Matteo Crismani, associate professor of physics and astronomy and director of the Murillo Family Observatory at Cal State San Bernardino, and a team of independent scientists have solved a decade-old Martian mystery that baffled planetary scientists worldwide.

The study, published online in Icarus in September ahead of its appearance in the scientific journal’s January 2026 issue, reexamines a 2015 report that claimed to show massive “plumes” of material extending more than 150 miles above Martian surface — far beyond the planet’s lower atmosphere. In planetary terms, a plume is a broad, feather-shaped cloud of gas, dust, or other material that extends outward from its source. The paper, titled “High-altitude Martian plume is likely an ordinary twilight cloud,” offers a new explanation for the phenomenon.

Crismani is the paper’s lead author, joined by co-authors Michael Chaffin, Kyle Connour, Nicholas Schneider, Shannon Curry, Justin Deighan and Sonal Jain, all from the Laboratory for Atmospheric and Space Physics at the University of Colorado Boulder; Reed Fitzpatrick from the University of California, Riverside; Giuliano Luizzi from the University of Basilicata; Marek Slipski from the Jet Propulsion Laboratory; and Geronimo Villanueva from NASA’s Goddard Space Flight Center. Together, the team collaborated on the new analysis that overturns earlier interpretations of the phenomenon.

“This research brought together scientists from multiple NASA and ESA (European Space Agency) Mars missions, senior and junior researchers, and even an undergraduate contributor,” said Crismani. “It exemplifies the scientific process, where new evidence sparks mystery and debate, yet through collaboration and communication, understanding of complex phenomena can be achieved within our lifetimes.”

Images of Mars
Comparison of old and new analysis methods for suspected Martian plumes. A Hubble Space Telescope observation of Mars from the original Sanchez Lavega et al. (2015) publication (left) is shown in its unaltered form, showing how it might be possible to imagine a high-altitude plume extending far off the Martian disk into space. The same image (right) is shown with an updated latitude and longitude grid, which allows us to determine the edge of the planet (yellow), the boundary between night and day (sunrise, red), and the location where twilight clouds would be illuminated at an ordinary altitude of 50 kilometers (limit of cloud illumination, blue), demonstrating that the suspected plume feature is in fact an ordinary lower atmosphere cloud.

The original 2015 telescopic observations showed patches of light that appeared to rise above the edge of the planet, effectively into space. Since clouds are unlikely to form so high, scientists proposed other possibilities — such as a new type of dust storm or even a daytime aurora. For nearly a decade, the phenomenon remained an unsolved mystery.

Crismani and his colleagues recently reanalyzed the published images of Mars and discovered that it was literally a matter of perspective. The original report had not fully accounted for Earth, Mars and the Sun not being in a straight line. In the new study, careful analysis of the viewing geometry revealed that a small but significant dark crescent was in view, much like Earth’s moon when it is not quite full. This meant that part of Mars' nightside was in view behind the bright patches, but too dark for the telescopes to detect.

“When you notice a pair of eyes gleaming at you out of the darkness, the simplest explanation is that there’s an animal behind them that’s just too shadowy for you to make out, not that there’s a ghost or apparition standing there in defiance of known physics,” said Chaffin. “The same is true of Mars: rather than exotic plumes, simple geometry and ordinary clouds seem to be the cause of these phenomena.”

Once the geometry was verified with computer models, the patches of light were much easier to explain — they were just normal clouds over Mars at sunrise or sunset. When viewed from Earth, the clouds lined up against Mars' dark crescent, creating the illusion that they were impossibly high. But such twilight clouds are relatively common on Mars and have been observed by orbiters and rovers. The team’s analysis confirmed that no new types of clouds, dust storms or auroras are needed to explain the event. 

What once appeared to be clouds in space turned out to be a simple matter of perspective. Mystery solved.