ISRO's Chandrayaan-2 instrument detects hydroxyl, water molecules on the Moon

IIRS collects data from the electromagnetic spectrum obtained from lunar surface which is further used to detect mineral composition

An instrument on the Indian Space Research Organisation's Chandrayaan-2 has detected the presence of hydroxyl (OH) and water molecules (H2O) on the Moon's surface, according to a new paper published in Current Science.

The data was collected by the Imaging infrared spectrometer (IIRS), developed by Ahmedabad-based Space Applications Centre (SAC) of ISRO from the electromagnetic spectrum obtained from the lunar surface, further used to detect mineral composition.

Chandrayaan-2, launched in 2019, suffered a tragic crash in which the lander and rover were completely damaged, however, the orbiter remains active and is now used by scientists to make path-breaking discoveries from the lunar surface.

The instrument can operate between the wavelength of 0.8 to 5 micrometre, which enhances the ability to precisely distinguish between OH (hydroxyl) and H2O (water) molecules.

Chandrayaan-1 of 2008 too had similar equipment called Moon Mineralogy Mapper or M3. However, its wavelength was limited between 0.4 to 3 micrometre. Scientists then had questioned the accuracy of the data received from the instrument, saying it is harder to distinguish OH from H2O in its case.

The paper, authored by scientists from IIRS in Dehradun, SAC in Ahmedabad, UR Rao Satellite Centre and ISRO headquarters in Bengaluru, reveals that the formation of hydroxyl or water molecules occurs due to a process called space weathering, which is when the solar winds blow over the lunar surface. Another reason could be small meteorites interacting with the surface that could result in chemical changes.

The find is also crucial for future planetary exploration for resource utilisation, the paper notes. “The proper interpretation of hydration feature through spectral analysis is significant as it provides important inputs regarding geology and geophysics of the mantle (of the moon) in terms of their mineralogy, chemical composition, rheology and solar–wind interaction."