A few centimeters below surface, NASA's Phoenix Mars Lander has found dusty snow. The blue box is ice, while the red box is soil. Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University.
Scientists have discovered ice on Mars in numerous locations over the past two decades. The majority of Martian ice was found using orbital satellites such as NASA's Mars Reconnaissance Orbiter. It is difficult to determine the grain size and the dust content of the Martian ice when it is so far above the surface. These aspects are critical in helping scientists determine the age of the ice and its origin.
Aditya Khuller, a planetary scientist from Arizona State University, and Philip Christensen, an Earth ice expert from Washington, devised a new method to determine how dusty Mars' ice is.
They were able match the brightness of Martian Ice and determine its dust content by combining data from NASA’s Phoenix Mars Lander, Mars Reconnaissance Orbiter, and computer simulations that used computer simulations to predict snow and glacier brightness on Earth. The results were published in the AGU's Journal of Geophysical Research, Planets.
Mars is a dusty planet. Therefore, much of Mars' ice is darker and more dusty than the fresh snow we might find on Earth. The darker and therefore warmer the ice becomes, the more it can affect its stability and evolve over time. This could also indicate that the ice could melt at Mars under certain conditions.
Illustration showing how tiny amounts of Martian dust can affect the brightness and color of Martian snow. The chart's colored lines (blue-red, yellow, and violet) show how dust can reduce the brightness (represented by a black line), to increase the brightness (represented by a grey line). In the black boxes, you can see the simulated "color" for each type of snow/dust. Notice how the color of snow with 0.1% dust appears very similar to the color of pure dust, as is also seen on the Curiosity rover after a dust storm (Right) Credit: NASA/JPL-Caltech/MSSS.
Khuller stated that there is a possibility that the dusty, dark ice could melt down a few centimeters. "Any subsurface liquid water that is produced by melting will be kept from vaporizing in Mars' wispy atmosphere. This will be done by the blanket of ice.
Based on simulations, they believe that the Phoenix Mars Lander's ice was formed from dusty snowfall sometime in the last million years. This is similar to other ice deposits previously found across the mid-latitudes.
NASA's Phoenix Mars Lander has found ice a few centimeters beneath the surface. The blue and red boxes are locations for brightness measurements. Blue is ice, and red is soil. Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University. Blaney et al. 2009
Khuller stated that Mars has been subject to multiple ice ages over its history. "It looks like the ice being exposed at the mid-latitudes of Mars may be a remnant from this dusty snowfall."
The team plans to continue their analysis of ice exposures on Mars and assess if it could melt. They also want to learn more about Mars’ climate history.
The amount of air between snow grains decreases as they get coarser, and the ice becomes darker. This decreases light reflections in the ice, and the likelihood that light is absorbed by it. The brightness of older snow, firn, and glacier ice decreases as the grains grow in size. This makes them appear darker than clean, fresh snow. The right-hand figure shows how the snow's air gradually decreases in size to become firn and then glacier ice. Credit: Mattavelli (2016).
Khuller stated that they are currently developing computer simulations of Martian Ice to examine how it changes over time and whether it may melt to make liquid water. The results of this study will be crucial to our work, as knowing the depth of the ice directly impacts how it heats up.
Explore more Martian gullies may be carved by melting dusty ice
More information: Aditya Khuller et. al., Spectral Albedo of Dusty Martian O Snow and Ice. Journal of Geophysical Research, Planets (2021). Journal information: Journal of Geophysical Research, Planets Aditya Khuller and co, Spectral Albedo of Dusty Martian O Snow and Ice (2021). DOI: 10.1029/2021JE006910.