COVID-19 wrought – and continues to wreak – havoc on the Earth. According to a new study, its effects were not limited to our planet; the surface of the Moon may have been indirectly affected by the resulting lockdown.
At the beginning of the COVID-19 pandemic, before vaccines were developed, lockdowns were used by various governments around the world in an attempt to stop or slow the spread of the disease. At one point, at the beginning of April 2020, around half the world’s population had been ordered to stay at home, or were under some sort of curfew.
This massive change to human life patterns had an immediate effect on wildlife and, of course, our CO2 emissions. Now, thanks to a team investigating lunar night-time surface temperatures, we know that it may have affected the Moon too.
The Moon is tidally locked to Earth, meaning that its rotation speed around its own axis matches the time it takes to orbit around the Earth, and so the near side always faces Earth. The team chose six sites on the surface of the near side, selected to be as flat as possible to limit local effects on temperature as much as possible. Analyzing the Diviner Reduced Data Record from NASA’s PDS Geosciences Node over six years, they found an anomaly.
“Lunar night-time surface temperatures of six different sites on the Moon’s nearside were analysed during the period 2017–2023. Results showed an anomalous dip in the lunar night-time surface temperatures for all the sites during April–May 2020, the strict COVID-19 global lockdown period, when compared to the values of the same period during the previous and subsequent years,” the team explained in their study.
“Since the terrestrial radiation has also showed a significant reduction during that time, the anomalous decrease observed in lunar surface temperatures is attributed to the COVID-19 global lockdown effect. […] The Moon has possibly experienced the effect of COVID-19 lockdown, visualized as an anomalous decrease in lunar night-time surface temperatures during that period.”
Overall, the lunar night temperature difference was around 8–10 Kelvin. The team compared the temperature differences to sunspot activity that could have contributed to such a dip, but found no correlation.
The reason for the dip, according to the team, is the amount of radiation received from the Earth. During the lunar night on the near side, the Moon receives its radiation as it is reflected off the surface of the Earth. As human activities changed, and fewer pollutants were put into our atmosphere, this had a knock-on effect, with less radiation reflected toward the Moon. And so, COVID-19 lockdowns appear to have, inadvertently, briefly made the surface of the Moon colder.
The study is published in Monthly Notices of the Royal Astronomical Society: Letters.
