Researchers can't sample Martian clouds, but they were able to create Mars-like conditions on Earth. Using the world’s largest cloud chamber, researchers from the Massachusetts Institute of Technology created clouds and discovered there needs to be more humidity for cloud formation on Mars than what is required on Earth.
MIT researchers said that many models of cloud formation on Mars use humidity levels similar to those on Earth. While scientists can't obtain a cloud sample from Mars, they conducted experiments at the Aerosol Interaction and Dynamics in the Atmosphere facility in Germany. They recreated Mars-like conditions by pumping out oxygen and creating an atmosphere of carbon dioxide and nitrogen while reducing the temperatures to minus-120 degrees Fahrenheit. The study was published in the Journal of Geophysical Research: Planets.
The biggest problem with current Mars cloud formation models is the assumption of using Earth-like conditions. On Earth, clouds form at 100 percent humidity but that may not be the case on Mars. The researchers said, "Many Martian atmospheric models struggle to correctly predict clouds and, with insufficient data, some use untested simplifications that cloud formation occurs exactly at the saturation point of the condensed phase or at the same conditions as terrestrial cirrus clouds.”
Using the AIDA facility, the researchers discovered clouds form on Mars after setting the humidity inside the cloud chamber to a humidity of 190 percent, significantly higher than what is needed on Earth. “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," MIT's Dan Cziczo says of current models. "But we found you need more to kick-start the process.”
The researchers seeded clouds with mineral dust, meant to simulate a dust storm on Mars. Water vapor can cling to these tiny particles paving the way for cloud formation. To track cloud formation, researchers pointed a laser through the chamber and observed any dispersion. Through the course of the experiment, the researchers were able to create 10 Martian clouds, each forming over 15 minutes, and discovered the extremely high humidity necessary to create these clouds.
Cziczo plans to conduct more research at the AIDA facility to learn why cloud formation on Mars needs such high humidity as well as how water is transported across the planet. The cloud chamber will be upgraded to reach even lower temperatures, allowing for a better representation of the conditions on Mars.
“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," he said.
The research could also lead to improvements in current atmospheric models of Mars.