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Snow falls more than expected on Mars

Snow falls more than expected on Mars

Study of variations in the shadow of large ice masses from seasonal deposits on Mars indicates that the thickness of the accumulated ice is two orders of magnitude greater than estimated.

These blocks are formed by the detachment of broken ice and are located at the foot of steep slopes found in the so-called Arctic Layered Deposits (NPLD). The thickness of the snow and frost accumulated around it varies across the different seasons of the Martian year.

“We suggest using the differences in the shades of these ice masses, “It was discovered in the high-resolution images of HiRISE, an instrument on board NASA’s Mars Reconnaissance Orbiter (MRO), which was launched in 2005,” explains Luisa Lara, researcher at the IAA (Andalusian Institute of Astrophysics)-CSIC and one of the Co-authors of the work published in the Journal of Geophysical Research: Planets.

“Thanks to the amazing spatial resolution of up to 25 cm Through a series of reasonable hypotheses about the distribution of snow and frost around these blocks, we were able to unambiguously relate the length of the ice block’s shadow to its height. This allowed us to estimate the thickness of deposited snow and frost with great accuracy, even at the end of winter and the beginning of Martian spring, when the quality of HIRISE images is not very good,” concludes Pedro Gutierrez, one of the authors of the work and a researcher at IAA-CSIC.

This innovative method was tested on a steep slope located approximately 85.0°N and 151.5°E of Mars’ North Pole. The results showed that the increase in thickness due to the seasonal accumulation of snow and frost may reach 1.6 meters by the end of winter. “Enough to cover a car.”“It then gradually decreases as the red planet moves toward the summer solstice,” noted Haifeng Xiao, a researcher at IAA-CSIC.

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One meter of snow

The contribution of snow alone is about 1 metre. This value is about two times larger than the average thickness predicted by recent snowfall models on Mars, suggesting that local storms associated with large accumulations of carbon dioxide may be more frequent and violent than previously estimated. It should also be noted that this estimate also differs from values ​​previously obtained using the Mars Orbiter Laser Altimeter (MOLA) instrument aboard NASA’s Mars Global Surveyor (MGS) mission. “Although our snow measurement is only on a specific shelf and is averaged across latitudes, this large difference in comparison is really interesting,” says Haifeng Xiao.

Moreover, this new approach allowed us to observe that the contribution of snowfall to the thickness and volume of seasonal snow cover during winter is greater compared to direct surface condensation in the form of frost.

“Last but not least, applying our method to a group of HIRISE images from 2008 to 2021 made it possible to detect annual variations in snowfall thickness. In fact, we show that snow in 2021 reached a depth of about 0.36 meters greater than that measured a decade ago, in 2011,” says Haifeng Xiao.


Like Earth, Mars experiences four seasons throughout the year due to the tilt of its axis of rotation. During the Martian autumn and winter, temperatures in the polar regions can drop below the freezing point of carbon dioxide (about -125 °C), which makes up 95% of the Martian atmosphere by volume. This carbon dioxide can deposit on the surface of the Red Planet either as ice or condense directly into frost.

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Annually, up to a third of atmospheric carbon dioxide is exchanged between the atmosphere and the Martian surface through a seasonal cycle of deposition and sublimation. These seasonal deposits can extend from the poles to approximately 50 degrees latitude.