Signs that Ancient Rivers Flowed Across the Surface of Mars, Billions of Years Ago

A topographic image of an area of anceint riverbeds on Mars. Created with data from the High-Resolution Stereo Camera on the Mars Express Orbiter. Image Credit: ESA/DLR/FU Berlin http://www.esa.int/spaceinimages/ESA_Multimedia/Copyright_Notice_Images

Billions of years ago, Mars was likely a much warmer and wetter place than the cold, dry, barren world we see today. Whether there was life there or not remains an open question. But there’s a massive, growing wall of evidence showing that Mars may have had the necessary conditions for life in the past, including at least one system of river valley networks.

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There’s a Funny Cloud on Mars, Perched Right at the Arsia Mons Volcano. Don’t Get Too Excited, Though, it’s not an Eruption

A funny cloud on Mars. The ESA' Mars Express orbiter captured this image of an elongated cloud forming near the Arsia Mons volcano at the Martian equator. Image: ESA/Mars Express

The ESA’s Mars Express orbiter has spotted a funny cloud on Mars, right near the Arsia Mons Volcano. At first glance it looks like a plume coming out of the volcano. But it’s formation is not related to any internal activity in this long-dead volcano. It’s a cloud of water ice known as an orographic or lee cloud.

The cloud isn’t linked to any volcanic activity, but its formation is associated with the form and altitude of Arsia Mons. Arsia Mons is a dormant volcano, with scientists putting its last eruptive activity at 10 mya. This isn’t the first time this type of cloud has been seen hovering around Arsia Mons.

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