Despite having radically 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’s (ESA) Mars Express spacecraft and NASAs Mars Exploration Orbiter, were unexpected. Perhaps most surprising to scientists, the clouds were observed above the dry and arid atmosphere of Mars resembled those found in very different environments on Earth.
“When thinking of a Mars-like atmosphere on Soil“You could easily think of a dry desert or arctic region,” Mars Express project scientist Colin Wilson said in a pronunciation (opens in new tab). “It is therefore quite unexpected that by tracking the chaotic movement of dust storms, parallels can be drawn with the processes taking place in Earth’s humid, hot, and decidedly very un-Mars-like tropical regions.”
Related: NASA’s Curiosity rover sees strange, colorful clouds on Mars
For the study, the scientists looked at two dust storms that occurred near the north pole of Mars in the spring of 2019. To observe the storms from orbit around the Red Planet, they viewed images captured by NASA’s Visual Monitoring Camera (VMC). Mars Express and High-Resolution Stereo Camera (HRSC) and MRO’s Mars Color Imager.
The VMC images show the storms growing and then disappearing in a cycle that shows common features and shapes as it repeats over periods of days. Visible in the wider 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 seen at mid-latitudes and polar latitudes on Earth.
The images also show that dust storms on Mars are made up of regularly spaced, smaller cloud cells arranged like pebbles, forming a garden path-like texture that can also be seen in clouds above Earth.
These patterns are created when hot air rises and denser, cool air falls into cell-like units — a phenomenon called closed-cell convection. As hot air rises through the center of these cells, cool air falls through “pathways” that form in gaps between the individual cells, the researchers explained.
On Earth, this convection causes clouds to form because rising hot air contains water, which then condenses and falls as rain. However, in the dry and arid environment of Mars, these rising columns of hot air carry dust. As the air cools and settles, it carries less dust with it. As a result, cells form over Mars with a familiar grain pattern seen in the clouds above Earth, albeit with a dusty rather than watery composition.
The dust cells seen above Mars are useful as a measurement tool, because their motion in sequences of images allows scientists to measure Martian wind speeds. This process has revealed winds blowing up to 87 mph (140 kph); these fast winds cause the convection cells to elongate in the direction the wind is blowing.
The lengths of the shadows in images created with VMC measured and compared to the known position of the Sunalso revealed the height of the Martian dust clouds — about 4 to 7 miles (6 to 11 km) — and showed that the convention cells are about 12 to 25 miles (20 to 40 km) wide.
“Despite the unpredictable behavior of Martian dust storms and the strong gusts of wind that accompany them, we have seen that organized structures such as fronts and cellular convection patterns can emerge within their complexity,” 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 world solar system where such cellular convection is seen; ESAs Venus Express spacecraft saw 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 underlying mechanisms under different conditions and environments,” Sánchez-Levaga said.
This insight into Mars’ clouds gives planetary scientists a better understanding of the dynamics of the Martian atmosphere. In addition, knowledge of dust storms on Mars could help inform future missions to the Red Planet.
Dust storms can block the sun’s light needed to power the solar cells of robotic rovers exploring the surface of Mars. The potentially damaging effects of dust storms on Mars were demonstrated in 2018, when a planet-wide event blocked sunlight and covered the Opportunity rover’s solar panels with dust. finishing his mission.
Predicting the evolution of such dust storms could protect solar-powered missions from these powerful natural events and even help future Mars astronauts deal with dust storms.
The team’s research was published Tuesday (Nov. 15) in the journal Icarus.
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