over the last few days.
  The ruins are on the edge of the Empty Quarter of the Arabian Peninsula in the Dhofar region of Southern Oman. They surround the water well now known as Ash Shisar. That is near the Qara Mountains, where grew - and still grow - the trees that were a major source of the aromatic resin for the frankincense so prized in ancient times as a symbol of wealth and holiness and a substance used in embalming and fumigation. Myrrh is also a gum resin used in making incense.
  "There doesn't seem to be much question that we have discovered Omanum Emporium,"said Dr. Juris Zarins, the expedition's chief archeologist. "This site is very rich, no doubt about it."

'A Major Find'

  But Dr. Donald Whitcomb, an archeologist at the Oriental Institute of the University of Chicago, said some scholars suspect that Iram would be found not in Southeast Arabia but in the Northwest, perhaps near the Jordan-Saudia Arabia border. But he praised the discovery while reserving judgment on its interpretation.
  Dr. Ronald G. Blom, a geologist and specialist in spacecraft remote sensing at the Jet Propulsion Laboratory in Pasadena, Calif., said: "It's a major find. If this is not Ubar, it certainly was a very important place in ancient times."
   The idea of searching for the lost city of Ubar was conceived in 1981 by Nicholas Clapp, a Los Angeles filmmaker and adventurer. He was attracted to the mystery and romance of ancient Arabia that was rooted in the frankincense trade and especially intrigued to find that "virtually nothing is known of the trade at its source" there in the region of Ubar.
  When he learned of experiments demonstrating the application of space remote-sensing to archeological exploration, Mr. Clapp got busy and, with the help of Mr. Hedges, recruited a team of experts in several fields.

  Sir Ranulph Fiennes, a British polar explorer with close ties to the Sultan of Oman, Qaboos ibn Said, directed logistics for the expedition and helped arrange financing from Omani backers.

  Alan Jutzi, curator of rare books at the Huntington Library in San Marino, Calif., assisted with archival research. Dr, Zarins, a professor at Southwest Missouri State University in Springfield and a specialist in Arabian archeology, is still at the site directing the excavations.

  Analysis of the space images was directed by Dr. Charles Elachi, an assistant director of the Jet Propulsion Laboratory who developed an imaging radar system that has been flown on space shuttle missions. Working with him were Dr. Blom and Dr. Robert E. Crippen, also of the laboratory, which is operated by the California Institute of Technology for the National Aeronautics and Space Administration.

  The literature of Ubar was alluring, if not as informative as the team would have liked. Built by the legendary Shaddad ibn Ad as an "imitation of Paradise," the city was renowned for its imposing architecture, vast groves of fruit trees and fabulous wealth. The historian, Al-Hamdani, writing in the sixth century A.D., hailed Ubar as first among the treasures of ancient Arabia.

  In the Koran, Iram, possibly Ubar, is described as the "many columned city...whose like has not been built in the entire land. But it came to have a reputation and fate not unlike that of Sodom and Gomorrah in the Bible. Condemned for their sinful and unrepentant lives, the Koran relates, the people in Iram were destroyed by Allah.

Fall Into a Cavern

  Ubar's cataclysmic destruction, recounted also in the "Arabian Nights," must have occurred toward the end of the Roman period, historians say. At any rate, the expedition found evidence of its cause. The site's buildings were built over a large limestone cavern, which at some point in the distant past collapsed, plunging much of the city into a gaping hole. The ruins were eventually buried in drifting sand.
   Lost but not forgotten, Ubar was called "the Atlantis of the sands" by T.E. Lawerence, Lawrence of Arabia, who had planned to look for the site before his death. Sixty years ago, another British explorer, Bertram Thomas, apparently came close in his traverse of the Empty Quarter. He came upon a wide caravan track that his Bedouin companions spoke of as the "road to Ubar." He visited the Ash Shisar water hole, where he noted the ruins of a "rude fort," but he took it to be no more than a few hundred years old.
  That account and Ptolemy's map coordinates were about all Mr. Clapp had to go on when he turned for help to the computer-enhanced images from both satellites and a radar system flown on the shuttle. On its first test in 1981, the shuttle imaging radar detected previously unknown river beds beneath the sands of Egypt.
  As Dr. Blom recalled, Mr. Clapp telephoned and said, "If a city was buried in the desert, could you see it by this radar?" Once satisfied this was no crank call, Dr. Blom and others joined the effort, and arranged for the next shuttle radar flight, in 1984, to take aim on the region described in the Thomas account.

Detecting Ancient Tracks

  Despite some malfunctions, the radar did record a broad swath of the Empty Quarter. No buried ruins could be detected, but there were tracks of caravan routes. Manyof them ran for miles, disappeared under a vast sand dune, then emerged from the other side. These, it was concluded must be extremely ancient.
  "I was surprised to find that we were able to readily detect ancient tracks in the enhanced images," Dr. Blom said.
  Then the J.P.L. scientists obtained and processed images from the American Landsat spacecraft and the French SPOT satellite. The black-and-white SPOT photography is the most detailed available to civilian users. The Landsat mapping images record terrain in visible light and otherwise invisible nearinfrared wavelengths, which geologists find to be revealing of rock and soil conditions.

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