Discovery of a new lunar material explains weathering on the moon, the University of Tennessee geologist who helped find it said Friday.
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Dr. Larry Taylor
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Dr. Larry Taylor, professor and director of UT’s Planetary Geosciences Department, and four other scientists identified the mineral in a lunar meteorite found in Oman.
The material, named hapkeite, is unlike anything found on earth, Taylor said.
Identification of the new mineral was reported in the journal Proceedings of the National Academy of Sciences.
Named for the scientist who 30 years ago predicted the space weathering process that forms this mineral, hapkeite is an iron-silicon compound formed by the constant bombardment of tiny meteorites into the moon’s surface.
“The moon is a very hostile place,” Taylor said. “It is constantly being struck by meteorites because it has no atmosphere to protect it like we have on earth.”
Most of the projectiles that hit the moon are so small they are not visible to the naked eye, Taylor said. Because the meteorites are traveling at speeds unknown on earth, their impact generates heat that melts silicate soil particles, Taylor said.
Vaporization of portions of the melted material condense into elemental iron, a silica-rich gas and hapkeite, which has two atoms of iron and one of silicon. Taylor said iron-silicon materials are sometimes created by lightning strikes on earth, but hapkeite has a different origin and structure.
Weathering on Earth occurs through the action of wind, water and chemical processes. Since the moon has none of these, the weathering of lunar rocks had to explained differently, he said.
The major space weathering on the moon is due to the impacts of meteorites and micrometeorites, Taylor said.
“Bruce Hapke of the University of Pittsburgh said 30 years ago that the heat from micrometeorites was creating a vaporization which was forming new minerals on the moon. It is fitting that we name the new mineral for Bruce.”
Taylor, who has worked with lunar samples since the Apollo astronauts first collected them 35 years ago, is now checking some of those lunar soil grains for hapkeite.
The meteorite used for confirming the presence of hapkeite was found in January 2000 in the Dhofar region of Oman. The deserts of the Middle East and polar ice caps are the best sources of meteorites because the charred rocks are easier to spot against light-colored sand or ice, he said.
Mahesh Anand worked with Taylor at UT as a post-doctoral fellow on the hapkeite project. Scientists from Russia’s Vernadsky Institute of Geochemistry and the Geophysical Laboratory of the Carnegie Institution in Washington also participated.