Enstatite: disorder produced by a megabar shock event

Shocked Bamle enstatite partly transforms to disordered enstatite. Debye-Scherrer patterns of some shocked material are almost identical to those of disordered enstatite from portions of various enstatite achondrites. No disorcdered single crystals have been found.     

The surface of Mars: there view from the viking 1 lander

The first photographs ever returned from the surface of Mars were obtained by two facsimile cameras aboard the Viking 1 lander, including black-and-white and color, 0.12 degrees and 0.04 degrees resolution, and monoscopic and stereoscopic images. The surface, on the western slopes of Chtyse Planitia, is a boulder-strewn deeply reddish desert, with distant eminences-some of which may be the rims of impact craters-surmounted by a pink sky. Both impact and aeolian processes are evident. After dissipation of a small dust cloud stirred by the landing maneuvers, no subsequent signs of movement were detected on the landscape, and nothing has been observed that is indicative of macroscopic biology at this time and place.     

The composition of phobos: evidence for carbonaceous chondrite surface from spectral analysis

A reflectance spectrum of Phobos (from 200 to 1100 nanometers) has been compiled from the Mariner 9 ultraviolet spectrometer, Viking lander imaging, and ground-based photometric data. The reflectance of the martian satellite is approximately constant at 5 percent from 1100 to 400 nanometers but drops sharply below 400 nanometers, reaching a value of 1 percent at 200 nanometers. The spectral albedo of Phobos bears a striking resemblance to that of asteroids (1) Ceres and (2) Pallas. Comparison of the reflectance spectra of asteroids with those of meteorites has shown that the spectral signature of Ceres is indicative of a carbonaceous chondritic composition. A physical explanation of how the compositional information is imposed on the reflectance spectrum is given. On the basis of a good match between the reflectance spectra of Phobos and Ceres and the extensive research that has been done to infer the composition of Ceres, it seems reasonable to believe that the surface composition of Phobos is similar to that of carbonaceous chondrites. This suggestion is consistent with the recently determined low density of Mars's inner satellite. Our result and recent Viking noble gas measurements suggest different modes of origin for Mars and Phobos.     

Communications Satellites: Countdown for INTELSAT VI

Since the formation of COMSAT 20 years ago, the number of international telephone circuits made through satellites has grown 400 times and the cost of a telephone call has decreased by 12,000 percent. Worldwide communications linking 109 nations are achieved with 14 satellites in earth-synchronous orbit. Advances in microwave technology have expanded the transmission bandwidth per satellite from 50 to more than 3000 megahertz. Improvements in solar cell, battery, stationkeeping, and microwave amplification technology have increased satellite lifetime from 1.5 years to 10. The sixth generation of INTELSAT satellites, now being manufactured, will be introduced into the system in 1986, and each satellite will carry more than 40,000 telephone channels plus two television programs. The next generation of satellites, now under design for expanded capacity, will be needed by the middle 1990's to meet the traffic demand. These satellites are likely to add new frequencies (20 and 30 gigahertz), onboard signal processing and switching, and more bandwidth-efficient modulation, to achieve larger communication capacity at each orbital location.     

Implications of the gas compositional measurements of pioneer venus for the origin of planetary atmospheres

Comparisons are made between the volatile inventories of the terrestrial planets, including Pioneer Venus data, and the predictions of three classes of theories for the origin of planetary atmospheres. Serious difficulties arise for the primary atmosphere and external source hypotheses. The grain accretion hypothesis can account for the trends in the volatile inventory from Venus to Earth to Mars, if volatiles were incorporated into planet-forming grains at nearly the same temperature for all of these planets, but at systematically lower pressures in the regions of planet formation farther from the center of the solar nebula.     

Why gases dissolve in liquids

The thermodynamics and statistical mechanics of solubility are fairly well understood. It is still very difficult, however, to make quantitative predictions of solubility for real systems from first principles. The purposes of this article are to present the results of solubility experiments in some prototype solute-solvent systems, to show how far they may be understood from molecular first principles, and to discuss some of the things that are still missing. The main systems used as examples have the inert gas xenon as solute and some simple organic liquids as solvents.     

Selective chemical catalysis by an antibody

The immunoglobulin MOPC167, which binds the transition state analog p-nitrophenylphosphorylcholine with high affinity, catalyzed the hydrolysis of the corresponding carbonate 1. MOPC167 catalysis displayed saturation kinetics with catalytic constant (kcat) = 0.4 min-1 and Michaelis constant (Km) = 208 microM, showed substrate specificity, and was inhibited by p-nitrophenylphosphorylcholine. The rate of the reaction was first order in hydroxide ion concentration between pH 6.0 and 8.0. The lower limit for the rate of acceleration of hydrolysis by the antibody above the uncatalyzed reaction was 770. This study begins to define the rules for the generation of catalytic antibodies.