NASA scientists have shared the first unmistakable images showing twilight rays and mother-of-pearl clouds painted across the Martian sky. The striking photos appeared on the Curiosity rover team’s social feed, captured as part of ongoing observations from the rover’s skywatching campaign.
Since January 2023, the Curiosity rover has been quietly tracing the behavior of twilight clouds as they drift through Mars’ upper atmosphere. This leg of the mission is slated to wrap up in mid-March, marking a milestone in long-duration atmospheric monitoring. The sunset panorama showcasing sunbeams winnowing through the thin cloud cover is a mosaic created from 28 individual frames, released on March 6. NASA confirmed that these are the clearest sunrays captured on the Red Planet to date.
Twilight rays arrive when sunlight squeezes through gaps between clouds during the moments of sunrise or sunset, long after the star has dipped below the horizon. The optical effect makes it look as if the light converges at a single point behind the cloud, yet the rays actually travel in nearly parallel paths. Researchers say the unusual height and altitude of the Martian clouds provided a perfect stage for this optical phenomenon to unfold, something that Mars enables but Earth generally does not because of atmospheric differences.
On Earth, the visible color of sunbeams during twilight is heavily influenced by the atmosphere, with the sky often turning red or yellow as light scatters. Mars, with its far thinner air, scatters far less light, which keeps twilight rays much whiter and can give Martian sunsets a bluish tinge. This stark contrast helps scientists interpret the unique atmospheric dynamics at play on Mars and informs models of how light interacts with aerosols and dust in the thin air.
In late January, Curiosity also captured a plume of mother-of-pearl clouds during another twilight survey. Such iridescent cloud structures have previously been observed over Earth in polar regions, where extremely cold conditions foster their formation. Known on Earth as polar stratospheric clouds, these features appear in rare, extreme settings, and their Martian counterpart offers a window into the planet’s atmospheric chemistry and thermal structure. The detection strengthens the comparative study of cloud physics between Mars and Earth and raises questions about how aerosols and trace gases influence cloud formation at high altitudes on the red planet.
By watching the color transitions and the timing of cloud events, scientists aim to refine estimates of Mars’ atmospheric composition, particularly the particles and droplets present in the upper layers. Understanding particle sizes helps researchers better simulate how sunlight filters through the atmosphere, which in turn impacts the interpretation of remote sensing data and the planning of future missions that rely on precise atmospheric models. The ongoing twilight cloud observations contribute to a clearer picture of how energy moves through Mars’ atmosphere, how clouds form and dissipate, and how the planet’s climate behaves over seasonal cycles. This knowledge not only informs planetary science but also supports mission design, environmental monitoring, and the broader exploration narrative that seeks to understand Mars’ past and its current atmospheric state. [Attribution: NASA]