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Spiders galore on Mars!

Spiders galore on Mars
Click for full image.

Cool image time! The photo to the right, cropped to post here, was taken on February 27, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows a nice collection of what scientists have informally (but permanently) labeled as spiders, strange formations that exists only in the regions of the Martian south pole.

The spiders are believed to have formed because of the coming and going of the dry ice mantle in the polar regions that falls as snow in the winter and then sublimates away come the spring. Because dry ice is mostly clear, the spring sunlight penetrates it and warms the underlying surface, which acts to warm the base of the dry ice mantle. CO2 gas builds up, trapped below the dry ice, until the pressure causes it to break the dry ice at a weak point and spew outward, carrying with it dust that blackens the surface above. You can see three examples in today’s image.

Spiders however only happen at the south pole. In the north much of the terrain is formed by unstable dunes, which change from year to year, thus causing the gas breakage to occur at random and different spots.

In the south however the terrain is more stable, a surface of ice and dirt. The spiders form because the trapped gas always follows the same path from year to year to the same weak points, carving riverlike tributaries until these feeders combine and build up enough gas pressure to crack the overlying dry ice so that the gas can escape.

Though the gas functions much like a river of water, it has one fundamental difference that makes this phenomenon wholly Martian and quite alien. On Earth rivers flow downhill. On Mars, the gas in these spider tributaries is flowing upward, seeking a path into the atmosphere above.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News


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