Chapter 2: Energy at the Lunar Surface - Lunar and Planetary Institute

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26 MASS-FREQUENCY DISTRIBUTION Ye R, Distance From Sun (AU) Fig. 2.4. Radial distribution of asteroids (from Dohnanyi, 1972). counts were made of surfaces of different age on the moon. With absolute ages now available for some lunar surfaces as a result of the Apollo program the data will undoubtably lead to a considerable refinement of the large-body flux (Table 2.1 ). The Mass-Frequency Distribution The array of available flux data is both complex and confusing. In almost all cases complex calibrations and corrections are required to convert TABLE 2.1 Determinations of post-mare terrestrial and lunar cratering rate (from Dohnanyi, k972). Number of craters of diameter >l km (km2 109 years) Method Earth Moon Meteorite and asteroid observations 21 x 10-4 12 x 10-4 5 to 23 x 10-4 2 to 9 x 10-4 110 x 10-4 45 x 10-4 Astrobleme counts ii central U.S.A. 1 to 10 x 10-4 0.5 to 4 x 10-4 Crater counts in Canadian shield 1 to 15 x 10-4 0.4 to 6 x 10-4 - Best estimate 12 x 10-4 5 x 10-4
MASS-FREQUENCY DISTRIBUTION observational data to number-frequency equilvalents. In figures 2.5 and 2.6 most of the available data are plottted and it can be seen that in some cases there are differences of several orders of magnitude. A large number of writers have reviewed the literature dealing with the statistics of meteoroid masses (Vedder, 1966 ; Whipple, 1967 ; Bandermann, 1969 ; Bandermann and Singer, 1969; Kerridge, 1970; Soberman, 197 1 ; McDonnell. 1970). Few reviewers have, however, examined the data critically and attempted to establish a best estimate of the flux. The most recent attempt to this end was ~rovided by Gault et al. (1972). All of the micrometeoroid data selected by Gault et al. (1972) were required to fulfill three criteria (Kerridge, 1970). First, the original data must have come from an experiment that gave a positive and unambiguous signal of an event. Second, it was required that the experiment must have recorded sufficient micrometeoroid events to provide a statistically significant result. Third, the response and sensitivity of the sensors must have been calibrated using hypervelocity impact facilities in order to provide, as far as possible, a simulation of micrometeoroid events. Only 10 data points from > Crater Diameter / Particle Mass Calibration D= 7.m11265(cm)(p=3g cm3, v=20km s-1) OGO II, IP: .)r OGO m OHEOS 2 A PIONEER 8 t MARINER IP H Earth Orbiting Station SALYUT MOON, Prehistoric R 0 MARINER 11 , VEXPLORERXXIE 0 EXPLQRER XXI \ PEGASUS r,n,m Particle Mass m (g) Fig. 2.5. Comparison of lunar and satellite micrometeoroid flux data (after H6rz et al., 1973).
Page 1 and 2: CHAPTER 2 Energy at the Lunar Surfa
Page 3 and 4: DISTRIBUTION OF METEOROIDS Heliocen
Page 5 and 6: MEASURING THE METEOROID FLUX Measur
Page 7: MEASURING THE METEOROID FLUX suffic
Page 11 and 12: MASS-FREQUENCY DISTRIBUTION experim
Page 13 and 14: PHYSICAL PROPERTIES Escape Velociti
Page 15 and 16: PHYSICAL PROPERTIES he ratio a/b is
Page 17 and 18: PHYSICAL PROPERTIES r Meteorites I
Page 19 and 20: PHYSICAL PROPERTIES 37 requires pro
Page 21 and 22: HISTORY OF METEOROID FLUX History o
Page 23 and 24: METEOROID ENERGY Solar Flare Track
Page 25 and 26: SOLAR ENERGY 43 radiant energy flux
Page 27 and 28: GRAVITATIONAL ENERGY Fig. 2.16. Enl
Page 29 and 30: GRAVITATIONAL ENERGY Fig. 2.19. Bou
Page 31 and 32: GRAVITATIONAL ENERGY similarly the
Page 33 and 34: GRAVITATIONAL ENERGY Fig. 2.24. Soi
Page 35 and 36: GRAVITATIONAL ENERGY of seismic eve
Page 37 and 38: INTERNAL ENERGY 55 rate proportiona
Page 39 and 40: OTHER ENERGY SOURCES Fig. 2.28. A g
Page 41 and 42: CONCLUDING REMARKS \ Apollo Orbit I
Page 43 and 44: REFERENCES N. H and Ferry, G. W., 1
Page 45 and 46: REFERENCES Mc~onnell, J. A. M., Fla

Chapter 2: Energy at the Lunar Surface - Lunar and Planetary Institute

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