On July 4, 2023, the Perseverance Rover celebrated its 842nd Mars Day on Mars. As the red sky above began to darken, the adventure robot aimed its left navigation camera at the hazy horizon.
With one shot, the camera captured a very strange sunset, and all around it the red planet’s sky glowed a strange and brilliant cool blue.
#PerseveranceRover picture taken #Sol842 at 17:04:58.610 with #Navcam #Mars #NASA #Space pic.twitter.com/G1ISGYwbLG
— Mars Mission Image Bot 🤖 (@MarsMissionImgs) 26 September 2023
Pay close attention, because the sunsets you see here on Earth are unlike anything else, and there’s a good reason for that.
Mars is farther from the Sun than Earth, which means the light on its nearest planet is not as strong – at best, Mars receives less than half the sunlight that we do.
Additionally, Mars’ atmosphere only has the same percentage of atmosphere as Earth’s, and it consists mostly of carbon dioxide, with only a small amount of nitrogen and a small amount of oxygen.
This means that sunlight has very different interactions with the atmosphere on the two planets.
Mars at dusk with color processing. (NASA/JPL-Caltech/MSSS/Damia Bouic)
When sunlight enters Earth’s atmosphere, it interacts with oxygen, nitrogen, and other particles in the sky, spreading blue light far and wide.
This is what makes our planet have blue skies during the day. However, when the Sun dips below the horizon or rises above it, its light has more atmosphere to penetrate. This means that most of the blue and purple wavelengths are filtered out by the time the light reaches our eyes, leaving behind the orange and red colors.
On Mars, sunlight does not interact with oxygen or nitrogen, but rather interacts with iron-rich dust hanging in the atmosphere. This ultimately spreads low-frequency red light throughout the sky during the day.
However, at dusk, the red light filters through and the sky glows a cool blue behind the dusty haze.
The differences between the two planets can be seen below.
Difference between Earth (left) and Mars (right) at sunset. (NASA/JPL-Caltech/MSSS/PDS/USGS/Damia Bouic)
“Color [on Mars] comes from the fact that the very fine dust is just the right size so that blue light penetrates the atmosphere a little more efficiently,” explains atmospheric scientist Mark Lemmon of Texas A&M University.
“When blue light scatters from dust, it stays closer to the Sun than light of other colors. The rest of the sky is yellow to orange, because yellow and red light is scattered across the sky instead of being absorbed. or living close to the Sun.”
Because sunlight continually hits dust in the Martian atmosphere, this bluish haze can persist for several hours after sunset or sunrise.
NASA’s Spirit rover photographs a Martian sunset over Gusev crater in 2005. (NASA/JPL)
Dusk on Mars is a great time to take photos of dust and clouds because the light sets against a dark background. Researchers can then use these images to study the composition of the Red Planet’s atmosphere, so they can more easily locate the dust and ice clouds.
Earlier this year, for example, the Curiosity rover captured images of sunlight penetrating twilight clouds in the Martian sky with never-before-seen clarity.
Night-glow clouds on Mars are illuminated by solar flares captured by the Curiosity rover. (NASA/JPL-Caltech/MSSS)
“By looking at color transitions, we see changes in the size of the particles in the cloud,” said atmospheric scientist Mark Lemmon of the Space Science Institute in Boulder, Colorado.
“This tells us about how clouds evolve and how their particle sizes change over time.”
For nearly two decades, sunsets on Mars have been captured by the Curiosity rover, the Perseverance rover, the Spirit rover, and the Opportunity rover.
No matter how much we receive, everything is still amazing.
2023-10-22 02:48:32
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