MARS MRO Image: North Pole Weather forecasts

In winter a layer of frozen carbon dioxide covers the Martian North Pole. 

Approximately 50 percent of this ice cap falls to the ground as snow. 

This image was taken by NASA's Mars Reconaissance Orbiter (MRO) in 2006. 

Credits: NASA

In the north of the red planet snowfalls occur with great regularity.

Expeditions of Mars rovers into this region could therefore be easily planned.

Snowstorms lashing down at the northern hemisphere of Mars during the icy cold winters may be predicted several weeks in advance, say researchers from the Tohoku University in Sendai (Japan) and the Max Planck Institute for Solar System Research (MPS) in Katlenburg-Lindau (Germany) in their newest publication.

For the first time, the scientists' calculations show a connection between these snowfalls and a special Martian weather phenomenon: fluctuations of pressure, temperature, wind speeds, and directions that in the northern hemisphere propagate in a wave-like manner and occur very regularly.

For missions to the red planet exploring this region with rovers, such weather forecasts would offer the possibility of choosing a route that avoids heavy snow storms.

The Martian polar regions are an icy cold world. Similar to those on Earth they are covered by cohesive ice caps. In winter, when the temperatures drop below -128 degrees Celcius, this layer of ice is mainly supplied by frozen carbon dioxide from the atmosphere.

The ice caps then cover a region reaching south to about 70 degrees northern latitude. Only in the comparably warm Martian summer the carbon dioxide sublimates revealing the planet's eternal ice: a considerably smaller cap of frozen water.

Dr. Paul Hartogh

"Mars' seasonal ice has two different origins", says Dr. Paul Hartogh from the MPS. "A part of the carbon dioxide from the atmosphere condensates directly on the surface – similar to the way a layer of frost forms on Earth in cold, clear weather. Another part freezes in the atmosphere", he adds.

The tiny ice crystals accumulate into clouds and fall to the ground as snow.

In the new study, the researchers were now for the first time able to establish a connection between the occurrence of such ice clouds and a wave-like weather phenomenon characterized by a periodic change of pressure, temperature, wind speed, and -direction.

"This weather phenomenon on Mars is unique", says Dr. Alexander Medvedev from the MPS. Indeed, these so-called planetary waves can also be found in Earth's meteorology.

However, not only are the oscillations in pressure and temperature in the lower atmosphere much weaker here. They also occur much less regularly and their wave characteristics are much less pronounced.

"In the Martian northern hemisphere between fall and spring these waves can be found with astonishing reliability", the physicist adds. They propagate eastward with a uniform period of five to six days. Close to the surface, waves with higher frequencies can also be observed.