Dark Markings Research Articles

Intergradation of Osage and Broad-Banded Copperheads in Kansas

The broad-banded copperhead (Agkistrodon contortrix laticinctus) was named by Gloyd and Conant (1934) as a western subspecies in Texas and Oklahoma distinct from two eastern subspecies then recognized. The Osage copperhead (A. c. phaeogaster) was named later (Gloyd, 1969) from northeastern Kansas and Missouri. Areas of intergradation between laticinctus and phaeogaster have been reported in Oklahoma and Kansas (Webb, 1970; Smith, 1950, 1956; Collins, 1974, 1982) and certain specimens from Chautauqua and Cowley counties in southern Kansas have been referred to as intergrades (Gloyd and Conant, 1943; Caldwell and Collins, 1977; Capron, 1978). Capron (1978) described his experiences with copperheads on field trips to the Walnut River and adjacent bluffs in southern Cowley County. Two of 13 copperheads captured were considered broad-banded, ten were most like Osage copperheads, and one specimen was somewhat intermediate. Striking variation in both pattern and color was noted, but none of the 13 copperheads was preserved. Caldwell and Collins (1977), using two specimens (KU 159834-835) from Chautauqua County and three (KU 159980, 170634-635) from Cowley County, felt that slight intergradation between laticinctus and phaeogaster took place in southern Kansas. On 12 May 1983 seven copperheads (KU 193228-234) were collected by Fitch at Buck Creek, 2.5 km WSW Hewins, Chautauqua County, Kansas. These supplement five uncataloged specimens from Cowley County in the Southwestern College collection of Winfield, eight other specimens (KU 37721-723, 159980, 170634-635, 174558, 187791) from Cowley County, and two (KU 159834835) from Chautauqua County. These 22 copperheads permit a better evaluation of intergradation between laticinctus and phaeogaster in Kansas. A. c. laticinctus is characterized by having body bands widened, covering 7-14 scale rows on the sides and 5-8 rows middorsally .... not much narrower middorsally than on the sides (more than half as wide at midline as on the lowest lateral row), extending across the lateral ends of the ventral scutes and more or less continuous with the dark markings of the belly

Radio Science with Voyager 2 at Saturn: Atmosphere and Ionosphere and the Masses of Mimas, Tethys, and Iapetus

Voyager 2 radio occultation measurements of Saturn's atmosphere probed to the 1.2-bar pressure level, where the temperature was 143 +/- 6 K and the lapse rate apparently equaled the dry adiabatic value of 0.85 K per kilometer. The tropopause at both mid-latitude occultation locations (36.5 degrees N and 31 degrees S) was at a pressure level of about 70 millibars and a temperature of approximately 82 K. The stratospheric structures were very similar with the temperature rising to about 140 K at the 1-millibar pressure level. The peak electron concentrations sensed were 1.7 x 10(4) and 0.64 x 10(4) per cubic centimeter in the predawn (31 degrees S) and late afternoon (36.5 degrees N) locations. The topside plasma scale heights were about 1000 kilometers for the late afternoon profile, and 260 kilometers for the lower portions and 1100 kilometers for the upper portions of the topside predawn ionosphere. Radio measurements of the masses of Tethys and Iapetus yield (7.55 +/- 0.90) x 10(20) and (18.8 +/- 1.2) x 10(20) kilograms respectively; the Tethys-Mimas resonance theory then provides a derived mass for Afimas of (0.455 +/- 0.054) x 10(20) kilograms. These values for Tethys and Mimas represent major increases from previously accepted ground-based values, and appear to reverse a suggested trend of increasing satellite density with orbital radius in the Saturnian system. Current results suggest the opposite trend, in which the intermediate-sized satellites of Saturn may represent several classes of objects that differ with respect to the relative amounts of water, ammonia, and methane ices incorporated at different temperatures during formation. The anomalously low density of lapetus might then be explained as resulting from a large hydrocarbon content, and its unusually dark surface markings as another manifestation of this same material.

AGU awards the Twentieth Presentation of the James B. Macelwane Award to Ronald J. Prinn, David Southwood, and Donald J. Weidner

