Universe Today
The planet Mars is known for its massive dust storms, dust devils, and two large polar ice caps, with its north polar cap being one of the Red Planet’s most striking features. Comprised of water ice, the north polar cap not only holds potential for being a source of water for future human missions, but it also helps researchers’ piece together past climates on Mars. But an ongoing debate within the scientific community is the ice-dust relationship at the north polar cap, specifically how much dust comprises the north polar cap compared to the much larger amount of water ice.
Now, a pair of researchers might have inched closer to better understanding the Martian north polar ice cap ice-dust layer relationship. As discussed in a recent study published in npj Space Exploration, the researchers revealed new evidence that the Martian surface water ice near the north pole could be far less dusty than longstanding models had previously estimated. Past studies have modeled the top layer of north pole water ice could contain a dust by mass of about 25 percent, with dust by mass being the proportion of a material’s total weight that contains dust. Essentially, it’s calculated by dividing the mass of the dust by the total combined mass of the ice and dust.
New ice-dust measurements
However, this new study has redone these calculations based on similar ice-dust research on Earth, with the researchers providing a new estimate that the top layer of north pole water ice contains a dust by mass of about 3 percent, far lower than the previous estimate of 25 percent. They note the reason behind this is the north pole contains a multilayered mixture of ice on top with thinner dust layers just beneath it, followed by ice beneath that.
They came to this estimate by using a combination of instrument measurements and modeling, including the Observatoire pour la Minéralogie, l’Eau, les Glaces et l’Activité (OMEGA) spectrometer, the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), the Surface Stereo Imager (SSI) onboard the long-retired Mars Phoenix Lander, and known compositions of water ice and Martian dust.
“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, who is a senior research scientist at the University of Washington’s Applied Physics Laboratory and co-author on the study.
Mars’ whacky climate shifts
The implications for this study go far beyond present-day ice-dust layering and even goes far back in time with the goal of gaining insight into past climates on Mars. This is because while Earth’s tilt is stable due to the gravitational tug from our Moon, Mars lacks this tilt stability. As a result, while Earth’s tilt wobbles like a spinning top only a few degrees from about 22 to 24.5 degrees over a 41,000-year cycle, Mars’ tilt experiences far larger swings, ranging between 15 to 35 degrees between 100,000 to 1,000,000 years. When this happens, drastic climate shifts occur, including redistribution of ice and dust across the planet, and specifically the northern latitudes.
Illustrated diagram depicting how changes in Mars' axial influences the polar caps and climate. (Credit: NASA/JPL-Caltech)
For example, during periods of low tilt (15 degrees), the polar ice caps expand in size, almost down to the equator, due to the lack of sunlight striking their locations. In contrast, during periods of high tilt (35 degrees or greater), the polar ice caps decrease in size, often completely disappear and reappear at other surface locations. When this happens the dust that was buried beneath the ice layers get distributed throughout the atmosphere, creating this ice-dust mixture that gets dump back down into the northern latitudes. It goes without saying that Mars’ climate is crazier than Earth’s so studies like this help piece together how this ice-dust layering could she new light on past Mars climates.
What new insights into Mars’ north polar ice and dust will researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
