A recent study has uncovered a remarkable effect of the Earth’s Covid-19 lockdown on the Moon. Indian researchers analysing lunar night-time temperatures between 2017 and 2023 discovered an unexpected dip in surface temperatures during April-May 2020, coinciding with the strict global lockdowns. The findings suggest that the drastic reduction in human activity on Earth, which significantly affected the planet’s radiation output, may have also impacted the Moon's surface temperature.
The research was conducted by K Durga Prasad and G Ambily from the Physical Research Laboratory (PRL), Ahmedabad, and they analysed data from NASA's Lunar Reconnaissance Orbiter for six different sites on the rear side of the Moon to study the temperatures.
According to the study published in peer-reviewed 'Monthly Notices of the Royal Astronomical Society: Letters', the lunar surface temperature during night-time is sensitive to Earth's radiation, known as terrestrial radiation (TR), which plays a critical role in influencing the Moon’s thermal environment. During the day, the Moon receives both solar radiation and TR, but at night, Earth’s radiation is the sole source of external heat. The lockdown, which led to reduced greenhouse gas emissions and decreased pollution, resulted in a significant reduction in TR, contributing to the dip in lunar night-time temperatures.
Analysing the six different sites on the Moon’s nearside using data from LRO, the researchers found a clear temperature drop during the peak of the global shutdown compared to the same periods in previous and subsequent years. They noted a 8-10 Kelvin drop in the temperatures on the lunar surface at the six sites.
The study argues that this decrease is directly tied to the decline in TR caused by the widespread halt in industrial and human activities during the lockdown.
The Diviner RDR data used for the work is available in public domain.
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'May Never Occur Again'
This discovery marks the first time that a significant event on Earth has been observed to have a measurable impact on the Moon. The study suggests that lunar night-time temperatures could serve as a potential indicator for studying Earth’s climate changes in the future. Observing the Moon's surface temperatures, particularly in the absence of solar radiation, could provide insights into fluctuations in Earth's radiation budget, which is increasingly influenced by human-induced climate change.
“...we have utilized a rare and unique opportunity of COVID-19 to carry out our study, which may never occur again,” the researchers noted in the study report.
The study emphasises the Moon’s potential as a stable platform for monitoring Earth's environmental changes. Further exploration using Moon-based observatories could provide more precise data and help scientists better understand the long-term impacts of human activity on Earth’s climate system.
The researchers also said the results can be substantiated further in future from Moon-based observatories, thus making them potential tools to observe the environmental and climate changes on Earth.
The team acknowledged the support their got from the Department of Space for their research, and said part of the work was carried out under the DST-INSPIRE fellowship grant given by the Government of India.