Mr. President, ladies, and gentlemen: We are honoring tonight a young scientist who combines an unusually broad knowledge of the chemistry and dynamics of planetary atmospheres with a healthy skepticism regarding established dogma and a marvelous ability to shrug off the displeasure of established dogmatists.Ron Prinn's theoretical research has significantly influenced our understanding of the terrestrial stratosphere as well as the atmospheres of Venus and Jupiter. Since 1980, when he joined the Department of Meteorology at Massachusetts Institute of Technology, he has been a leading participant in collaborative efforts to develop numerical models of the stratosphere combining comprehensive chemistry with realistic dynamics. Such models have been a rich source of controversy in our continuing efforts to predict man's potential impact on the ozone layer. Prinn's work on the chemistry of sulfur gases in the atmosphere of Venus, published in 1973 and 1975, foreshadowed the explosive growth of interest in the sulfur chemistry of the terrestrial atmosphere. By delimiting conditions for the predominance of either sulfur or sulfuric acid in the clouds of Venus, his work provided a basis for the interpretation of Pioneer Venus data. It was Prinn who suggested that the spectacular dark markings on ultraviolet images of Venus are caused by sulfur. More recently he has discussed the contribution of phosphorus to the color of the Great Red Spot on Jupiter. Not forsaking the mother planet, he is currently engaged in efforts to determine from field measurements whether there is any truth in the well‐established theory that freon, methyl chloroform, and nitrous oxide are chemically inert in the troposphere.

Temporal changes in the Cerberus region of Mars: Mariner 9 and Viking comparisons

Mariner 9 images of the Cerberus dark region of Mars obtained in 1972 are compared with Viking Orbiter 1 images obtained in 1978 to investigate temporal changes in the appearance of the region. Changes in the outline of the albedo feature in the six years between observations are found which resulted in an increase in total area by about 1.2%, with a shift in the boundary of the southwestern region by as much as 90 km. Darkening of many areas of Cerberus is also observed, resulting in the development of a more uniform dark tone and accompanied by the disappearance of dark filamentary markings observed in 1972. Although neither streaks associated with craters and knobs are found to vary in mean length, a change in the mean orientation of bright streaks is observed. These changes are explained by eolian redistribution and the removal of bright material during major dust storms.

TONGUE-SHAPED CRACK EXTENSION DURING FATIGUE OF HIGH STRENGTH ALUMINIUM ALLOYS

Abstract— Fracture surfaces of both service and laboratory fatigue fractures frequently show dark tongue-shaped marks. In fatigue tests on 7075–T6 specimens such tongues were produced by high peak loads. Measurements indicated that a tongue is not formed during a single burst of crack extension but is the result of a number of successive pop-ins requiring an increasing load. Therefore tongue formation is a quasi-stable phenomenon. The tunnelling fracture in the centre of plate thickness is accompanied by unfailed ligaments at the plate surfaces which reduce the stress intensity at the crack tip. The effect of different material conditions and loading direction on tongue forming was studied. A new model was developed to describe the growth of a tongue. The model was in good agreement with the various test results. The analysis of the problem has some relevance to validity requirements for K1c. A formula pertaining to tongues proposed by Forsyth was slightly modified and found to be approximately correct for the present results.

An almost fatal case of marine stinger (sea wasp, box jelly-fish or chironex fleckeri)

A brief review of previous literature indicates that Townsville region has the largest number of reported deaths in the world due to box jelly-fish which abound in Australasian oceans. A 20-yr-old white pregnant female was sitting in Rowes Bay, Townsville, (shallow water), on 19 March 1979. Suddenly she screamed with pain and became irrational. According to bystanders respiratory arrest occurred and pulse was absent. A nurse who was on the beach gave her mouth-to-mouth artificial resuscitation. The owner of the caravan park, nearby, doused her with ‘metho” and “stingose’, literally within minutes. She was rushed to Townsville General Hospital in an ambulance. On examination at 12.30 pm she was unconscious, very restless and agitated, with wheezy respirations. She was treated by intubation, O2, I.V. morphine, antivenene. Extensive dark pink-red weal marks appeared on left thigh, hand, forearm and lower abdomen with oedema and blistering, total WBC count was 32,700 with 9% basophils, 1% metamyelocytes and toxic granulations. Nematocysts were obtained from the skin lesions and the diagnosis was established. She delivered a normal baby in May 1979. A brief review of previous literature indicates that Townsville region has the largest number of reported deaths in the world due to box jelly-fish which abound in Australasian oceans. A 20-yr-old white pregnant female was sitting in Rowes Bay, Townsville, (shallow water), on 19 March 1979. Suddenly she screamed with pain and became irrational. According to bystanders respiratory arrest occurred and pulse was absent. A nurse who was on the beach gave her mouth-to-mouth artificial resuscitation. The owner of the caravan park, nearby, doused her with ‘metho” and “stingose’, literally within minutes. She was rushed to Townsville General Hospital in an ambulance. On examination at 12.30 pm she was unconscious, very restless and agitated, with wheezy respirations. She was treated by intubation, O2, I.V. morphine, antivenene. Extensive dark pink-red weal marks appeared on left thigh, hand, forearm and lower abdomen with oedema and blistering, total WBC count was 32,700 with 9% basophils, 1% metamyelocytes and toxic granulations. Nematocysts were obtained from the skin lesions and the diagnosis was established. She delivered a normal baby in May 1979.

