Martian Clouds are Formed in More Humid Conditions Than Clouds on Earth

Researchers conducted a cloud chamber experiment where researchers concluded that clouds on Mars were formed in more humid conditions compared to clouds on Earth.

Scientists have earlier stated that unlike the clouds on Earth that are found around the entire planet, clouds on Mars are plentiful only in the equatorial region. It is not possible to spot dense clouds like those on Earth in a Martian atmosphere, but they do form on the Red Planet and are basically of two types, namely the 'water ice clouds' and the 'high altitude dry ice clouds .'

Images of the Martian sky provided by NASA's Opportunity rover revealed thin, high altitude wispy strands similar to cirrus clouds. Based on the atmospheric conditions of the Red Planet, scientists suggest that the Martian clouds mainly consist of carbon dioxide and water based ice crystals. It is challenging for the scientists to know the precise conditions that trigger the formation of such cloud, without having samples directly from the Martian cloud.

In order to solve this, a team of researchers at the Massachusetts Institute of Technology, recreated Mars like conditions in a three story cloud chamber in Germany. In this cloud chamber they adjusted the temperature and humidity in order to match the Martian conditions.

The researchers were able to successfully form clouds at extremely low temperatures like the one found on the Red Planet.  But soon they noticed that to form clouds in such temperatures, they had to change the chamber's humidity to 190 percent i.e. more than what the cloud formation on Earth requires. The researchers suggest that their finding will improve the conventional models of Martian atmosphere as most of these models presume that clouds on Mars require humidity levels like similar to Earth. This new finding will also help scientists to study the mechanism of how the Red Planet transports water through the atmosphere.

"A lot of atmospheric models for Mars are very simple," Dan Cziczo, the Victor P. Starr Associate Professor of Atmospheric Chemistry at MIT, said in a statement."They have to make gross assumptions about how clouds form: As soon as it hits 100 percent humidity, boom, you get a cloud to form. But we found you need more to kick-start the process."

The facility in which the experiment was conducted was first a nuclear reactor that was later converted into a cloud chamber. The facility was first designed to study the Earth's atmospheric conditions.

They scientists first removed the oxygen and refilled the chamber with the common Martian component, carbon dioxide. A dust storm was created by pumping fine particles similar in size and composition to the mineral dust found on the Red Planet. These particles act like cloud seeds around which water vapour can adhere to form cloud particles.

They finally set the temperature by first adjusting it to the coldest temperature at which clouds on Earth are formed, they then stopped at the chamber's lowest setting. They formed 10 such clouds over a week and with the help of lasers they detected the cloud formation. On analyzing the data over the next six months they learnt that the Martian clouds are formed at the lowest temperature and for this they required extremely high humidity for the water vapour to form ice crystals around the dust particles. 

But what continues to stay as a mystery is, why the Martian clouds required such humid conditions to form.

Cziczo concluded, "If we want to understand where water goes and how it's transported through the atmosphere on Mars, we have to understand cloud formation for that planet. Hopefully this will move us toward the right direction."

The study was documented in the Journal of Geophysical Research Planet.