No Martian Trees

Arthur C. Clarke, the famous writer, claimed in 2001 that a photograph taken by the Mars Global Surveyor spacecraft showed vegetation on Mars. The objects are shaped like banyan trees, and appear during the planet’s spring, he observed; his certainty that the photo showed life was in the “high 90s.”

I was excited about that because the large, spreading patches did look like vegetation.

[View taken by Mars Orbital Surveyor shows strange tree-like patterns at Mars’ south pole.]

But in 2007 Clarke’s notion was disproved. Now, detailed photos released a few days ago serve to underline that these objects are not living, but also to show just how delightfully alien Mars is.

The color photographs were taken by the High Resolution Imaging Science Experiment aboard the Mars Reconnaissance Orbiter, which began circling the planet three years ago. HiRISE, managed by the University of Arizona, Tucson, is such a powerful camera that it could spot an astronaut on the surface.

[New photo by HiRISE camera on Mars Reconnaissance Orbiter.]

A University of Arizona news release dated March 25 notes that HiRISE “is seeing signs of spring on Mars.” Taken above the south polar region, the photos show evidence of seasonal change in the polar cap, which is a deposit of frozen carbon dioxide, or dry ice.

The dry ice deposit laid down in the winter may be as much as a meter (39 inches) thick, according to the release, quoting HiRISE deputy principal investigator Candice J. Hansen-Koharcheck, who works at the Jet Propulsion Laboratory, Pasadena, Calif. As warmer weather thaws the dry ice in the spring, the solid carbon dioxide sublimates into the low-pressure atmosphere.

Hansen-Koharcheck was quoted as saying the seasonal ice cap thins from the bottom and gas pressure builds up under the cap. Eventually gaseous carbon dioxide will spout from a weak spot or a crack, “often carrying a little dust from the surface below.”

Swirled by Martian wind, the erupting dust leaves a strange, beautiful pattern on the remaining ice.

Clarke was the author of many science and science-fiction books, including “2001: A Space Odyssey,” a film and book he wrote with the movie director Stanley Kubrick. He is considered the father of the communications satellite and the weather satellite. He died at Sri Lanka, his adopted home, on March 19, 2008, age 90.

While he was wrong about banyan-tree-like vegetation on Mars, doubtless the grand old writer would have been delighted with strange patterns produced by unearthly processes on a neighboring world.

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A personal note: For the past 10 weeks I have written blogs to be posted on Mondays, Wednesdays and Fridays. My blogs tend to be more essay than news item, which takes some work. The task is enjoyable but done too often it extracts a toll on an old retired fellow with diabetes. This is especially true because I want to also write a book of astronomical essays, many based on my blogs. Consequently, I’m slacking off. For now I will do blogs for the Tuesday and Thursday editions. If I feel peppier later I may resume the thrice-weekly schedule. — Joe

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