NASA's Curiosity rover has captured stunning images of iridescent clouds on Mars, tinged with red and green hues, during twilight. These noctilucent clouds, composed of water-ice and carbon-dioxide ice, are observed at high altitudes and exhibit a "mother-of-pearl" iridescence due to sunlight scattering. Curiosity's ongoing observations aim to understand why these clouds are seen in specific Martian regions.
What are these clouds?
- Noctilucent clouds: Also known as "night-shining" clouds, they are high-altitude clouds that appear bright because they're still catching sunlight after the sun has set below the horizon.
- Iridescent clouds: These clouds display a shimmering, rainbow-like effect often referred to as "mother-of-pearl." This iridescence is caused by sunlight scattering off the tiny ice crystals that make up the clouds.
Composition
- Water-ice clouds: These are similar to clouds on Earth and are found at lower altitudes in the Martian atmosphere.
- Carbon dioxide ice clouds: These clouds form at higher, colder altitudes on Mars. Since Mars' atmosphere is over 95% carbon dioxide, these are more common than water-ice clouds at high altitudes.
Why are they only seen at twilight?
- Faintness: Martian clouds are very faint and cannot be seen in the bright daylight.
- Sunlight scattering: The colors and shimmer of these clouds are accentuated when sunlight scatters off them as the sun sets.
Curiosity's Discoveries
- First images of iridescence: In 2019, Curiosity captured the first-ever images of iridescent clouds on Mars.
- Seasonal observations: Curiosity has been observing these clouds every Martian autumn season, providing valuable data about Mars' atmosphere.
- Mystery of location: Scientists are still trying to understand why these clouds are only seen in certain regions of Mars.
Here's a stunning video of these clouds:
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