ISRO's Chandrayaan-2 orbiter maps abundance of Sodium on the Moon for the first time

The Indian Space Research Organisation’s (ISRO) Chandrayaan 2 Orbiter has mapped the abundance of sodium on the Moon for the first time. This milestone was achieved using the X-ray spectrometer instrument named CLASS onboard the Orbiter which was built at the U R Rao Satellite Centre of ISRO in Bengaluru and provides clean signatures of the sodium line with its high sensitivity and performance.

The need for mapping sodium on the Moon emerged from the lack of information about the element even after analysing the lunar samples brought to Earth during previous missions. 

"Successive laboratory investigations of the returned samples (Apollo, Luna and Chang'E) widened the range of compositions but the fundamental conclusions have remained. However, the returned samples are from a few specific regions of the Moon which do not necessarily represent the global lunar composition," ISRO's statement read. "Sodium is one of those elements that do not have a telltale signature in the visible or near-infrared wavelengths and has thus not been targeted via remote sensing observations."

(Lunar map showing concentration of sodium in different locations; Image: ISRO)

ISRO says that the possibility of mapping the amount of sodium on the Moon was opened up by the Chandrayaan 1 orbiter which detected sodium from its characteristic line in X-rays using the X-ray Fluorescence Spectrometer instrument.

(Illustration of solar wind interaction with sodium atoms; Image: ISRO)

Published in the journal The Astrophysical Journal Letters, the study based on Chandrayaan 2's data suggests that there are two kinds of sodium atoms on the Moon's surface, those that are loosely bound on the surface and those that are part of the minerals. Scientists have found that the loose atoms break away due to the Ultraviolet radiation or the solar wind hitting them and get scattered into the exosphere of the Moon. 

The exosphere is a very thin atmosphere on the Moon which begins at the surface and extends to an altitude of several thousand kilometers. They also concluded that due to the knocking off of the sodium atoms on the surface, they float in space and help in sustaining the exosphere. 

"The new findings from Chandrayaan-2, provide an avenue to study surface-exosphere interaction on the Moon, which would aid development of similar models for Mercury and other airless bodies in our Solar System and beyond," ISRO said in a statement.

Image: Unsplash