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The reddish color of the Moon, seen in some cities in the South and Southeast regions of the country, may be a consequence of the smoke from the fires that consume the Pantanal and the Amazon. The effect is caused by contact between sunlight and suspended soot particles in the atmosphere.
“For the same reason, the sun has been very red at sunrise and sunset. Have you observed this? Soot”, explained the teacher Dulcide Braz Jr., editor of Tilt’s “Physics in the Vein” column. “When we had giant fires here in Serra da Paulista and Serra do Caracol (MG), the moon was born orange and, even high in the sky, it was still very orange.”
And when is it orange / red?
The orange or reddish color occurs at dusk and dawn, just as we see the sun or the sky at that time. When it rises, the Moon is so close to the horizon that the light reflected by it needs to pass through a thick layer of the Earth’s atmosphere before reaching our eyes, unlike when the satellite appears high in the sky, where the air is weirder. .
When light passes through Earth’s atmosphere, the light reflected by the Moon dissipates through the air. In contact with the gas molecules that make up the air, some colors disperse and become imperceptible. In the case of the Moon (and even the Sun) near the horizon, the denser atmosphere “absorbs” the green, blue and violet colors and only lets through the red tones.
The reddish hue becomes more intense when there are burning particles, volcanic eruptions or pollution in the atmosphere.
Now when it is high in the sky, the reflected light retains its original color, which is white (a combination of all the colors). This is because the thin air at high altitudes makes the loss of blues, greens, and purples small.
It is good to remember that the Moon reflects the white light that comes from the Sun, which is made up of waves of various lengths, therefore made up of various colors. Although our satellite appears very bright, it reflects only 6.7% of the light it receives from the Sun. The brightest parts of its surface are the highest and most cratered regions, made up of rocks rich in calcium and aluminum. The darkest regions are low-lying areas, called ‘seas’, made up of basalt rocks that reflect very little light, hence their grayish color.
The phenomenon was observed in São Paulo (tweet below), in Caxias do Sul, Rio Grande do Sul (photo above) and also in Curitiba, Paraná.
Pantanal is experiencing its worst year in 2020, at least since 1998, when the Inpe (National Institute for Space Research) began monitoring fires in this and other biomes. At the end of September 18,259 sources of fire were identified in the Pantanal, 45.6% more than the 12,536 registered in 2005, the worst so far.
Last month alone there were 8,106 hot spots, the worst September since the start of the all-time series. The previous peak, 3,963, had been recorded in 2004.
In the Amazon, the situation is also worrying: the biome has already registered 76,030 fires in the first nine months of 2020, approaching the 89,176 identified in the last year. In September, there were 32,017, the second worst mark of the decade, only surpassed by 2017 (36,569).
