive genetic coding mechanism.