Radiation extraterrestrial

When considering how the evolution of life could have come about, the seeding of terrestrial life by extraterrestrial bacterial spores traveling through space (panspermia) deserves mention. Much is said about the possibility of some form of life on other planets, including Mars or more distant celestial bodies. Is it possible for some remnants of bacterial life, enclosed in a protective coat of rock dust, to have traveled enormous distances, staying dormant at the extremely low temperature of space and even surviving deadly radiation The spore may be neither alive nor completely dead, and even after billions of years it could have an infinitesimal chance to reach a planet where liquid water could restart its life. Is this science fiction or a real possibility We don t know. Around the turn of the twentieth century Svante Arrhenius (Nobel Prize in chemistry 1903) developed this theory in more detail. There was much recent excitement about claimed fossil bacterial remains in a Martian meteorite recovered from Antarctica (not since... 

Some radioisotopes are continuously being produced by the bombardment of atoms on the surface of the earth or in its atmosphere with extraterrestrial particles or radiation. One of these is carbon-14, also known as radiocarbon, which is widely used for dating archaeological materials (see Textbox 55). Many radioisotopes that are not primordial or are not created by natural processes are now produced artificially using specialized equipment many of the "artificial" isotopes are of use for probing and analyzing materials. 

The question also arises as to where the chiral molecules came from. Were the L-amino acids or the D-sugars selected on the primeval Earth, or are exuaterresuial sources responsible for the homochirality This second possibility is dealt with by hypotheses on the effect of circularly polarised light, of extraterrestrial origin, on chiral molecules in the molecular clouds from which the solar system was formed. One such hypothesis was proposed by Rubenstein et al. (1983) and developed further by others, particularly A. W. Bonner (Bonner and Rubenstein, 1987) both scientists worked at Stanford University. The authors believe that the actual radiation source was synchrotron radiation from supernovae. The excess of one enantiomeric form generated by this irradiation process would have needed to be transported to Earth by comets and meteorites, probably during the bombardment phase around 4.2-3.8 billion years ago. 

In this article, we first discuss basic dating principles and then studies based on isotopes produced by cosmic radiation in extraterrestrial matter and in the earth s atmosphere. The discussions are intended to illustrate how analytical physical and chemical studies contribute to the understanding of processes in the environmental system and their history. 

The solar constant (intensity of solar radiation outside the Earth s atmosphere at die mean distance between die earth and the sun) has been determined by measurements from satellites and high-altitude aircraft and is 1.353 kilowatts per square meter. This extraterrestrial radiation,... 

The value of 10 is determined by molecular and particulate (cloud and aerosol) scattering, and surface reflection. A small fraction of the molecular scattering is the non-conservative Rotational Raman scattering (RRS) that partially fills the solar Fraunhofer lines in the scattered radiation, creating what is commonly known as the Ring effect [15] As a result, the ratio Iq/F, where F is the extraterrestrial solar flux, contains structure that is correlated with solar Fraunhofer lines. By separating these effects, one can write... 

Guillermo A. Lemarchand, Detectability of extraterrestrial technological activities, http / /www.coseti.org/lemarch 1. htm. See also, Freeman Dyson, Search for artificial stellar sources of infrared radiation, Science 131 1667-1668 (1959) Freeman Dyson, The search for extraterrestrial technology, in Perspectives in Modern Physics (Essays in Honor of Hans Bethe), ed. R. E. Marshak (New York John Wiley Sons, 1966). 

Figure 2. Spectral distribution of scattered solar radiation compared to extraterrestrial and direct solar radiation.

Superherodyne spectrometers are now not common in laboratory microwave experiments, but superheterodyne detection plays a major role in radio astronomy, as we shall see later. The reasons are obvious one cannot modulate the energy levels of extraterrestrial molecules, and a radio telescope collects radiant energy at all frequencies simultaneously. One does not have a primary monochromatic source of radiation, as in laboratory experiments. 

The Earth s elliptical orbit causes the distance between the Earth and the Sun (the Earth s radius vector) to vary by 3.39% from perihelion (closest) to aphelion (farthest). These variations in distance cause the intensity of solar radiation at the top of the atmosphere to vary as 1/R2, where R is the radius vector. Thus the solar input at the top of the atmosphere varies from 1414 Wm 2 (in December) to 1321 Wm 2 (in July). Additional variations in solar intensity, or brightness, result from the solar sunspot cycle, and even solar oscillations. These slight variations in the solar output are usually accounted for in the calculation of solar energy available at the top of the atmosphere, or the total extraterrestrial solar radiation, referred to as ETR. The ETR has only been monitored from space since the early 1970 s, or almost three solar sunspot cycles. Excellent histories of ETR measurements and analysis are provided in Frohlich3 and Gueymard.4... 

Radiometric quantities are important to describe and measure UV and VUV radiation. They are usually subdivided into energetic, spectral and photonic terms. Energetic terms (Tab. 3-9) are based on the energy of the radiation and they refer to all relevant wavelengths. Eor each of these terms a spectral derivative can be defined (Bolton, 1999) which is correlated with a specific wavelength X. Eor example, the extraterrestrial solar spectrum incident on the upper atmosphere is represented by the mean spectral irradiance Eq in W m nm over a defined wavelength interval AX in nm (CIE, 1989). Further, each of the spectral units can easily be transferred to photon-based units, which themselves are related to radio-metric units (cf Braun et al., 1991). 

The concern of cosmochemistry is the investigation of extraterrestrial matter (sun, moon, planets, stars and interstellar matter) and their chemical changes. Meteorites are an object of special interest in cosmochemistry, because of the nuclear reactions induced by high-energy protons in cosmic radiation ( (p) up to about 10 GeV) and by other particles, such as a particles and various heavy ions. Measurement of the radionuclides produced in meteorites by cosmic radiation gives information about the intensity of this radiation in interstellar space and about the age and the history of meteorites. 

I extraterrestrial solar radiation shall be considered to be black body radiation. Under these assumptions determine the emissive power Ms of the sun and its surface temperature Ts. What proportion of the radiation leaving the sun falls within the region of visible light (0.38 fim < A < 0.78 /an) ... 

As a first approach, extraterrestrial solar radiation can be taken to be radiation from a black body at this temperature, see also section 5.3.5. 

Fig. 5.39 Extraterrestrial solar radiation on a surface, whose normal forms the polar angle /3s with the direction of the solar rays...

The large distance between sun and earth means that solar radiation forms a quasi-parallel bundle of rays. The radiation that is not yet weakened by scattering and absorption in the earth s atmosphere is called extraterrestrial radiation. If it is perpendicularly incident on a surface just outside the earth s atmosphere, at a distance r0 = 1 AU from the centre of the sun then the irradiance of the extraterrestrial solar radiation is called the solar constant E0. By evaluating more recent measurements, C. Frohlich and R.W. Brusa [5.33] determined the value... 

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