The ESA’s Mars Categorical has revealed that Mars produces surprisingly Earth-like cloud patterns that are similar to those found in our planet’s tropical regions.
The atmospheres of Earth and Mars are vastly different. Mars’ dry, cold environment is almost entirely composed of carbon dioxide, whereas Earth’s is rich in nitrogen and oxygen. Its atmospheric density is less than one-fiftieth of that of Earth, or about 35 kilometres above the planet’s surface.
Despite being vastly different, their cloud patterns have been discovered to be remarkably Earth-like, pointing to related formation processes.
Spiral storm near the North Pole of Mars
A new study delves deeper into two mudstorms that occurred near Mars’ North Pole in 2019. The storms had been tracked throughout the spring on the North Pole. The native storms typically rage across the receding ice cap.
The storms were imaged from orbit by two cameras on Mars Categorical – the Visible Monitoring Digital camera (VMC) and the Excessive Decision Stereo Digital camera (HRSC), as well as the MARCI digicam on NASA’s Mars Reconnaissance Orbiter.
The VMC photographs show that the storms appear to develop and disappear in repeated cycles over a period of days. It exhibit common features and shapes. Spiral shapes can be seen in the larger views of the HRSC photographs. The spirals range in size from 1000 to 2000 km. And their origin is similar to that of extratropical cyclones seen in Earth’s mid-latitudes and polar latitudes.
Cloud formations on Mars and Earth
The images show a unique phenomenon on Mars. They claim that the martian mud storms are made up of closely spaced smaller cloud cells that are organised like grains or pebbles. Clouds in Earth’s environment exhibit this sensation.
Convection creates the familiar textures, in which hot air rises because it is less dense than the cooler air around it. The type of convection seen here is known as closed-cell convection. It occurs when air rises within the centre of small cloud pockets, or cells. The gaps in the clouds are pathways for cooler air to sink beneath the new rising air.
On Earth, rising air contains water, which condenses to form clouds. The mud clouds imaged by Mars Categorical follow the same path. But on Mars, the rising air columns are made up of mud rather than water. The Sun heats dust-laden air, causing it to rise and form dusty cells.
Wind velocity can be calculated by tracking the movement of cells in a series of photographs. Wind speeds of up to 140 km/h blow over the cloud options. It caused the shape of the cells to elongate within the path of the wind. Nature creates these orderly patterns despite the chaotic and dynamic atmospheres of Mars and Earth.
“When considering a Mars-like environment on Earth, one might think of a dry desert or polar region.” It’s not surprising that by tracking the chaotic motion of mud storms, parallels can be drawn with processes that occur in Earth’s moist, hot. And decidedly un-Mars-like tropical areas,” says Colin Wilson, ESA’s Mars Categorical challenge scientist.
The measurement of the altitude of mud clouds is one key perception made possible by the VMC photographs. The size of the shadows they cast are measured and combined with information about the location of the Sun to calculate the peak of the clouds above the Martian surface. The results showed that mud can reach 6-11 km above the bottom and that cells have typical horizontal sizes of 20-40 km.
Monitoring the evolution of mud storms is critical for protecting future solar-powered missions. And eventually crewed missions to the planet – from such powerful phenomena.