A joint research team led by Profs. LIN Yangting and LIN Honglei from the
Institute of Geology and Geophysics of the Chinese Academy of Sciences
(IGGCAS) observed water signals in reflectance spectral data from the lunar
surface acquired by the Chang'E-5 lander, providing the first evidence of
in-situ detection of water on the Moon.
The study was published in Science Advances on Jan. 7.
Researchers from the National Space Science Center of CAS, the University of
Hawaiʻi at Mānoa, the Shanghai Institute of Technical Physics of CAS and
Nanjing University were also involved in the study.
Many orbital observations and sample measurements completed over the past
decade have presented evidence for the presence of water (as hydroxyl and/or
H2O) on the Moon. However, no in-situ measurements have ever been conducted
on the lunar surface.
The Chang'E-5 spacecraft landed on one of the youngest mare basalts, located
at a mid-high latitude on the Moon, and returned 1,731 g of samples. Before
sampling and returning the lunar soil to Earth, however, the lunar
mineralogical spectrometer (LMS) onboard the lander performed spectral
reflectance measurements of the regolith and of a rock, thereby providing
the unprecedented opportunity to detect lunar surface water.
Water (OH/H2O) can be detected using spectral features at ~3 μm. However,
above 2 μm, thermal emission from the hot lunar surface will significantly
modify and mask spectral features.
Therefore, the researchers used a thermal correction model to correct the
LMS spectra. Following this correction, the undoubted spectral absorptions
at 2.85 μm were observed at the Chang'E-5 landing site.
The quantitative spectral analysis indicates that the lunar soil at the
landing site contains less than 120 ppm of water, which is mostly attributed
to solar wind implantation. This is consistent with the preliminary analysis
of the returned Chang'E-5 samples.
In contrast, a light and vesicular rock that was also analyzed exhibited
much stronger absorption at 2.85 μm, corresponding to an estimated ~180 ppm
of water, thus suggesting an additional water source from the lunar
interior.
The results of compositional and orbital remote sensing analyses show that
the rock may have been excavated from an older basaltic unit and ejected to
the landing site of Chang'E-5. Therefore, the lower water content of the
soil, as compared to the higher water content of the rock fragment, suggests
that degassing of the mantle reservoir beneath the Chang'E-5 landing site
took place.
This discovery is consistent with the prolonged volcanic eruptions in the
Procellarum KREEP (potassium, rare earth elements, phosphorus) Terrain
region, and also provides vital geological context for the analysis of the
returned Chang'E-5 samples.
This work was supported by the Strategic Priority Research Program of CAS,
the Key Research Program of Frontier Sciences of CAS, the Key Research
Program of IGGCAS and the National Natural Science Foundation of China.
Reference:
In situ detection of water on the Moon by the Chang’E-5 lander by
Honglei Lin, Shuai Li, Rui Xu, Yang Liu, 7 January 2022, Science
Advances.
DOI: 10.1126/sciadv.abl9174
Tags:
Space & Astrophysics