Seasonality in habitat selection by the gold color morph of Cichlasoma citrinellum and its relevance to sympatric speciation in the family Cichlidae

Cichlasoma citrinellum is a polymorphic species whose individual coloration varies from the dark grey markings typical of the species to yellow, orange, and red. In Lake Jiloa, Nicaragua the depth distribution of these latter, nongrey, golden morphs shows dramatic seasonal variation. In the height of the dry season in February over 50% of the gold morphs occur above 9 m, but as the breeding season approaches they migrate deeper such that less than 7% of the gold population occurs above 9 m at the onset of the breeding season. During the rainy season when breeding occurs most of the gold morphs occur below 15 m. It appears that gold morphs ‘voluntarily’ move into deeper water to breed rather than being aggressively forced deeper by larger, territorial grey morphs as was implied in an earlier paper (McKaye & Barlow 1976). Since the morphs of this species assortatively mate and select different habitats in which to breed, future sympatric splitting of this species is possible. Likely examples of sympatric speciation and of incipient speciation in the family Cichlidae are discussed.

Wavelength dependence of polarization. XXXIV - Observations of Venus

Polarimetric observations of linear polarization on Venus are presented. The observations, which cover nine small disk areas as well as the whole disk, were made with seven filters between 0.3 and 1 micron and also with three filters in the range from 1.2 to 2.2 microns. A polarization wavelength dependence is determined which appears to confirm Landau's (1975) discovery of a steep rise in polarization near 3 microns. The dark UV markings on Venus are shown to be regions of more positive UV polarization and are interpreted as a general feature of a gaseous atmosphere in which sulfuric acid droplets are suspended.

Correlation of simultaneous ultraviolet (0.36 μm) and infrared (8 to 14 μm) images of Venus

We present evidence for a correlation between features observed in simultaneous infrared (8 to 14 μm) and ultraviolet (0.36 μm) images obtained during Venus' 1975 and 1977 apparitions. The sense of the observed correlation is such that bright uv markings correspond to bright (warm) ir features, and similarly, dark uv markings correspond to dark (cool) ir features.

Phobos: Photometry and origin of dark markings on crater floors

Viking Orbiter 1 close encounter pictures of Phobos reveal unusual dark patches on the floors of many craters. Photometry of these features indicates that they have a similar normal reflectance but a phase coefficient 30% larger than the average surface. These facts suggest that the "dark" material has a similar composition but a much rougher texture than the average surface of Phobos. By analogy with terrestrial impact, explosion and laboratory craters, the dark patches are interpreted as impact generated melt pools which remain visible on Phobos due to the low value of g and consequent small amount of fallback ejecta and slumping. Since blanketing by ejecta from subsequent impacts and micrometeoroid erosion should eventually obliterate such features, they should be more conspicuous in the fresher craters. Similar features should be visible on small asteroids and other low g bodies. However, they are not prominent on the surface of Deimos—possibly because most of the craters imaged at high resolution on the outer satellite appear to have been blanketed by several meters of fine‐grained material.

Color of Kerogen as Index of Organic Maturity

Kerogen from the Tanner basin off southern California was heated under nitrogen at different temperatures and times and subsequently was studied under the transmitted light microscope. Samples darken in color from yellow through shades of brown to black with increasing thermal maturation. The transition from dark brown to very dark brown marks the range of maximum n-alkane generation where the residue attains an atomic H/C of about 0.80 plus or minus 0.05. The apparent activation energy for this transition was about 45 plus or minus 5 kcal per mole.

Photometry of Venus from Mariner 10

Photometry of the upper atmosphere of Venus from Mariner 10 on February 5, 1974 is discussed with respect to in-flight verification of camera linearity, shading, and absolute photometric calibration. Among photometric results are the following: (1) temporal brightness variations were observed in the UV greater than 10% over a few hours due to the rapid rotation of the upper atmosphere, (2) the observed terminator was 4 degrees past the geometric terminator due to detached haze layers at altitudes around 85 km, (3) there were no indications of cloud top elevation variations greater than a few hunderd meters, and (4) in the UV, the bright and dark regions both had low albedos in all scales, showing that the UV absorber is not confined just to dark markings.

