Planetary scientists call the thin gaseous envelope around the Moon as the _______.
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Correct answer: C
Explanation
The correct answer is Option 3 i.e. Lunar exosphere.
- Planetary scientists prefer to call the thin gaseous envelope around the Moon as the 'Lunar Exosphere' because it is so tenuous (having little substance or strength ) that the gas atoms very rarely collide with each other.
- While the Earth’s atmosphere near the mean sea level contains ~1019 atoms in a cubic centimeter of volume, the lunar exosphere contains ~ 104 to 106 atoms in a cubic centimeter.
- Argon-40 (40Ar), which is one of the isotopes of the noble gas Argon, is an important constituent of the lunar exosphere.
- It originates from the radioactive disintegration of Potassium-40 (40K), which has a half-life of ~1.2 × 109 years.
- The radioactive 40K nuclide, which is present deep below the lunar surface, disintegrates to 40Ar, which, in turn, diffuses through the intergranular space and makes its way up to the lunar exosphere through seepages and faults.