The Arsia Mons Elongated Cloud (AMEC) forms, stretches and fades within a single Martian day, growing up to 1,800 km (1,118 miles) long before evaporating. The cycle repeats every morning for several months.
ESA’s Mars Express orbiter first imaged the cloud in 2018 and has been watching it ever since.
Planetary researchers had long identified it as an orographic cloud, a type also seen on Earth, which forms when wind flows over mountains or volcanoes.
But computer simulations built on that assumption could never reproduce what Mars Express actually saw.
“To create the AMEC in our modelling, we found that we needed to include some exotic physics… physics that, while included in textbooks, is treated as theoretical and usually thought not to happen in nature,” said lead author Dr. Jorge Hernández-Bernal, a researcher at Sorbonne Université and CNRS.
“It certainly hasn’t been seen in action before.”
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