According to a news release from the Massachusetts Institute of Technology, cloud-chamber experiments reveal that clouds on the Red Planet develop in much more humid conditions than clouds on Earth.

Without taking a more in-depth look at Mars’ clouds, one might think they are a lot like our cirrus clouds. Based on what scientists already know about Mars’ atmosphere, these clouds are probably composed of either carbon dioxide or water-based crystals. It’s hard to determine the exact conditions that resulted in such clouds without examining a Martian cloud directly.

In theory, Mars and Earth can never come closer to each other than 33.9 million miles so researchers at MIT settled for the next-best approach: they’ve developed Red Planet-like conditions within a three-story tall cloud chamber, altering the chamber’s temperature and relative humidity to equal the conditions on Mars — essentially developing Mars’ clouds on Earth.

While the researchers were able to make clouds at the extremely cold temperatures usually observed on the Red Planet, they found that cloud development in such conditions demanded altering the chamber’s relative humidity to 190 percent — much greater than cloud development necessitates on Earth. The result should enhance conventional models of the Red Planet atmosphere, many of which act as if Mars’ clouds need humidity levels similar to those detected on Earth.

“A lot of atmospheric models for Mars are very simple,” notes Dan Cziczo, the Victor P. Starr Associate Professor of Atmospheric Chemistry at MIT, 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.”

According to Cziczo, the finding will also better scientists’ comprehension of how the planet moves water through the atmosphere.

The researchers performed their experiments at the Aerosol Interaction and Dynamics in the Atmosphere facility in Karlsruhe, Germany (it happens to be the world’s biggest cloud chamber).

Although the facility was originally constructed to examine atmospheric conditions on Earth, the researchers recognized that the chamber could be altered to simulate conditions on the Red Planet. To alter the facility for their experiments, the researchers first pumped all the oxygen out of the chamber, and instead added inert nitrogen or carbon dioxide — components commonly found in Mars’ atmosphere.

They then made a dust storm, pumping in fine particles similar in size and composition to the mineral dust located on the Red Planet. These particles behave as cloud seeds around which water vapor can join to develop cloud particles.

After “seeding” the cloud chamber, the researchers altered the temperature, first changing it to the coldest temperatures at which clouds develop on Earth. During the experiment, they slowly lowered the temperature, eventually halting at the chamber’s lowest setting (-120 F).

By altering the chamber’s relative humidity under each temperature setting, the researchers were able to make clouds under warmer, Earth-like temperatures, at expected relative humidities.

Over the course of a week, the researchers made 10 clouds, with each cloud forming in approximately 15 minutes. The researchers utilized a system of lasers to detect cloud formation. Any clouds that develop scatter laser light, which is then detected and documented by computers. Scientists observing from outside the cloud chamber can obtain the size, number, and composition of cloud particles from the computer.

By examining this data for the next six months, the researchers discovered that clouds that formed at the lowest temperatures needed very high relative humidity in order for water vapor to develop an ice crystal around a dust particle. According to Cziczo, researchers aren’t sure why Mars’ clouds require such humid conditions to form, but they want to conduct additional experiments to find an answer to that question.

By next fall, the cloud chamber will be able to conduct cloud experiments at even lower temperatures.

“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,” Cziczo posits. “Hopefully this will move us toward the right direction.”

The study’s results are described in greater detail in the Journal of Geophysical Research: Planets.