Imagine getting to the bottom — literally — of a mystery buried for thousands of years by taking an X-ray of the ground.

What Lies Beneath
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Thanks to the revival of a 30-year-old technique, a team of physicists and archaeologists is doing something like that to learn about hidden Mayan temples. But rather than using X-rays, they’re exploiting tiny, Earth-penetrating particles created by cosmic rays that stream in from space.

Physicist Roy Schwitters and his colleagues at the University of Texas, Austin, hope to find chambers hidden in underground temples built by the Mayans at a site dating to A.D. 250-900 in Belize. Many of the mounds there remain largely unstudied for fear of disturbing their fragile walls or the relics inside.

The hope is to target future excavations directly to the chambers, where the researchers would be more likely to find the sophisticated vestiges of Mayan life. The vibrant pre-Columbian culture remains veiled in mystery.

"There is good reason to believe [the structures] contain rooms and chambers … that have been likely undisturbed since the time of the Maya," Schwitters said during a talk at the annual meeting of the Council for the Advancement of Science Writing last week.

Their technique relies on tiny, high-energy particles that rain harmlessly on Earth as a byproduct of constant cosmic rays streaming from the sun and other sources. Those particles, called muons, penetrate the ground and begin to decay, reaching depths of hundreds of feet before dissipating entirely.

Since their energy frequencies change depending on the density of the material they have recently encountered, muons tell a story about what’s in the upper layers of the ground.

Schwitters’ idea is to place half a dozen muon detectors around a structure, let them collect data for a few weeks, and then analyze that data to find the chambers.

"It literally is like tomography in the medical sense," Schwitters explained. "You can image big things — like 100-meter-sized things — with a couple of months’ worth of data."

His proof of concept came 30 years ago, when the technique was conceived and developed by physicist and Nobel laureate Luis Alvarez to study the Second Pyramid of Chephren in Egypt. Alvarez conducted one experiment with his detector, and though he found no unknown chambers, he considered the experiment a success.

The technique never caught on, Schwitters told Discovery News, because "the high-energy physics community was totally engaged in a very exciting period of discovery which took off about the time of the Alvarez experiment with the advent and subsequent confirmation of the standard model of particle physics."

What’s more, detectors at the time were large, unwieldy and expensive to build.

Muon Tomography
Roy Schwitters

"The detectors are more robust and somewhat less expensive today, and no other technology has proven to be superior for imaging such large structures," Schwitters said.

He and a team of graduate students have built and are testing a prototype detector, which weighs about 200 pounds (lightweight compared to the original, which weighed almost a ton). They hope to begin field work in Belize by the spring of 2009.

There are other ways to study buried structures without disturbing them, such as ground-penetrating radar. But muon tomography has an advantage because muons penetrate so deeply into the ground — on average, a few miles rather than a few hundred feet, as is the case with radar.

"It’s not practical to consider when we’re talking about going in 50 meters," said Schwitters.

Still, the technique hasn’t caught on widely.

"To my knowledge, no one is using [muon tomography] in mainstream archaeology," said Kenneth Kvamme, an anthropologist at the University of Arkansas and editor of the journal Archaeological Prospection, which specializes in underground studies.

In the future, that could change, said Schwitters.

"This technology, even though it sounds futuristic, could hold promise as an energy source for looking in the ground in ways we have never considered before," added Conyers.

Via: Discovery Channel