Bengaluru: isro He said on Tuesday that the mass spectrometer aboard the Chandrayaan-2 orbiter, ChandraAtmospheric Composition Explorer 2 (CHACE-2) made its first observations of the global distribution of argon-40 (a noble gas) in the outer atmosphere of the Moon.
“These observations provide insight into the species dynamics present in the lunar exosphere, as well as radioactive activities in the first tens of meters below the lunar surface,” Isro said.
Isro noted that the noble gases act as important tracers for understanding the interaction processes between the surface and the exosphere, and said that argon 40 (Ar-40) is an important trace atom for studying the dynamics of species in the moon’s exosphere.
Ar-40 arises from the radioactive decay of potassium-40 (K-40) found below the surface of the Moon. Once formed, it spreads through the intergranular space and makes its way into the outer shell of the Moon through seeps and fissures.”
The uniqueness of this result from Chandrayaan-2 lies in the fact that although the Apollo-17 and LADEE missions have detected the presence of Ar-40 in the moon’s exosphere, measurements have been limited to the subtropical region of the moonIsro said the new findings were published in the journal Geophysical Research Letters.
“Because there is a sharp latitude temperature gradient on the lunar surface, it has so far been a hiatus region for studying the global dynamics of lunar exosphere species, a heat-driven process. In this context, CHACE-2 observations on Ar-40 play into even latitude regions. Central (60° to +60°) played an important role in bridging the knowledge gap,” Isru said.
Observations of CHACE-2 reveal an increase in Ar-40 density near the sunrise separator, a decrease during the day side, a secondary peak near the sunset separator, and a minimum on the night side – a typical behavior of a condensable gas.
“…the CHACE-2 observations provide the diurnal and spatial variability of Ar-40 covering the regions of the moon’s equator and midlatitude,” Esro added.
Also, for the mid-latitudes, the CHACE-2 observations showed for the first time that the variance in the density of the Ar-40 number with respect to solar longitudes is similar to that of the low-latitudes, despite the differences in temperature and topography.
CHACE-2 observations reveal that the Ar-40 distribution has significant spatial heterogeneity. There are localized improvements (termed argon swelling) over several areas including KREEP (potassium (K), rare earth elements, and phosphorous (P)) and the Antarctic-Aitken topography,” Isro said.
Argon swelling observations are indicative of unknown or additional loss processes, moon earthquakes or regions with lower activation energies, which require a better understanding of the outer shell interactions and source distributions of Ar-40, Isro added.
CHACE-2 was a sequel to CHACE An experiment on the Moon Impact Probe (MIP) for the Chandrayaan-1 mission also drawn from the Mars Extra Atmospheric Neutral Composition Analyzer (MENCA) experiment aboard the Mars Orbiter Mission (MOM).
“These observations provide insight into the species dynamics present in the lunar exosphere, as well as radioactive activities in the first tens of meters below the lunar surface,” Isro said.
Isro noted that the noble gases act as important tracers for understanding the interaction processes between the surface and the exosphere, and said that argon 40 (Ar-40) is an important trace atom for studying the dynamics of species in the moon’s exosphere.
Ar-40 arises from the radioactive decay of potassium-40 (K-40) found below the surface of the Moon. Once formed, it spreads through the intergranular space and makes its way into the outer shell of the Moon through seeps and fissures.”
The uniqueness of this result from Chandrayaan-2 lies in the fact that although the Apollo-17 and LADEE missions have detected the presence of Ar-40 in the moon’s exosphere, measurements have been limited to the subtropical region of the moonIsro said the new findings were published in the journal Geophysical Research Letters.
“Because there is a sharp latitude temperature gradient on the lunar surface, it has so far been a hiatus region for studying the global dynamics of lunar exosphere species, a heat-driven process. In this context, CHACE-2 observations on Ar-40 play into even latitude regions. Central (60° to +60°) played an important role in bridging the knowledge gap,” Isru said.
Observations of CHACE-2 reveal an increase in Ar-40 density near the sunrise separator, a decrease during the day side, a secondary peak near the sunset separator, and a minimum on the night side – a typical behavior of a condensable gas.
“…the CHACE-2 observations provide the diurnal and spatial variability of Ar-40 covering the regions of the moon’s equator and midlatitude,” Esro added.
Also, for the mid-latitudes, the CHACE-2 observations showed for the first time that the variance in the density of the Ar-40 number with respect to solar longitudes is similar to that of the low-latitudes, despite the differences in temperature and topography.
CHACE-2 observations reveal that the Ar-40 distribution has significant spatial heterogeneity. There are localized improvements (termed argon swelling) over several areas including KREEP (potassium (K), rare earth elements, and phosphorous (P)) and the Antarctic-Aitken topography,” Isro said.
Argon swelling observations are indicative of unknown or additional loss processes, moon earthquakes or regions with lower activation energies, which require a better understanding of the outer shell interactions and source distributions of Ar-40, Isro added.
CHACE-2 was a sequel to CHACE An experiment on the Moon Impact Probe (MIP) for the Chandrayaan-1 mission also drawn from the Mars Extra Atmospheric Neutral Composition Analyzer (MENCA) experiment aboard the Mars Orbiter Mission (MOM).
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