Kamra (1972) presents the data from his field observations of two months. The data taken was potential gradient, space charge, wind speed, and dust particle size. He quotes several sources ( Rudge 1914, Demon 1953, Uchikawa 1951, and Harris 1967 & 1969) for potential gradients in dust storms of -10 kV/m, +15 kV/m, -600 V/m, and -5 kV/m respectively. At a farm near Lubbock, Texas some small puffs or whirls of dust could be seen around the measuring site. Whenever such puffs passed close, potential gradient and space charge generally experienced a negative excursion. On May 2, 1971 near Lubbock, Texas, with wind speeds about 10(+/-5) m/sec , Kamra recorded a potential gradient peak at -90 V/m and with a space charge of +9*10^-3 el/cm^3. The relative humidity was 25% with a temp. of 31.1 deg. C. On May 4, he recorded a period with a potential gradient around -5 kV/m for 8 minutes and a space charge peak of about -45*10^-3 el/cm^3 (wind speed unknown). The wind was blowing 12-17 m/s with a rel. humidity of close to 16%, a temp. of about 33 deg. C., and large amounts of dust were blowing. Measurements were at 1.25 meters above the earth's surface. The area's soil consisted of quartz, feldspar, and clay minerals. In collecting a sample of wind blown dust, the 3 to 200 micron diameter particles were counted. 52% of the particles were 3 microns in diameter. 23% were 5 microns. 10% were 10 microns. 5% were 12 microns. 4% were 20 microns. 3% were 28 microns. 2% were 38 microns. 70 through 200 microns consist of about 3/4%.
Kamra (1989) describes the of amount of point discharge from and charge in dust clouds in India. Charge densities and charge transferred below storms(comparison of dust verses thunderstorms) are given by month for the time period of one year. The point discharge from dust storms is always negative. In one dust storm Kamra recorded a potential gradient of about 1 kV/m and point discharge of about 1.5 to 2 micro amps over a period of one hour. The highest point discharge over a one month period was -32.5 mC.
Anderson (1965) presents observations made off Iceland of the formation of the volcanic island of Surtsey. Potential gradient was measured with an electrometer and a radioactive probe. Measurements were also taken by plane during several flights along the dust cloud. The observations go from November 28 1963 through to about July 1964. The magnitude of the charge created was estimated. At an altitude of 3800 m while flying over the volcano cloud, the vertical component of the electrical field was measured at >110, 15, and 2 V/cm. During the largest eruption they measured point discharge up to about -10 micro amps and potential gradient up to 50 times the undisturbed gradient. In estimating that 0.1 to 0.5 C was neutalized per discharge in the cloud, they inferred a charging current of 30 milliamperes.
Heonig (1975) investigated the electrostatic charging associated with the generation of dust particles. His data indicates that the smallest(one micron) particles are negatively charged. This was observed with EVERY material tested with the exception of magnetite. He suggest that the one micron particles in the Earth's atmosphere are levitated by the electrostatic field of the Earth.
He suggests that low velocity Martian winds move the surface material about and induce electrostatic charging. The laboratory study by H. F. Eden(1973) has indicated that significant charging occurs when a sand/dust mixture is agitated under simulated Martian conditions. With a 1-liter flask containing 50 g of dried sand in an atm of CO2 at 10 mm-Hg, Eden recorded potentials of up to 500 V over 10 cm, which is 5 kV/m.
The fine grain material seen by Viking is estimated to be considerably less than 100 microns(Moore 1977), which is consistent with particles in the atmosphere (Pollack 1977).
In wind tunnel erosion experiments, fine particles apparently aggregated due to electrostatic forces. During these experiments an electrometer gave electrical currents of 2.4 * 10^-9 and 2.5 * 10^-8 A in the impact area. A comparable charge was also observed in wind tunnel simulations for saltating sand grains under simulated Martian conditions. The conclusion is drawn that electrostatic charges occur with both wind blown particles on Earth and simulated Martian conditions and that such charges can hold silt and clay-sized particles together as sand sized aggregates.
