METEORITES

Evening Star, Issue 21624, 20 January 1934, Page 17

METEORITES

i-tITRAL AUSTRALIAN CRATERS Sir Douglas Mawson proposes, as soon as it is practicable, to take a scientific exploration party to what are known geologically as the Henbury meteoric craters of Central Australia, to the south of the Macdonnell ranges. Sir Edgeworth David, emeritus professor of geology at tho University of Sydney, announcing recently the proposed scientific exploration of the craters, said that last year, on the representations of the Australian and New Zealand Association for tho Advancement of Science, the Federal Government renewed the reserve which it had proclaimed in respect to the area of the twelve nickel-iron Henbury meteorite craters of Central Australia.

The largest of these massive and exceedingly rare meteoric craters is 2Doyds in. diameter and is more than 50ft deep. “ The speed and the force of the great nickel-iron celestial projectile when it struck the earth’s surface at this spot,” said Sir Edgeworth David, “ was so terrific that the rock where it struck, being exceedingly hard and infusible, and a greatly hardened sandstone, or quartzite, was actually fused to a kind of natural slag all round tho edges of the crater through the heat generated by the force of the impact. “ Sir Douglas Mawson, in taking a party to explore the craters scientifically, proposes, in the first place, to determine, by an accurate magnetic survey in the neighbourhood of the largest crater, the depth at which the nickel-iron meteorite that produced it is now lying. Fragments of_ this meteorite are now being investigated by Professor Paneth, of Konigsberg, with a view to determining the absolute time at which tho meteorite_ consolidated. This, of course, has nothing to do with the date of the fall of the meteorite, which, geologically speaking, is obviously recent, for, while there are largo trees growing in the crater, there has not been time, since the fall of the meteorite, for the natural drainage of the country to fill up the crater, although it has to some extent obviously been silted up. “ It has been possible to show that some meteorites must have consolidated nearly 3,000,000,000 years ago_ by applying radio-active methods in this type of investigation, particularly estimating the volume of helium gas enclosed in the meteorite in relation to minute quantities of uranium minerals also present. So far the oldest rocks of the earth tested by similar radioactive methods have proved to be of the order of about 1,600,000,000 years ago. “It is tentatively suggested that these oldest meteorites may be survivals of the original meteorite swarms out of which the earth was formed, giving an age to the earth of approximately 3.000,000,000 years.”