Magnetic properties of lunar samples.

A breccia sample (10023) from the moon was found to have a strong and fairly stable remanent magnetization. If this sample was not magnetized by local fields in the spacecraft or in the lunar receiving laboratory, it must have been magnetized on the moon. This could have happened in a variety of ways, such as cooling through the Curie temperature, by comitinuous thermal cycling, or by impact, but all of these require the presence ofr a magnetic field. Such a field could have been of internal origin in the moon, or it could have been a residual effect from the earth's magnetic field at a time when the moon and the earth were much closer together. Thermomagnetic studies identify the presence of iron with about 1 percent nickel (igneous). iron with abiout 5 to 10 percent nickel (meteoritic), iron with about 33 percent or more nickel (meteoritic), and ilmenite.

Moon: electrical properties of the uppermost layers.

Presently available data on the electrical conductivity of the uppermost lunar surface layers are in accord with the presence of dry, powdered rocks in which the dielectric loss tangent is frequency-independent over several decades of frequency. These powders have typical direct-current conductivity values of about 10(-13) to 10(-16) mhos per meter and dielectric constants of about 3.0, depending on the packing. Thus the surface layers of the moon are likely to have an extremely low electrical conductivity. At high frequencies normal dielectric losses lead to much higher apparent conductivities that are frequency-dependent.

Stable magnetic remanence in antiferromagnetic goethite.

Goethite, known to be antiferromagnetic, acquires thermoremanent magnetization at its Neel temperature of 120 degrees C. This remanence, extremely stable, is due to the presence of unbalanced spins in the antiferromagnetic structure; the spins may result from grain size, imperfections, or impurities.

Kiaman magnetic interval in the Western United States.

Late-Paleozoic red beds in the western United States indicate that Earth's magnetic field was reversed for a period of the order of 50 x 10(6) years. This finding agrees with similar results from igneous rocks in Australia, indicating, that the long period of reversal in the magnetic field was worldwide. The rocks on the two continents appear to be essentially equivalent in time, suggesting early magnetization of the red beds. The time spectrum of reversals is irregular in geologic time, but present evidence suggests reversals characterized by time scales of 10(4) or 10(5), 10(6), and 50 x 10(6) years. The 50 x 10(6) year period of steady reversed field is found in the late Paleozoic and is termed the Kiaman magnetic interval.