Windblown particles my be charged by
Laboratory experiments were conducted on three areas that may effect charge
Greeley also showed that there is a exponential increase in current as the impact velocity is increased. At 10 m/s he recorded a +10^-10 A current compared to a -1.8 * 10^-9 A at 40 m/s. There was also a change from positive to negative current as the velocity increased above about 20 m/s. The particles were approximately 120 micron quartz grains.
Greeley(1980) describes experiments done to try to determine the wind speed on Mars required to cause saltation. He predicts that a wind speed of 25 to 30 m/s for saltation to start. This means that saltation should occur only in the Martian winter.
Greeley(1978) says the estimated particle size for dust storms is a few microns or less (Pollack 1977).
They suggest palagonite is a good analog to the soil of Mars in composition, particle size, spectral signature, and magnetic properties.
The bulk of surface fines in landing areas are between 10 and 100 microns (Hargraves et al. 1976). Pollack et al. (1979) suggest 2.5 microns for rep. particle size for dust in large storms.
References
Kaska(1980) deals with triboluminescence from mobile fractures in crystals. The authors created the fractures by impact of a piston. In crystal fractures the movement of cracks and sudden creation of new surfaces causes TL. The article focuses on organic molecules. It looks at force and compression verses TL.
Lahav(1982) shows the results of experiments on the amount tribo- luminescence and its decay rate in several clays. It was noted that,"a surprisingly high photon flux continues, although at a diminishing rate, for several days." The experiment induced TL by mortar/pestle or hammer, or by freezing by either -10 degree C salt-ice or liquid nitrogen. Montmorillonite was shown to produce luminescence under all of the listed methods. Previously Coyne(1981) say that the freezing and drying of montmorillonite showed luminescence.
According to Zink(1978), there are eight ways for TL to occur(in roughly decr. order): crystal florescence, crystal phosphorescence, luminescence from nitrogen or other gases, metal-centered luminescence, luminescence from charge-transfer complexes, and single examples of luminescence from free radicals and possibly blackbody radiation and conduction-band to surface-band transitions. The mechanical energy can come from anisotropic pressure by grinding or crushing crystals, motion of a fluid over surface of a solid, thermal shock, and rapid crystallization. Two hard objects struck together or frictionally heated and electrical arcing from static electrification by rubbing dissimilar objects are referred to as trivial forms of TL.
In the section on mechanical aspects of TL, there are three mechanisms of triboexcitation discussed: electrical, thermal, and chemical. The proposed electrical mechanisms include: piezoelectric effects, frictional electrification from dissimilar materials, and electrification within crystals from shear, cleavage, or rupture of crystal. The results were that piezoelectric and frictional electrification were not of primary or general importance. In crystal fracture intensity seemed to depend on new surfaces created by fracture. It is noted that some worker believed that TL can be excited by plastic deformation.
Toulmin's ( 1977) normative calculations, comparisons with reference libraries have led to a qualitative mineralogical model in which the fines consist largely of iron-rich smectites (or their degradation products), carbonates, iron oxides, and sulfate minerals.
From lander samples - TABLE 1
Material aprox ave Est abs err (% by wt)
-------- --------- -----------
SiO 44.0 5.3
2
Al O 5.6 1.7
2 3
Fe O 18.8 2.9
2 3
MgO 8.5 4.1
CaO 5.4 1.1
K O <0.3 ...
2
TiO 0.9 0.3
2
SO 8.3 1.2
3
Cl 0.8 0.3
Possible but not in the equipment's detection range H O,CO ,Na(NaO ),and NO .
(the first two are most likely) 2 2 2 x
(Reference: Toulmin, 1977, Fig. 1, p. 4628) "Note should be taken of the work of Hunt et al. [1973] and Logan et al. [1975], who interpreted certain features of the infrared spectra of the Martian dust cloud ... as indicative of montmorillonitic clay particles as a major component of the dust." On other part of the composition Toulmin's and Hunt/Logans' interpretations differ.
