New Delhi: A series of Coronal Mass Ejections (CMEs) resulted in the strongest geomagnetic storm seen in two decades in May last year. The charged plasma clouds launched outwards from the Sun interacted with each other in interstellar space, having an impact on all the worlds across the Solar System. ISRO’s Aditya L1 and Chandrayaan spacecraft both observed the impact of the extreme space weather event, and now the study by ISRO scientists on the Chandrayaan 2 observations has been published in Geophysical Research Letters. The study is the first observational confirmation that solar outbursts inflates the exosphere or outer atmosphere of the Moon.
The Chandra’s Atmospheric Composition Explorer 2 (CHACE-2) instrument on board the Chandrayaan 2 orbiter showed an increase in the total pressure of the lunar atmosphere on the day side, or the side facing the Sun. Such an effect was previously predicted in theory, but has not been directly observed. The injection of heat into the atmosphere of the Earth by solar outbursts causes it to inflate too, resulting in increased drag on satellites in Earth orbit. The Moon has a tenuous, rarified atmosphere through, with the gas atoms and molecules rarely interacting. The exosphere of the Moon is extremely sensitive to solar activity.
The tenuous lunar exosphere
The lunar atmosphere is formed by a number of processes, including meteorites impacting the lunar surface, the plasma wind streaming out of the Sun, and the effect of light from the Sun on the lunar surface. The increased solar activity enhanced the process of atoms getting knocked off the lunar surface, resulting in the increase in the pressure of the lunar exosphere. The observations improve the scientific understanding of the Moon and the influence of space weather events. The findings have implications for the construction of future lunar habitats, that need to be adequately fortified against such extreme space weather events.