Moon Rock Mineral Found In Australia
When the Apollo 11 astronauts returned to Earth in July 1969, they brought with them moon rock samples containing a mineral geologists had never seen before. This unusual silicate of iron, silicon, oxygen, titanium, zirconium, and traces of yttrium, uranium, and other rare earth elements was named tranquillityite after the Mare Tranquillitatis - the site of the first moon landing. The mineral had never been seen before in any terrestrial rock, and was believed to be unique to the lunar surface.
That is, until now.
According to a new paper authored by geologist Birger Rasmussen of Curtin University in Bentley, Australia, tranquillityite has been found in igneous rock at six sites in Western Australia. This surprising finding suggests that this formerly lunar mineral may be more common on Earth than scientists previously thought.
The tranquillityite inclusions were found in dikes and sills - volcanic intrusions into existing sedimentary rock - dating back to the Proterozoic and Cambrian ages, some one billion to 500 million years ago. The needle-shaped tranquillityite crystals were smaller than the width of a human hair and were identified by the signature scattering pattern they produced when hit by a blast of electrons.
Although the mineral has no real monetary value, it could be very useful to geologists for the trace amounts of uranium it contains, which can be used for uranium-lead radiometric dating. The samples found by Rasmussen's team were used to precisely date the surrounding sedimentary rocks in which they were found.
This discovery marks the third instance of a lunar mineral later being found in terrestrial sources. The titanium-rich armalcolite and the iron silicate pyroxferroite had previously been thought unique to the Moon when they were first brought back to Earth by the Apollo missions, but have since been found in mines and quarries here on Earth. Tranquillityite had reigned for more than 40 years as the sole lunar mineral that had never been found in terrestrial rocks.
Lead author Rasmussen suggests several reasons for the four-decade delay in finding this ancient mineral. Tranquillityite, with the chemical formula (Fe2+)8Ti3Zr2 Si3O24, is formed under rare conditions during the crystallization of molten rock. It is also unstable over geologic time periods due to water, oxygen, erosion, tectonic activity, and absorption by living organisms.
Another more practical reason it hadn't been found, says Rasmussen, is that geologists weren't really looking for it. While the moon rock samples have been analyzed in excruciating detail over the past 40 years, terrestrial rocks are rarely subjected to the same level of scrutiny. These new findings suggest that this rare moon mineral is not nearly as rare as geologists previously thought.
- Rare Moon Mineral Found on Earth - ScienceNOW
Rare Moon Mineral Found on Earth - ScienceNOW
- Third lunar mineral - Tranquillityite found in Western Australia
(PhysOrg.com) -- Back in the heyday of the Apollo moon program, hundreds of pounds of rock samples were carted back to Earth by visiting astronauts. Those samples were then pored over more thoroughly by geologists than perhaps any other rocks in huma
- Tranquillityite: The last lunar mineral comes down to Earth,
Geology, v. 40 no. 1 p. 83-86.First published online November 23, 2011, doi: 10.1130/G32525.1