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1.
A Fekete Gy Rontó M Hegedüs K Módos A Bérces G Kovács H Lammer C Panitz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1306-1310
The main goal of PUR experiment (phage and uracil response) is to examine and quantify the effect of specific space conditions on nucleic acid models. To achieve this an improved method was elaborated for the preparation of DNA and bacteriophage thin films. The homogeneity of the films was controlled by UV spectroscopy and microscopy. To provide experimental evidence for the hypothesis that interplanetary transfer of the genetic material is possible, phage T7 and isolated T7 DNA thin films have been exposed to selected space conditions: intense UVC radiation (lambda=254 nm) and high vacuum (10(-4) Pa). The effects of DNA hydration, conformation and packing on UV radiation damage were examined. Characteristic changes in the absorption spectrum, in the electrophoretic pattern of DNA and the decrease of the amount of PCR products have been detected indicating the photodamage of isolated and intraphage DNA. 相似文献
2.
Els Peeters Nieves Leticia Martín-HernáNdez Nemesio J. RodríGuez-FernáNdez Xander Tielens 《Space Science Reviews》2005,119(1-4):273-292
An overview is given of ISO results on regions of high excitation ISM and gas, i.e. HII regions, the Galactic Centre and Supernova Remnants. IR emission due to fine-structure lines, molecular hydrogen, silicates,
polycyclic aromatic hydrocarbons and dust are summarised, their diagnostic capabilities illustrated and their implications
highlighted.
Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries:
France, Germany, The Netherlands, and the United Kingdom), and with the participation of ISAS and NASA. 相似文献
3.
Michael J. S. Belton Karen J. Meech Michael F. A’Hearn Olivier Groussin Lucy Mcfadden Carey Lisse Yanga R. Fernández Jana PittichovÁ Henry Hsieh Jochen Kissel Kenneth Klaasen Philippe Lamy Dina Prialnik Jessica Sunshine Peter Thomas Imre Toth 《Space Science Reviews》2005,117(1-2):137-160
In 1998, Comet 9P/Tempel 1 was chosen as the target of the Deep Impact mission (A’Hearn, M. F., Belton, M. J. S., and Delamere, A., Space Sci. Rev., 2005) even though very little was known about its physical properties. Efforts were immediately begun to improve this situation
by the Deep Impact Science Team leading to the founding of a worldwide observing campaign (Meech et al., Space Sci. Rev., 2005a). This campaign has already produced a great deal of information on the global properties of the comet’s nucleus
(summarized in Table I) that is vital to the planning and the assessment of the chances of success at the impact and encounter.
Since the mission was begun the successful encounters of the Deep Space 1 spacecraft at Comet 19P/Borrelly and the Stardust spacecraft at Comet 81P/Wild 2 have occurred yielding new information on the state of the nuclei of these two comets. This
information, together with earlier results on the nucleus of comet 1P/Halley from the European Space Agency’s Giotto, the Soviet Vega mission, and various ground-based observational and theoretical studies, is used as a basis for conjectures on the morphological,
geological, mechanical, and compositional properties of the surface and subsurface that Deep Impact may find at 9P/Tempel 1. We adopt the following working values (circa December 2004) for the nucleus parameters of prime importance to Deep Impact as follows: mean effective radius = 3.25± 0.2 km, shape – irregular triaxial ellipsoid with a/b = 3.2± 0.4 and overall dimensions of ∼14.4 × 4.4 × 4.4 km, principal axis rotation with period = 41.85± 0.1 hr, pole directions
(RA, Dec, J2000) = 46± 10, 73± 10 deg (Pole 1) or 287± 14, 16.5± 10 deg (Pole 2) (the two poles are photometrically, but not
geometrically, equivalent), Kron-Cousins (V-R) color = 0.56± 0.02, V-band geometric albedo = 0.04± 0.01, R-band geometric
albedo = 0.05± 0.01, R-band H(1,1,0) = 14.441± 0.067, and mass ∼7×1013 kg assuming a bulk density of 500 kg m−3. As these are working values, {i.e.}, based on preliminary analyses, it is expected that adjustments to their values may be made before encounter
as improved estimates become available through further analysis of the large database being made available by the Deep Impact observing campaign. Given the parameters listed above the impact will occur in an environment where the local gravity is
estimated at 0.027–0.04 cm s−2 and the escape velocity between 1.4 and 2 m s−1. For both of the rotation poles found here, the Deep Impact spacecraft on approach to encounter will find the rotation axis close to the plane of the sky (aspect angles 82.2 and 69.7
deg. for pole 1 and 2, respectively). However, until the rotation period estimate is substantially improved, it will remain
uncertain whether the impactor will collide with the broadside or the ends of the nucleus. 相似文献
4.
