[meteorite-list] Satellites Hunt For Buried Treasure

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:01 2004
Message-ID: <200307091927.MAA10549_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/news/news.jsp?id=ns99993923

Satellites hunt for buried treasure
Hazel Morris
New Scientist
July 9, 2003

In a first for radar sensing, researchers have proved the technology can
locate and identify buried objects. Their technique could be used in the
hunt for archaeological artefacts smothered by sand or networks of
underground buildings, or even to peer below the surface of Mars.

Scientists have long suspected that microwave radar from satellites could
"see" below the surface of very dry ground. Many were startled when images
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 has been no proof that these images really do show
underground objects. Researchers were unsure how radar is affected by
underground features, and no one had ever used radar sensing to detect
objects they knew were there. So although the images looked convincing, it
was possible that they simply showed varying soil properties or surface
slopes.

Dan Blumberg and Julian Daniels of the Ben Gurion University of the Negev in
Israel decided to test the idea. They buried flat squares of aluminium at
different depths under the sand in the Negev desert, then flew an aircraft
over the area to carry out radar sensing of the layers beneath the surface.

By comparing the radar results with the squares' known positions, the
researchers showed that the patterns detected by the radar really did show
the buried pieces of metal. "Now we have systematic proof," Blumberg told
New Scientist. "Buried objects can be detected from airborne systems."

That suggests the satellite images show real structures, too. Blumberg says
the result confirms that ancient river routes do lie hidden beneath
centuries of Saharan sand. Their location ties in with that of the oases and
temporary lakes around which desert peoples build their communities.
"Mapping river channels buried in sandy areas can improve our understanding
of the geological and climatic history of the region," says Daniels.

So far, the researchers have only looked for objects buried up to 40
centimetres deep. But now that they have proved the technique works, they
are planning studies with different types of object, buried deeper.

For their experiments, they use microwaves of the longest possible
wavelength, called P-band (see Graphic). 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, perhaps
up to 9 metres down.

"Using the P-band is quite new," says Andrew Wilson, a remote-sensing expert
for Britain's Natural Environment Research Council. "It can penetrate the
ground farther, so it would be good at revealing archaeological objects."

Blumberg hopes that as well as archaeological remains, the method will in
time be used to find fossils and geological structures. There could also be
military or humanitarian applications. The resolution would probably be too
low to pick up individual landmines, but it could show underground buildings
or pipes, or perhaps even mass graves.

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. The surfaces of some planets and moons
fit the bill too, he points out. He hopes P-band radar might be used to
reveal structures such as water channels below the dry, frozen surface of
Mars.
Received on Wed 09 Jul 2003 03:27:54 PM PDT


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