History of Mars unveiled?
Washington: In a rough-and-tumble wonderland of plunging canyons and towering buttes, some of the still-raw bluffs are studded with elevated, six-sided stone columns so orderly and trim that they could almost pass as relics of a gigantic temple.
The secret of how these columns, packed in edge to edge, formed en masse from a sea of molten rock is encrypted in details as tiny as the cracks running across their faces.
To add to this mystery’s allure, decoding it might do more than reveal the life story of some local lava: it might help describe the history of Mars.
But with trips to Mars hard to come by, the interns of the 2011 Lunar and Planetary Sciences Academy (LPSA) at NASA’s Goddard Space Flight Center in Greenbelt, Md., travelled to the Channeled Scablands of eastern Washington state.
It’s a region that has been helping scientists understand the forces that shape planetary surfaces for a century “The Legacy of Megafloods”.
Here, the honeycomb-shaped columns bear a striking resemblance to those spotted in images of Marte Vallis and other regions of Mars.
“Many of the landscape features in the Channeled Scablands are similar to ones seen on the surface of Mars, so we can study volcanic activity on Mars by looking in our own backyard,” said Andrew Ryan, who was the student coordinator for the LPSA field trip and is now in graduate school at Arizona State University in Tempe.
A key step was to find out “what we could learn about the columns in the Channeled Scablands from the air,” said Cynthia Cheung, principal investigator for Goddard’s Lunar and Planetary Sciences Academy.
That’s because the images of the Mars columns had been taken by the HiRISE (for High Resolution Imaging Science Experiment) camera on NASA’s Mars Reconnaissance Orbiter.
The aerial measurements could then be compared to measurements taken on the ground.
“It was cool to see the similarities between Earth and the Red Planet,” said Melissa Guzman, an LPSA intern.
“And because of the hands-on nature of our field trip, I could imagine myself on Mars years from now, making similar measurements.”
The interns’ immediate focus, though, was on the orderly columns, especially what the ones in Washington State could tell them about Mars.
In the Channeled Scablands, the molten basalt that formed the columns seeped up through gashes in the ground and spread far and wide. More than a hundred of these lava flows smothered the land during a series of eruptions spanning some 10 million years, building up a rock layer that reached a thickness of two miles, the average depth of the Atlantic Ocean.
The columns took shape when the lava cooled and hardened. As the heat escaped, the basalt contracted from all sides, opening a network of cracks that divided the once-seamless surface into a forest of six-sided pillars. (Depending on the conditions when the lava cooled, the columns can have from four to seven sides.)
These are called jointed basalt columns, and they can be found on every continent except Antarctica, with Giant’s Causeway in Ireland and Devils Postpile in California as two of the most famous examples.
It’s possible to figure out how quickly the basalt cooled, and thus how quickly the columns formed, by measuring the distance from one small horizontal crack, called a stria, to the next.
But details such as striae are too small to be seen in the images of the Martian columns. That means the stria height must be deduced from a feature that can be resolved: the column width.
To figure out how these two features are related, the LPSA interns measured both characteristics at three locations in the scablands.
One additional step was needed to complete the Mars simulation: The students had to take images of the basalt columns from above, just as the HiRISE camera had done when orbiting Mars.
For this, the team brought along a remote-controlled (RC) plane and a six-bladed miniature helicopter, called a hexacopter. Licensed RC pilots flew the aircraft, with interns Neil Taylor and Josh Mann working on the imagers that flew on the aircraft. Weiss and Brian Jackson, one of the LPSA trip leaders and Weiss’s mentor at Goddard during the internship, guided the flight paths.
“The initial plan was to tilt the RC plane so that it was almost on its side and to fly it along the side of the cliff,” explained Jackson.
“But that didn’t work as well as we expected. So instead, we flew the hexacopter up and down the cliff face. That gave us the kind of images we needed,” Jackson added.
Later, Weiss estimated the widths of the basalt columns based on the aerial images. With that information in hand, he was ready to estimate the striae heights for the Mars columns and then plug that value into the equation for the cooling rate. (ANI)
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