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Krulwich Wonders: Are Those Spidery Black Things on Mars Dangerous? (Maybe)

Wednesday, October 03, 2012 - 11:03 AM


You are 200 miles directly above the Martian surface -- looking down. This image was taken by the Mars Reconnaissance Orbiter on Jan. 27, 2010. (The color was added later.) What do we see? Well, sand, mostly. As you scroll down, there's a ridge crossing through the image, then a plain, then dunes, but keep looking. You will notice, when you get to the dunes, there are little black flecks dotting the ridges, mostly on the sunny side, like sunbathing spiders sitting in rows. Can you see them?

Michael Benson/NASA/JPL/University of Arizona/Kinetikon Pictures

What are those things? They were first seen in 1998; they don't look like anything we have here on Earth. To this day, no one is sure what they are, but we now know this: They come, then they go. Every Martian spring, they appear out of nowhere, showing up -- 70 percent of the time -- where they were the year before. They pop up suddenly, sometimes overnight. When winter comes, they vanish.

As the sun gets hotter, they get more spidery. Here's a closer image -- like the one above, this gorgeous print was created by the photographer Michael Benson, just published in his new book, Planetfall. It shows two mounds of sand. The spidery thingies, you'll notice, stay on the rises, not on the flat sandy plains.

Michael Benson/NASA/JPL/University of Arizona/Kinetikon Pictures

What could they be? Scientists from the U.S. Geological Survey, from Hungary, from the European Space Agency have all proposed explanations; the leading one is so weird, it's transformed my idea of what it's like to be on Mars. For 20 years, I've thought the planet to be magnificently desolate, a dead zone, painted rouge. But imagine this: Every spring, the sun beats down on a southern region of Mars, morning light melts the surface, warms up the ground below, and a thin, underground layer of frozen CO2 turns suddenly into a roaring gas, expands, and carrying rock and ice, rushes up through breaks in the rock, exploding into the Martian air. Geysers shoot up in odd places. It feels random, like being surprise attacked by an monstrous, underground fountain. Here's what it might look like:

Artist rendering by Ron Miller/JPL/Arizona State University

"If you were there," says Phil Christensen of Arizona State University, "you'd be standing on a slab of carbon dioxide ice. All around you, roaring jets of carbon dioxide gas are throwing sand and dust a couple hundred feet into the air." The ground below would be rumbling. You'd feel it in your space boots.

That, anyway, is the leading explanation.The spidery traces that you see in Michael's two prints might be clumps of dark, basaltic sand thrown from the geysers. Or -- say a group of Hungarian scientists -- they might be colonies of photosynthetic Martian microorganisms, warmed from the sun, now sunbathing in plain view. We still don't know for sure. We've been watching those spider-patches come and go for the last decade or so, and for a little while longer, we will have to guess why they're there, or what they're telling us.

We'll have to keep looking.

Michael Benson/NASA/JPL/University of Arizona/Kinetikon Pictures

A 2006 letter in Nature described this idea of geysers near the Martian south pole. Some American scientists then proposed a "Mars Geyser Hopper", an instrument built to investigate geysers that could "hop" from site to site. (Avoiding, one presumes, sudden gushers from below). Michael Benson's new collection of prints, taken from the digital print outs transmitted by exploration space telescopes, are works of science and imagination. The images are black and white in origin; the color is added. Michael calls his technique "true" color, meaning, he's choosing a spectrum that represents what a human eye would see if a human eye (and brain) were on the scene. His newest is called "Planetfall: New Solar System Visions."


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Comments [10]

Evyl Robot Michael from Fly Over Country

@ Andres - It obviously comes from those gas-guzzling rovers that we put on the surface. In all seriousness, the majority of atmospheric CO2 is volcanic in origin, despite the political spin of those who claim that it's all teh hoomanz fault. I would imagine that on other planets, a similar phenomenon would be to blame. Nah. It's probably our rovers.

Dec. 03 2012 05:37 PM

For those who have not forgotten the "Fact of the Matter" this again gets at the heart of the issue of Yellow Rain, and what was wrong with the podcast from a third party perspective.

Radiolab has so much to answer for.

Nov. 13 2012 07:39 PM

For those who have not forgotten the "Fact of the Matter" this again gets at the heart of the issue of Yellow Rain, and what was wrong with the podcast from a third party perspective.

Radiolab has so much to answer for.

Nov. 13 2012 07:38 PM

Just found this: Kao Kalia Yang's (interpreter for the Yellow Rain piece) first response to "Yellow Rain"

Oct. 23 2012 11:29 AM
Larry from Ohio

Ziggy Stardust and the Spiders from Mars....

Oct. 21 2012 12:24 PM
Shane from Michigan

what are the black lines that appear out side of shadows? They appear on dunes and cliffs and appear to be the same color as the spiders.

there are so many of these spiders I see no shadows from active volcanos, why?

What are the surface wind conditions? The dunes do not appear to match volcanic spray patterns.

What are surface temperatures? What are surface temperatures in the shade? could they support any known living organisms?

can you tell substance weight by where it is deposited on the dunes relative to where the sand deposits? Similar to gold being heavier than sand in a river.

Oct. 17 2012 10:41 AM

Are you sure we don't have these on earth? The Eureka Dunes in Death Valley have similar, although slightly different, black splotches on them. You can see them on google earth. I believe on the Eureka Dunes it is black garnet sand that sifts to the surface. Maybe something similar could happen seasonally on Mars if the wind patterns change?

Oct. 13 2012 04:56 PM
William from Nevada City, CA

Thank you for this, Mr. Krulwich. You're doing wonders for science and humanity!
The more you put your finger on planetary sciences, especially mars, the better. It is humanity's current and greatest frontier.

Oct. 08 2012 12:27 AM

Very cool stuff down there in the Planum Australe. Thank you for sharing these spectacular photographs, Robert. Here's hoping that NASA funds the proposed mission down there to check this phenomenon out, and if not NASA, then the ESA or a private entity. It would be incredible to have a rover or other craft on the surface study that environment and capture video of one of the geysers going off.

@Andres, Carbon dioxide exists in a number of places in the solar system that are devoid of life. The atmosphere of Venus consists nearly entirely of carbon dioxide, and Mars' thin atmosphere is comprised nearly entirely of carbon dioxide as well. The Hungarian team's idea about micro-organisms is interesting, but Mars' lack of a substantive magnetic field to shield its surface from solar radiation makes that explanation unlikely.

Oct. 05 2012 11:38 PM

I guess my question would be where does the carbon dioxide come from? Cellular respiration from bacteria or other single celled organisms?

Oct. 05 2012 07:28 PM

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