New Mexico Rock Helps to Explore Mars

SOCORRO, N.M. September 4, 2012 – Thanks to the Bureau of Geology, a division of New Mexico Tech, a piece of the Land of Enchantment is on Mars. The Curiosity rover is carrying a small disc of basalt, sampled from rocks found in Box Canyon, near Socorro. The basalt disc will help ensure the accuracy of the analyses the rover makes of materials it encounters on its journey up the slopes of Mount Sharp.

 Chamberlin in-the-fieldwithharrisonandcikoski

 Dr. Richard Chamberlin (right) working in the field with Bureau of Geology scientist Colin Cikoski and Tech geology professor Dr. Bruce Harrison.


“I think this is very exciting,” said Greer Price, Director of the New Mexico Bureau of Geology and Mineral Resources. “To me, this points out that the work we do in New Mexico has implications far beyond the state. This is a neat story.”

Dr. Richard Chamberlin, who recently retired from the Bureau, collected specimens of volcanic rock to be used as a calibration target for the Alpha Particle X-ray Spectrometer instrument, or AXPS, that is aboard Curiosity, also known as the Mars Science Laboratory. That spectrometer is one of 10 state-of-the-art analytical instruments on the roving Mars Science Laboratory.

Dr. Penny King of the Institute of Meteoritics at the University of New Mexico first contacted Chamberlin in 2007. King was helping NASA search for a basaltic rock that might be useful as a reference standard for the Mars mission. Chamberlin recognized the NASA scientists requirements would be met by a rare type of volcanic rock that is unusually uniform in composition, in addition to being dense and fine grained like many volcanic rocks.

Chamberlin suggested the 8.5 million-year-old “basalt of Broken Tank” as a possible candidate, because it is a very fine grained lava devoid of any crystals visible to the naked eye—a texture that geologists call aphyric. Of many ancient basalt flows in the Socorro region, only the basalt of Broken Tank is aphyric. In November of 2007, Chamberlin and King collected a large “test” sample of the basalt of Broken Tank (BT-2) near Box Canyon, which also happens to be a popular rock climbing site west of Socorro. About 200 other samples were considered for use by the Mars mission.

“As basalt magma ascends from great depth in the earth’s mantle it tends to cool and partially crystallize before it erupts at the surface. So most lava flows contain a few percent of small crystals suspended in the liquid at the time of eruption; this makes them non-uniform in composition.” Chamberlin said. “They were looking for an unusual variation of basalt — one that was erupted as 100 percent liquid. That’s pretty rare in geological processes because it requires basaltic magma in the mantle (at about 60 miles depth) to be transferred rapidly to the surface with minimal cooling. Magma under high pressure can fracture overlying colder rocks and then drive the fracture tip toward the surface, allowing the magma to flow upwards behind it. This process, called dike injection, can transport magma from the mantle to the surface in a few days.”

chamberlin-BasaltBrokenTank BoxCanyon

The road to Box Canyon west of Socorro. The red dot signifies the location where Richard Chamberlin found 'aphyritic' basalt that is now on Mars.


Fortunately, from previous work making geologic maps in the Socorro region, Chamberlin knew where to find exposures of the basalt of Broken Tank. A geologic map of the Luis Lopez quadrangle, which shows the basalt outcrops, was put online in 2002. Chamberlin also published related findings about the basalt of Broken Tank in New Mexico Geology in 2011.

“The source volcano isn’t known. It is probably buried under younger sediments in the valley near San Antonio,” he said. “Geologic map patterns and precise age determinations indicate the lava flowed westward from the San Antonio area to Table Mountain and then north to the Box Canyon area. We also mapped the character of the sediments under the lava flow, which allows us to estimate the downstream (down slope) direction just prior to the eruption. It’s detective work, using rock layers as clues– that’s what geology is. We look for patterns and clues and solve the mysteries of Earth history”

And that particular mystery uncovered samples that will soon help NASA unravel new mysteries on Mars. The BT-2 basalt sample will be used to provide a baseline for samples analyzed on the Martian surface.

Chamberlin – like many Techies – has been paying attention to the progress of the Mars mission both during and since the landing. He said the recently returned images of Mount Sharp give the distinct impression of layered rocks.

“It certainly looks like sediments, so they have a lot to learn,” he said. “Curiosity is a $2.5 billion scientific endeavor and I guess I helped a little bit. And my work didn’t cost them anything either. The State of New Mexico paid for my time. I was glad to help.”

The Broken Tank sample was selected because of its toughness, very small interlocking crystals, homogeneity, and lack of vesicles (gas bubbles that often occur in volcanic rocks). The calibration standard needed to be elastic and tough—resistant to fracture — because of the intense vibrations and stresses placed on it during its journey to Mars. A rock with very small evenly distributed crystals and no holes in it is useful for a standard because repeated calibration analyses of such a sample should predictable results. Thanks to NASA, the BT-2 sample is now probably the most intensely analyzed basalt from New Mexico.

The AXPS uses X-rays to determine elemental chemistry of rocks or other geologic materials. The instrument is one of several sophisticated analytical tools aboard Curiosity. Repeated measurements of a known standard will ensure that results from the AXPS continue to be reliable, especially in the situation that unexpected results are encountered. The calibration target (BT-2) was cut into a disk that is 4.2-centimeters in diameter and 3-millimeters thick. The New Mexico rock is one of several calibration targets, including a 1909 penny, that will be used by Curiosity’s many instruments.




 – NMT –

By Thomas Guengerich/New Mexico Tech

and Adam Read/Bureau of Geology