Despite having drastically different atmospheres, Mars and Earth appear to have similar cloud patterns, suggesting that the features may form in much the same way.
The observations, obtained by the European Space Agency (ESA) Mars-Express spaceships and NASA Mars reconnaissance orbiter, were unexpected. What has perhaps been most surprising to scientists is that the clouds observed above the dry and arid atmosphere of March resembled those found in very different environments on Earth.
“Thinking of a Mars-like atmosphere on Earthyou could easily think of a dry desert or a polar region,” Colin Wilson, Mars Express project scientist, said in a statement (opens in a new tab). “It is therefore quite unexpected that in tracking the chaotic movement of dust storms, parallels can be drawn with processes occurring in the humid, warm and decidedly very different tropical regions of Mars.”
Related: NASA’s Curiosity rover spots strange colorful clouds on Mars
For the research, scientists looked at two dust storms that occurred near the Martian north pole in the spring of 2019. To observe the storms from orbit around the red planet, they viewed footage taken by the surveillance camera Visual Visualization (VMC) from Mars Express and High Resolution Stereo Camera (HRSC) and Mars Color Imager from MRO.
VMC images show the storms growing and then disappearing in a cycle that exhibits common characteristics and shapes as it repeats over periods of several days. Visible in the wider-view HRSC images are spiral shapes between about 1,600 and 3,200 miles (1,000 to 2,000 kilometers) in length. These spirals appear to form similarly to extratropical cyclones observed at mid- and polar latitudes on Earth.
The images also reveal that dust storms on Mars are composed of small, evenly spaced cloud cells that are arranged like pebbles, forming a garden path-like texture that is also seen in the clouds above. above the Earth.
These patterns are created when warm air rises and denser cool air falls in cell-like units – a phenomenon called closed-cell convection. As warm air rises in the center of these cells, cool air falls through “pathways” that form in the gaps between individual cells, the researchers explained.
On Earth, this convection causes clouds to form because the rising warm air contains water, which then condenses and falls as rain. In the dry and arid environment of Mars, however, these rising columns of warm air carry dust. As the air cools and sinks, it carries less dust. As a result, cells are forming on Mars with a familiar granular pattern seen in clouds above Earth, albeit with a dusty rather than watery composition.
The dust cells observed above Mars are useful as a measurement tool, as their movement in sequences of images allows scientists to measure the speed of Martian winds. This process revealed winds blowing up to 87 mph (140 km/h); these high speed winds cause the convection cells to elongate in the direction of the wind.
The lengths of shadows in images taken with VMC, when measured and compared to the known position of the Sunalso revealed the altitude of Martian dust clouds – about 4 to 7 miles (6 to 11 km) – and showed that conventional cells are about 12 to 25 miles (20 to 40 km) wide.
“Despite the unpredictable behavior of dust storms on Mars and the strong gusts of wind that accompany them, we have seen that in their complexity, organized structures such as fronts and cellular convection patterns can emerge,” said Agustín Sánchez. -Levaga, VMC science team leader and lead author of the study, said in the statement.
Earth and Mars are not the only places in the solar system where such cellular convection is seen; ESA Venus Express spacecraft spotted similar patterns in Venusian clouds.
“Our work on Mars dry convection is another example of the value of comparative studies of similar phenomena occurring in planetary atmospheres to better understand the mechanisms underlying them under different conditions and environments,” Sánchez- said. Levaga.
This glimpse of Mars’ clouds gives planetary scientists a better understanding of the dynamics of the Martian atmosphere. Additionally, knowledge of Martian dust storms could help inform future missions to the Red Planet.
Dust storms can block the sunlight that is needed to power the solar cells of robotic rovers exploring the Martian surface. The potentially damaging effects of dust storms on Mars were demonstrated in 2018, when a planetary event blocked sunlight and covered the Opportunity rover’s solar panels with dust, end his mission.
Predicting the evolution of such dust storms could protect solar-powered missions against these powerful natural events and even help future Mars astronauts cope with dust storms.
The team’s research was published Tuesday, November 15 in the journal Icarus.
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