Annual solar UV exposure and biological effective dose rates on the Martian surface. 总被引:4,自引:0,他引:4
M R Patel A Bérces T Kerékgyárto Gy Rontó H Lammer J C Zarnecki 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2004,33(8):1247-1252
The ultraviolet (UV) environment of Mars has been investigated to gain an understanding of the variation of exposure throughout a Martian year, and link this flux to biological effects and possible survival of organisms at the Martian surface. To gain an idea of how the solar UV radiation varies between different regions, including planned landing sites of two future Mars surface missions, we modelled the total solar UV surface flux throughout one Martian year for two different dust scenarios. To understand the degree of solar UV stress on micro-organisms and/or molecules essential for life on the surface of Mars, we also calculated the biologically effective dose (BED) for T7 and Uracil in relevant wavelength regions at the Martian surface as a function of season and latitude, and discuss the biological survival rates in the presence of Martian solar UV radiation. High T7/Uracil BED ratios indicate that even at high latitudes where the UV flux is significantly reduced, the radiation environment is still hostile for life due to the persisting UV-C component of the flux. 相似文献
5.
A Lazcano E Díaz-Villagómez T Mills J Oró 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(3):345-356
The most frequently invoked explanation for the origin of metabolic pathways is the retrograde evolution hypothesis. In contrast, according to the so-called "patchwork" theory, metabolism evolved by the recruitment of relatively inefficient small enzymes of broad specificity that could react with a wide range of chemically related substrates. In this paper it is argued that both sequence comparisons and experimental results on enzyme substrate specificity support the patchwork assembly theory. The available evidence supports previous suggestions that gene duplication events followed by a gradual neoDarwinian accumulation of mutations and other minute genetic changes lead to the narrowing and modification of enzyme function in at least some primordial metabolic pathways. 相似文献
6.
López-Valverde Miguel A. Gerard Jean-Claude González-Galindo Francisco Vandaele Ann-Carine Thomas Ian Korablev Oleg Ignatiev Nikolai Fedorova Anna Montmessin Franck Määttänen Anni Guilbon Sabrina Lefevre Franck Patel Manish R. Jiménez-Monferrer Sergio García-Comas Maya Cardesin Alejandro Wilson Colin F. Clancy R. T. Kleinböhl Armin McCleese Daniel J. Kass David M. Schneider Nick M. Chaffin Michael S. López-Moreno José Juan Rodríguez Julio 《Space Science Reviews》2018,214(1):1-31
Space Science Reviews - Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in... 相似文献
7.
8.
The synodic recurrence of the Mt. Wilson plage index (MPSI) and the Calgary cosmic ray (CR) intensity is investigated, using
the wavelet power spectra in the range of 18–38 days, during the last three solar cycles. The unique temporal coincidence
between the quasi–synodic MPSI and the CR periods is detected in 1978–1982 (the 21st solar cycle). In the 22nd cycle there
is a very strong MPSI synodic recurrence, from 1989.5 to 1990.5, but it is absent in the CR data. In 1992.5–1993.5 the MPSI
and CR recurrence phenomenon is in good accordance with the solar wind speed and cosmic ray modulation as measured during
the first Ulysses passage around the Sun. The Gnevyshev gap is present in the 27-day recurrence of CR, in agreement with Kudela
et al. (1999).
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
We present results derived from the analysis of an equatorial streamer structure as observed by the UVCS instrument aboard
SOHO. From observations of the H I Lyα and Lyβ lines we infer the density and temperature of the plasma. We develop a preliminary
axisymmetric, magnetostatic model of the corona which includes the effects of gas pressure gradients on the magnetic structure.
We infer a coronal plasma β > 1 in the closed field regions and near the cusp of the streamer. We add to the model a parallel
velocity field assuming mass flux conservation along magnetic flux tubes. We then compute the Lyα emissivity and the line-of-sight
integrals to obtain images of Lyα intensity, taking into account projection effects and Doppler dimming. The images we obtain
from this preliminary model are in good general agreement with the UVCS observations, both qualitatively and quantitatively.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
The South Pole-Aitken basin region,Moon: GIS-based geologic investigation using Kaguya elemental information 总被引:1,自引:0,他引:1
Kyeong Ja Kim James M. Dohm Jean-Pierre Williams Javier Ruiz Trent M. Hare Nobuyuki Hasebe Yuzuru Karouji Shingo Kobayashi Makoto Hareyama Eido Shibamura Masanori Kobayashi Claude d’Uston Olivier Gasnault Olivier Forni Sylvestre Maurice 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2012
Using Geographic Information Systems (GIS), we performed comparative analysis among stratigraphic information and the Kaguya (SELENE) GRS data of the ∼2500-km-diameter South Pole-Aitken (SPA) basin and its surroundings. Results indicate that the surface rock materials (including ancient crater materials, mare basalts, and possible SPA impact melt) are average to slightly elevated in K and Th with respect to the rest of the Moon. Also, this study demonstrates that K and Th have not significantly changed since the formation of SPA. The elemental signatures of the impact basin of Fe, Ti, Si, O through time include evidence for resurfacing by ejecta materials and late-stage volcanism. The oldest surfaces of SPA are found to be oxygen-depleted during the heavy bombardment period relative to later stages of geologic development, followed by both an increase in silicon and oxygen, possibly due to ejecta sourced from outside of SPA, and subsequent modification due to mare basaltic volcanism, which increased iron and titanium within SPA. The influence of the distinct geologic history of SPA and surroundings on the mineralogic and elemental abundances is evident as shown in our investigation. 相似文献