Professor Dan Blumberg in the field: Being able to really know what lies below the earth’s surface is an exciting prospect that challenges our imaginations.It sounds like a backwards proposition, but new research shows that we can find out more about what is buried beneath the earth’s surface by launching a satellite into the sky.
The work by the two professors from Ben-Gurion University of the Negev, Dan Blumberg and Julian Daniels has shown that radar-sensing technology from satellites is able to both locate and identify buried objects.
Blumberg’s finding that “buried objects can be detected from airborne systems,” as he puts it, opens up a long list of exciting possible applications.
“Being able to really know what lies below the earth’s surface is an exciting prospect that challenges our imaginations,” Blumberg told ISRAEL21c. “It’s similar to our fascination with X-rays and study of what lies under our skin, inside the human body.”
If harnessed properly, this technique could be used to discover major archaeological sites that are buried under layers of sand and rocks, identify areas in which ideal conditions exist for certain kinds of agriculture, and to learn more about what lies below the surface of other planets.
Scientists have long hypothesized that microwave radar from satellites could “see” below the surface of very dry ground, according to a recent article in New Scientist Magazine, that took note of Blumberg’s breakthrough. Images gathered from a shuttle mission in the 1980s revealed what appeared to be ancient river drainage patterns below the eastern Sahara desert. Since then there have been other intriguing finds, including ring structures buried under Antarctic ice that look like meteorite craters or the remains of subglacial volcanic eruptions.
But until now there had been no clear evidence as to whether these images were in fact accurately detecting structures that lay beneath the surface of the earth. Blumberg and Daniels put the hypothesis of radar sensing to the test. First they built a theoretical model, and then a physical model. Finally, they rented a plane and placed aluminum squares under the sand in the Negev desert at different depths. They flew the plane equipped with a radar sensor and checked the area they were flying over.
The results matched up: when they compared the radar results with the squares’ known positions, the researchers showed that the patterns detected by the radar were indeed the actual locations of the buried metal squares.
This suggests the satellite images show real structures, too. Blumberg believes that the result of his experiments confirms that ancient river routes do lie hidden beneath centuries of Saharan sand, as radars have shows. Their location ties in with that of the oases and temporary lakes around which desert peoples build their communities.
Now that Blumberg and Daniels have proven that radar can ‘see’ objects buried up to 40 centimeters under the ground, they intend to engage in further studies with various kinds of objects, buried even deeper under the ground. For their experiments, they use microwaves of the longest possible wavelength, called P-band. At the moment, satellites generally use microwaves with shorter wavelengths because the resolution is better. But P-band radiation can penetrate farther underground, so Blumberg hopes that adding it to satellite sensors will allow them to probe deeper.
Blumberg dreams that along with as archaeological remains, the method will in time be used to find fossils and geological structures, and hopes that there will be additional useful applications as well.
“One important application and issue of scientific interest is actually the ability to map soil water content using satellite data,” he said. “We have been doing a lot of work in the past three years on improving our ability to map the soil water content in agricultural fields in the arid environment using P-band data and shorter wavelength (C-band) images from space.”
An even more exciting possibility would be if radars could detect buried landmines and other underground military ordinance, which could be removed, saving thousands of lives. The question that always comes up is military ordinance. The main snag is that radar can only penetrate the ground in very dry areas, because liquid water tends to absorb the radiation. But Blumberg says that 15 per cent of the Earth’s surface is dry enough for the method to work, including the Antarctic and deserts.
Blumberg, 42, was born in South Africa and immigrated to Israel when he was eight. After completing undergraduate studies at BGU, he received a PhD from Arizona State University in planetary geology. His interest in other planets leads him to hope that one day, the method he is developing could be used to explore what lies below the surfaces of various planets and moons. He also hopes P-band radar might be used to reveal structures such as water channels below the dry, frozen surface of Mars, and has published a paper about such a possible application.
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