According to a team of scientists led by Dr Zongcheng Ling of Shandong University in Weihai, the Chinese lunar rover Yutu has found basalts unlike those returned by the American Apollo (1969-1972) and Soviet Luna (1970-1976) missions.
The Chinese lunar rover Yutu, photographed by its lander Chang’e-3, after the lander touched down in Mare Imbrium. Image credit: CNAS / CLEP.
“After some 40 years since the Apollo and Luna missions, China’s Chang’e-3 landing and Yutu rover mission in December, 2013, provided the next robotic in situ measurements on the Moon,” said Dr Ling and his colleagues from the United States and China.
The Chang’e-3 landing site is a relatively fresh impact crater, named Zi Wei crater, in the northern part of the Imbrium basin, a huge impact basin that had been filled by successive lava flows.
“It was a beautiful landing site,” said team member Dr Bradley Jolliff, a researcher at Washington University in St. Louis and a participant in an educational collaboration that helped analyze Chang’e-3 mission data.
During 32 days of surface operations, the Yutu rover traveled 374 feet (114 m) in this region and made four sets of measurements at four locations.
“The basalts at the Chang’e-3 landing site turned out to be unlike any returned by the Apollo and Luna sample return missions,” the scientists said.
The results appear this week in the journal Nature Communications.
“The Apollo and Luna missions sampled basalts from the period of peak volcanism that occurred between 3 and 4 billion years ago,” Dr Ling explained. “But the Imbrium basin, where Chang’e-3 landed, contains some of the younger flows – 3 billion years old or slightly less.”
“The basalts returned by the Apollo and Luna missions had either a high titanium content or low to very low titanium; intermediate values were missing,” he said.
Measurements made by two payload elements of the Yutu rover – the Active Particle-induced X-ray Spectrometer (APXS) and Visible and Near-infrared Imaging Spectrometer (VNIS) – indicated that the basalts at the Chang’e-3 landing site are intermediate in titanium, as well as rich in iron.
Location of the Chang’e-3 landing site: a – Chang’e-1 image with boundaries of typical mare basalt units; b – Chang’e-2 image; c – LROC NAC image; d – the traverse map of the Yutu rover and the locations of APXS and VNIS measurements; e – panoramic view of the Zi Wei crater by the Panoramic Camera on the Yutu rover at the CE3-0008 site. Image credit: Zongcheng Ling et al, doi: 10.1038/ncomms9880.
Titanium is useful in mapping and understanding volcanism on the Moon because it varies so much in concentration, from less than 1% (weight) of titanium dioxide to over 15%.
This variation reflects significant differences in the mantle source regions that derive from the time when the early magma ocean first solidified.
“From a correlated analysis of the regolith derived from rocks at the Chang’e-3 landing site, freshly excavated by Zi Wei crater, we recognize a new type of lunar basalt with a distinctive mineral assemblage compared with the samples from Apollo and Luna, and the lunar meteorites,” Dr Ling and co-authors said.
“The chemical and mineralogical information of the Chang’e-3 landing site provides new ground truth for some of the youngest volcanism on the Moon.”
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Zongcheng Ling et al. 2015. Correlated compositional and mineralogical investigations at the Chang’e-3 landing site. Nature Communications 6, article number: 8880; doi: 10.1038/ncomms9880