Variable features on Mars. VII. Dark filamentary markings on Mars

Some Mariner 9 B-frames show networks of criss-crossing rectilinear albedo markings typically 10 km long by 100 m wide. This paper discusses the location, variability and possible nature of these dark filamentary markings. Although not common on Mars, the markings are concentrated in at least two areas: Depressio Hellespontica and Cerberus/Trivium Charontis. In Depressio Hellespontica their emergence coincided with a general darkening of the region which occurred 2 months after the end of the 1971 global duststorm. The very definite criss-cross pattern of many of these markings suggests that they may be controlled by joints. It is unlikely that the markings are linear dunes.

Albedo boundaries on Mars in 1972: Results from Mariner 9

A map of “albedo” boundaries (light and dark markings) on Mars was prepared from Mariner 9 images. After special digital processing, these pictures provide detailed locations of albedo boundaries, which is significant in interpreting recent eolian activity. Derivation of absolute albedo values from the spacecraft data was not attempted. The map correlates well with telescopic observations of Mars after the 1971 dust storm.

The Composition of the Ultraviolet Dark Markings on Venus

The ultraviolet dark clouds are an ephemeral phenomenon in the Venus atmosphere, apparently just near the limit of stability. The UV dark material is moderately abundant, perhaps 10%, since the contrasts between light and dark material are some 20%. The material should absorb light between 3000–4000 Å, and ideally should also have visible absorptions in the blue, as the overall spectral albedo of Venus indicates. Such a material is bromine dissolved in hydrobromic acid. Solar radiation near 2500 Å is sufficient to partially photolyze HBr into Br2. HBr in the Venus atmosphere is inferred to have a mixing ratio of 10−4 versus CO2. With a water vapor mixing ratio of 10−3, droplets of hydrobromic acid are possible. These droplets would eventually evaporate in the drier upper atmosphere. The refractive index of these hydrobromic acid droplets of 52% (by weight) composition is 1.46, within the limits set by polarization studies of Venus.

Spectroscopic Observations of Winds on Venus

Measurements of the differential Doppler shift between various points on Venus using a high-resolution PEPSIOS interferometer. Using both a CO2 line and a Fraunhofer line a mean zonal-wind velocity of about -83 m/s is found near the equator; the velocity appears to vary from about -2 to -125 m/s with a time scale of greater than one week. Meridional velocities are measured to be weak. The equatorial zonal velocity appears to be smaller in the 'morning' than in the 'afternoon'. A comparison with reported velocities of the ultraviolet dark markings reveals general agreement in that both find the motion to be retrograde, variable, and accelerated during the day. A new potential source of systematic error in all spectroscopic determinations of the differential Doppler shift of nonuniformly illuminated objects is pointed out.

Static electricity causing treelike dark markings

Static electricity causing treelike dark markings

Preliminary Infrared Radiometry of Venus from Mariner 10

The intensity of emission at 45 micrometers, measured with high spatial resolution along a single crossing of the Venus disk, is presented. On the average, the observed darkening toward the limb varies nearly linearly with the cosine of the emission angle. The brightness temperature, extrapolated to normal emission, is 255 degrees K. The limb darkening curve, interpreted in a linear approximation, implies that the atmosphere is quite opaque, with an absorption coefficient of 0.24 per kilometer. Changes in curvature present in the limb darkening curve suggest the existence of thermal inhomogeneities with scale comparable to that of the dark markings shown by ultraviolet images.

Variable features on Mars, 2, Mariner 9 global results

Systematic Mariner 9 monitoring of the space and time distribution of Martian bright and dark markings, the streaks and splotches, indicates a range of global correlations. The time variable classical dark markings owe their configurations and variability to their constituent streaks and splotches, produced by windblown dust. Streaks and splotches are consistent wind direction indicators. Correlation of global streak patterns with general circulation models shows that velocities ∼50 to 90 m/sec above the boundary layer are necessary to initiate grain motion on the surface and to produce streaks and splotches. Detailed examples of changes in Syrtis Major, Lunae Palus, and Promethei Sinus are generally consistent with removal of bright sand and dust and uncovering of darker underlying material as the active agent in such changes, although dark mobile material probably also exists on Mars. The generation of streaks and the progressive albedo changes observed require only threshold velocities of about 2 m/sec for about 1 day at the grain surface. We propose that the dark collar observed following the north polar cap in its retreat is produced by the scouring of bright overlying dust from the polar peripheral ground by winds driven by the temperature differences between frosted and unfrosted terrain. The stability of bright streaks and the variability of dark streaks and splotches, as well as their contrast, can be the result of size differences of the constituent particles.

Some comments on the low intensity H? emission observed by J.-L. Leroy in the solar corona

Some comments are presented on the important observations of faint prominences made recently by Dr Jean-Louis Leroy at the Pic du Midi Observatory. The writer draws attention to the very probable connection with faintly luminous Hα obscuring prominences which appear sometimes as dark lanes and markings in ordinary prominences.