SAN FRANCISCO -- The Coast Guard planned to call off its search early Thursday for an acclaimed computer scientist lost on the waters off Northern California even as some of the computer industry's top minds joined the hunt.

According to Microsoft's Jim Gray Summary Home Page, he is a researcher and manager of Microsoft Research's eScience Group.

Despite unusually good weather conditions, searchers have exhausted any area Jim Gray could have drifted or sailed after leaving for a solo sailing trip Sunday to scatter his mother's ashes at sea, a Coast Guard spokesman said Wednesday afternoon.

SLIDESHOW: Images Of Jim Gray

"If they were to even find a life raft, they would have located him in their search patterns," said Petty Officer 3rd Class Jonathan Cilley.

Coast Guard officials told NBC11's Garvin Thomas they are stumped.

"I really don't see what else we can do," a Coast Guard official said.

They said they have searched everywhere and everything possible.

Friends of Gray said they are prepared to hire private aircraft to continue the search if the Coast Guard calls off their efforts, Thomas reported.

Officials said the search would be halted at 1 a.m. Thursday if no significant development arose.

After several tips failed to lead to Gray, Sergey Brin, co-founder and president of Internet search giant Google Inc., and engineers at online retailer Amazon.com sought high-tech ways to find the missing sailor.

A cargo plane, a helicopter and six patrol boats dispatched by the Coast Guard have been scouring the Pacific since Monday for Gray, whose database innovations led to some of the most widespread technological innovations of the past 30 years.

Two tips to Coast Guard searchers that a sailboat was drifting off the Marin County coast just north of the city failed to turn up any sign of Gray or his 40-foot yacht, Tenacious, Cilley said.

Brin was exploring whether recent satellite imagery provided for the company's popular Google Earth mapping software could be used to spot Gray's boat, a Google spokeswoman said.

Meanwhile, engineers at online retailer Amazon.com were determining whether the artificial intelligence software powering its Web site could be used to sift through aerial photographs of a wide swath of the Pacific.

Gray's research over the past 30 years allowed databases to sort quantities of information once considered too vast to manage, leading to the creation of both online shopping and Web-based mapping programs.

"The bad news is I fear we're not going to be successful," said Ed Lazowska, the Bill and Melinda Gates chair of computer science at the University of Washington, who has been brainstorming solutions for finding his longtime friend with contacts at Google and Amazon.

The difficulty of getting access to satellite photographs taken recently enough and at a resolution high enough to spot a sailboat meant that the Coast Guard's physical search for Gray was still the most likely way to locate him, Lazowska said.

The head of the Coast Guard, Adm. Thad Allen, said search crews had taken wind speed and ocean currents into consideration as they tried to pinpoint where Gray might have drifted.

"Our local commanders have pretty much saturated the area with search units," Allen said Wednesday in an interview with The Associated Press during a visit to San Francisco.

Gray, 63, of San Francisco, was last heard from on Sunday morning, shortly after he set out from San Francisco for the shark-infested waters of the Farallon Islands, about 25 miles west of the Golden Gate Bridge.

Signals from the emergency beacon on the longtime sailor's vessel have not been detected by rescuers, who expanded their search area Wednesday to cover 40,000 square miles from Monterey Bay to Oregon and more than 140 miles out to sea.

Gray received the A.M. Turing Award -- the "Nobel Prize of computer science" -- in 1998, several years after founding Microsoft's Bay Area Research Center in San Francisco, which he manages. His earlier research paved the way for automatic teller machines and computerized airline reservations.

More recently, he turned his attention to astronomy, using the same technology he used to chart the earth to create the world's largest online map of the heavens, revolutionizing the study of space, colleagues said.

"He's an absolutely unique individual," said Alex Szalay, a professor of astronomy at Johns Hopkins University and Gray's partner in developing the Sloan Digital Sky Server. "He has so many contributions to so many fields. He has really almost single-handedly helped transform several areas of science."

Gray had planned the trip to scatter the ashes of his 97-year-old mother, who died last year. He was expected to return by Sunday evening.

He called his wife from his yacht that morning to say he was sailing out of cell phone range, the last time contact with Gray was made, according to the Coast Guard.

Coast Guard spokeswoman Lt. Amy Marrs called Gray's disappearance a mystery because the weather was good, he was in good health and the boat was equipped with radios and flares.

Friends who had been in recent contact with Gray said they were certain he had not intentionally harmed himself.

"Everyone's unbelievably distressed," said Lazowska, who said he has known Gray for 25 years and last exchanged e-mails with him Saturday. "I can't imagine this is anything other than an accident of some sort."