Search for organic molecules in the outer solar system

Recent developments of millimeter astronomy have led to the discovery of more and more complex molecules in the interstellar medium. In a similar way, attempts have been made to detect complex molecules in the atmospheres of the most primitive bodies of the Solar System, i.e. outer planets and comets, as well as in Titan's atmosphere. An important progress has been achieved thanks to the continuous development of infrared astronomy, from the ground and from space vehicles. In particular, an important contribution has come from the IRIS-Voyager infrared spectrometer with the detection of prebiotic molecules on Titan, and some complex organic molecules on Jupiter and Saturn. Another important result has been the observation of carbonaceous material in the immediate surroundings of Comet Halley's nucleus. In the near future, the search for organic molecules in the outer Solar System should benefit from the developments of large millimeter antennae, and in the next decade, from the operation of infrared Earth-orbiting spacecrafts (ISO, SIRTF).     

Exobiology and future Mars missions: The search for Mars'' earliest biosphere

The primordial Mars may have possessed a thick carbon dioxide atmosphere, with liquid water common on the surface, similar in many ways to the primordial Earth. During this epoch, billions of years ago, the surface of Mars could have been conducive to the origin of life. It is possible that life evolved on Mars to be later eliminated as the atmospheric pressure dropped. Analysis of the surface of Mars for the traces of this early martian biota could provide many insights into the phenomenon of life and its coupling to planetary evolution.     

LET variation measurements behind different absorber thicknesses on COSMOS-1129 satellite

LET variation with the absorber thickness was measured by plastic detectors exposed on COSMOS-1129 satellite.     

Changes of deoxyribonucleoprotein in the spleen, thymus and liver of rats exposed to weightlessness and artificial gravity aboard the Cosmos biosatellites

Changes of deoxyribonucleoprotein in the spleen, thymus and liver of rats exposed to wegithlessness or artifical gravity on board biosatellites Cosmos 782 and Cosmos 936 after 20 days of flight were investigated. The level of polydeoxyribonucleotides in the spleen and thymus of rats exposed during the flight to weightlessness increased 4 – 11 hours after landing, suggesting breakdown of a part of the deoxyribonucleoprotein present. The use of artifical gravity prevented this breakdown in the thymus but not in the spleen. The breakdown was accompanied in the majority of cases by a decrease in teh deoxyribonucleoprotein content. We believe the breakdown of deoxyribonucleoprotein is due to a nonspecific stress reaction to the change from the weightless state to that of terrestrial gravity during landing. The polydeoxyribonucleotide level and amount of deoxyribonucleoprotein in the majority of cases returned to normal values during the 25 days of readaptation. No substantial change of deoxyribonucleoprotein was found in the liver. The different findings in the three organs are due to the fact that breakdown of deoxyribonucleoprotein takes place in sensitive cells underlying pycnosis. These cells are found in the spleen and thymus, but not in the liver.     

Survival of microorganisms in space: A review

Spores of $\text{Bacillus subtilis}$ were exposed to selected factors of space (vacuum, solar UV radiation, heavy ions of cosmic radiation), and their response was studied after recovery. These investigations were supplemented by ground-based studies under simulated space conditions. The vacuum of space did not inactivate the spores. However, vacuum-induced structural changes in the DNA, and probably in the proteins, caused a supersensitivity to solar UV radiation. This phenomenon is caused by the production of specific photoproducts in DNA and protein, which cannot be removed by normal cellular repair processes. In vegetative bacterial cells, exposed to vacuum, cell dehydration led to damage of the cell membrane, which could be partly repaired during subsequent incubation. The high local effectiveness of the cosmic heavy ions further decreases the chance that spores can survive for any length of time in space. Nonetheless, a spore travelling through space and protected from ultraviolet radiation could possibly survive an interplanetary journey. Such a situation favors panspermia as a possible explanation for the origin of life.     

Spherical accretion of massive black holes: A model for galactic nuclei

The possibility of explaining the continuous emission of active galactic nuclei in the frame of a model of spherical accretion onto a massive black hole is discussed. Cool inhomogeneities (T 10⁴°K) within the accretion flow could be responsible for the broad line emission if half of the accreting matter is in the dense phase. A crucial test of this hypothesis is the expected correlation between the ratio of the luminosity in lines to the total luminosity and the hardness of the continuous spectrum.     

Low energy observations of Cygnus X-2 by Ariel VI

Ariel VI observations of Cygnus X-2 have revealed a rather flat spectrum between 0.1 and 1.5 keV with variable emission at low energy. Of the two conflicting interpretations of this object in terms of i) a distant high-luminosity (L_x 10³⁸ ergs s⁻¹) binary and ii) a nearby low-luminosity (L_x 10³⁵ ergs s⁻¹) degenerate dwarf system, our measurements support the latter.     

X-ray and gamma-ray observations of a white-light flare

HEAO-1 observed hard radiations (X- and gamma-rays) from a major solar flare on 11 July 1978. The observations showed gamma-ray line and continuum emission extending to the highest energy observed. The lines are identified with the 2.2 MeV line of deuterium formation and the 4.4 MeV line of inelastic scattering on ¹²C, both previously observed in the flares of August 1972 [1]. The 11 July flare was identified as a white-light flare by observations at Debrecen [2]. It thus provides the first opportunity for a detailed examination of white-light flare theories that depend upon proton heating of the photosphere. The line strength over a four-minute integration at 2.2 MeV was 1.00 ± 0.29 ph(cm² sec)⁻¹, and the gamma-ray emission (excluding the 2.2 MeV line which was appreciably delayed) lagged by less than 20 sec approximately after the hard X-ray and microwave fluxes. We conclude that the “second-stage” acceleration of high-energy solar particles must commence promptly after the impulsive phase.     

Solar maximum mission experiment: Ultraviolet spectroscopy and polarimetry on the solar maximum mission

We describe the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) spacecraft. The instrument, which operates in the wavelength range 1150 – 3600 Å, has a spatial resolution of 2–3 arc sec and a spectral resolution of 0.02 Å FWHM in second order. A Gregorian telescope, focal length 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F₂ waveplates can be inserted behind the spectrometer entrance slit and allows all four Stokes parameters to be determined. The observing modes include rasters, spectral scans, velocity measurements, and polarimetry. Finally, we present examples of initial observations made since launch.