" Computer Searches for Matches The best fits include mafic and ultra mafic rocks, amphiboles, some lunar rocks, a few analyses of meterites esp. carbonaceous chondrites, and some Fe-rich clays. Fe-rich montmorillonites are generally good matches for most elements except S, suggesting that such materials may be a major component of the mixture of material analyzed. "
Computer Generated Mixture of matching soil - TABLE 2
Table from Baird et al. [1976]
Composition, wt %
Nontronite 47
Montmorillonite 17
Saponite 15 This is off by aprox. 4% in proportions
Kieserite 13 of chemical content from one of the
Calcite 7 martian samples.
Rutile 1
(Reference:Toulmin, 1977, Table 4, p. 4631.)
From summary:
Carr(1981) stated that with the telescopic reflection spectra of Mars bright regions, the best fitting terestial material is palagonite, a largely amorphous reaction product of basltic lava with water. On the otherside, according to A. Bonin, Fe-rich clays fit with the results of the Viking biology experiment.
Attempts to match telescopic reflectance spectra of Mars have shown Mars spectra to be inconsistent with ferric oxides or iron-bearing clays.
Bonin(Hewbrew Univ., Isreal) reported work on simulation of the results of the Viking biology experiement. He showed that Fe-rich clays can catalyse decarboxylation and/or oxidation of organic acids and was able to reproduce accurately the Viking labelled release results. Fe-rich clays were also used successfully to simulate the gas exchange and pyrolitic release experiments.
(McCord, Univ. of Hawaii) The differences were attributed to rock-soil mixes and condensates and tentative correlations of R-V units with units identified from telescopic spectra, mostly resemble those of oxidezed basalts, were made.
In comparing the infrared spectum of the Mariner 9 dust storm with Quartz, Mica, and Anorthosite, Aronson's (1975) best match came from a mixture:
Mica 4 microns,(0.8 mircon thickness) 1.5/cc; Anothosite 1 micron,
50/cc; Quartz 2 microns, 3/cc.
^ Particle size.
^Not very conclusive!^
Hunt (1973) shows that in the infrared spectum, montmorillonite is a good
match to the dust cloud observed by Mariner 9 in 1971. Of the substances
compared, montmorillonite was the best match.
Binder(1977) quoted Moore(1977) as saying the sight contains abundant
fine-graded (<100 micron) material. He then suggested the rocks and sand have
limonite stains (FeO,OH,nH O).
2
From available data Singer(1987) says Mars has two type of material: bright,
heavily altered and dark, less altered material. The aerosol dust is composed
of brightest and redest material. The brighter areas have a larger amount of
ferric iron (Fe^3+). Their suggestion of a spectral analog is a subset of the
group known as palagonite. The Martian soild may be better crystalline than
terrestrial palagonite. The conclusion they draw from their data: Either 1) crystalline clays are a minority phase mixed with other materials (e.g. palagonite), or 2) the bright soils are homogeneous but structurally intermediate between amorphous palagonites and crystalline clays.
A very rough estimate for the corbonate in the in the regolith is a few weight percent if it is uniformly distributed.
According to Coyne(1987) clays have a number of special properties which would suggest their capacity to store significant amounts of electronic energy that may affect both the reflectance properties of the clays and their surface reactivity, particularly in the presence of penetrating radiation or mechanical and frictional stresses. (From Coyne, L.M.,Origins of Life, 1985)
As much as 33% of the Martian surface iron could be accomodated in clays. Iron as a surface constituent of a clay produces catalytic activity(for the decompostion of organic acids) which fits better than palagonite with the Viking data.
Coyne talks about preparing a typical sample of montmorillonite clay using the Banin method (Banin, 1973).
Clark(1987) believes that the composition is consistant with SNC meteorites and related theoretical materials.
Walsh(1987) feels that regardless of of what the products of weathering on Mars are, they may still be mixed in a matrix of palgonite. Palagonite is the clossets known spectral analog of Martian dust and soil. Note: Get final report.
Ultra Mafic Intermediate Silicic
Mafic
Largely - - - - - - - - - - - - - - Largely
Fe Mg Si,Na,Al
Si Al Fe Mg O (OH) Ca Na K (Pala #3)
3.46 .93 .9 .30 10 2 .34 .05 .02
Si Al Fe Ti Mg O (OH) Ca Na K
3.46 .93 1.15 .14 .30 10 2 .34 .05 .02