Mars North Polar Ice Cap Contains Far Less Dust Than Estimated
- Mars’ north polar ice cap contains far less dust than long-standing scientific models estimated, according to a study published in npj Space Exploration.
- Past models established that the top layer of water ice at the Martian north pole contained roughly 25 percent dust by mass, calculated by dividing the mass of...
- The findings provide insight into past Martian climates by illustrating how ice and dust redistribute during major shifts in the planet's axial tilt.
Mars’ north polar ice cap contains far less dust than long-standing scientific models estimated, according to a study published in npj Space Exploration. Researchers recalculated the composition of the Martian surface water ice near the north pole and determined it has a dust-by-mass proportion of about 3 percent, a significant drop from previous estimates of roughly 25 percent.
Recalculating Martian Polar Ice Composition
Past models established that the top layer of water ice at the Martian north pole contained roughly 25 percent dust by mass, calculated by dividing the mass of the dust by the combined mass of the ice and dust. The updated research revised this figure down to about 3 percent by drawing on similar ice-dust research conducted on Earth.
The research team determined that the north pole features a multilayered structure with a cleaner ice layer on top, thinner dust layers just beneath it, and additional ice underneath those strata. To arrive at these measurements, the study combined instrument data and modeling from the Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité spectrometer, the Compact Reconnaissance Imaging Spectrometer for Mars, the Surface Stereo Imager onboard the Mars Phoenix Lander, and known compositions of Martian dust and water ice.
By looking at how the brightness changed over time, we figured out that there is a frost that forms in the winter and it’s more dusty. In the Martian summer it goes away, exposing cleaner, older ice,
said Dr. Aditya Khuller, a senior research scientist at the University of Washington’s Applied Physics Laboratory and co-author on the study.University of Washington’s Applied Physics Laboratory
Implications for Martian Climate History
The findings provide insight into past Martian climates by illustrating how ice and dust redistribute during major shifts in the planet’s axial tilt. Unlike Earth, whose tilt remains relatively stable between 22 and 24.5 degrees over a 41,000-year cycle due to the gravitational pull of the Moon, Mars experiences extreme axial swings ranging from 15 to 35 degrees over periods lasting 100,000 to 1,000,000 years. During periods of low tilt at 15 degrees, polar ice caps expand toward the equator because of reduced sunlight. When the tilt increases to 35 degrees or greater, the polar ice caps shrink or disappear entirely, releasing buried dust into the atmosphere and altering the ice-dust mixture that eventually settles back into the northern latitudes.