Researchers Model the Mysterious 1,000-Mile Cloud on Mars

Scientists have recently modeled the formation of a recurring, 1,000-mile-long cloud near the Arsia Mons volcano on Mars, according to a study published in Nature Geoscience. First recorded by a probe in 2018 and known as the Arsia Mons Elongated Cloud (AMEC), this wispy formation emerges every morning during the Martian spring and summer, grows up to 1,000 miles long, and then disappears before the cycle repeats.

Before recent modeling efforts, researchers lacked a plausible explanation for the AMEC phenomenon. According to lead study author Jorge Hernández-Bernal, a planetary scientist at Sorbonne Université in Paris, researchers found they had to include theoretical physical processes not previously observed in nature to successfully simulate the cloud in computer models.

How the Martian Cloud Forms

Unlike typical cloud formation on Earth, which relies on water vapor condensing around tiny particles like dust or salt, the study suggests the AMEC forms through a process called homogeneous nucleation. In this process, vapor converts directly into ice crystals without the aid of debris.

• Required Conditions: The process demands extreme environmental factors, including a sharp temperature drop of 30 degrees Celsius within 10 minutes and extremely high relative humidity.
• Role of Arsia Mons: Wind currents striking the 65,000-foot-tall volcano generate a powerful atmospheric wave, launching moist air high into the atmosphere within minutes.

Broader Implications and Verification

While scientists previously theorized that homogeneous nucleation could occur in the upper atmospheres of planets like Venus or Earth, it has never been directly observed due to the extreme humidity levels required—levels exceeding any measured values on Earth by more than 100,000 times.

Researchers note that such high humidity levels were previously unknown on Mars as well. Because atmospheric data for Mars is more limited than for Earth, successfully reproducing the cloud in simulations is considered a notable development by the study authors. Readers interested in verifying the original research can consult the published paper in Nature Geoscience or review institutional press releases from Sorbonne Université.