Sandro Vannini / National Geographic

This "shabti," or funerary servant figure, is from the antechamber of Tutankhamun's tomb. Shabtis were inscribed with a spell from the Book of the Dead that ensured the king would do no forced labor in the afterlife. The figure is part of the "Tutankhamun: The Golden King and the Great Pharaohs," an exhibit that is winding up its U.S. tour in Seattle.

Two major exhibits of ancient artifacts relating to the best-known figures from ancient Egypt, King Tut and Cleopatra, are in the last stages of their U.S. tours — and their departure could signal the end of an era.

"Cleopatra: The Exhibition" opened at the California Science Center in Los Angeles on Wednesday, while "Tutankhamun: The Golden King and the Great Pharaohs" began its run at the Pacific Science Center in Seattle today. By the end of next year, the more than 250 artifacts from the two exhibitions will be back in Egypt, possibly for good.

The return to Egypt marks the end of a Tut-centric "Comeback Tour" that began back in 2005 and sparked the kind of enthusiasm that was seen back in the 1970s, during an earlier Tut exhibit. Like that 1976-1979 "Treasures of Tutankhamun" show, millions have turned out to see the glittering gold and the 3,300-year-old artifacts associated with the boy-king's short reign. More than 90,000 advance tickets already have been sold for this year's Seattle exhibit.

Transplanting Tut-mania
Among the featured objects in Seattle are a 10-foot-tall statue of the pharaoh, Tut's golden sandals and the golden funerary mask of King Psusennes I. (Tut's golden mask, which was such a hit since the '70s, was judged too fragile and valuable to travel out of Egypt this time around.)

After Seattle, the more than 100 artifacts will go to the Grand Egyptian Museum in Giza, which is currently under construction and due for completion in 2015. At one time, Egyptian officials saw the revenue generated by traveling exhibits as a means to cover the museum construction costs. But last year's revolution dealt a heavy blow to the country's tourist industry, and now officials think it's more important to bring museumgoers to the treasures in Egypt than to bring the treasures to museumgoers outside Egypt.

"They're eager to see these [artifacts] return to Egypt," said Bryan Harris, vice president of sales and marketing for Arts and Exhibitions International, which helped organize the Tut tour. And they're eager for tourists to follow Tut's trail.

That came through loud and clear during a Seattle news conference on Wednesday. "Please, we need your help," Antiquities Minister Mohammed Ibrahim said. "We need you to support our revolution. We need you to support our movement toward peace and democracy."

Cleopatra's sunken treasures
The stars of the Tut exhibit are artifacts that were found 90 years ago in a long-hidden tomb by British archaeologist Howard Carter, but it's a different story for the more than 150 "Cleopatra" artifacts now on display in Los Angeles. They were brought to the surface just in the past few years during underwater excavations at the sunken sites of Alexandria, Heracleion and Canopus.

"All those artifacts were completely covered by sediment," French archaeologist Franck Goddio, leader of the underwater excavation, told me.

Slideshow: In search of Cleopatra’s palace

Christoph Gerigk / AP

Divers explore the submerged ruins of a palace and temple in Alexandria's harbor.

Launch slideshow

The project made a splash, so to speak, when the "Cleopatra" tour was first announced a couple of years ago, and since then it's been on display in Philadelphia, Cincinnati and Milwaukee. One more U.S. city, yet to be determined, could join the list after Los Angeles. But by the end of 2013, the statues, jewelry, coins and other items will be distributed among several Egyptian museums, Goddio said. Egyptian authorities are considering the construction of an underwater museum in Alexandria Harbor, and if that project goes forward, "all the artifacts will go in that museum," he said.

Goddio said the artifacts recovered so far suggest that Hellenistic Egypt, the culture in which Cleopatra lived during the first century B.C., was less Greek and much more Egyptian than experts previously thought. "The Egyptian sensitivity is much stronger than what it was thought to be at that time," he said. And that's all the more reason for present-day Egyptian officials to want those treasures back in their home country.

Fortunately, Goddio and others have been able to continue their work amid all of Egypt's political changes, including the run-up to this week's presidential elections there.

"Up to now, the authority has not changed," he told me, "and it's not expected that there will be any change from a scientific view." So even though the long-traveling treasures may be going home for good, there might be fresh archaeological finds available for future road trips.

And after all, Egypt isn't the only place that offers archaeological wonders. Just this month, for example, Penn Museum opened a "Maya 2012" exhibit featuring sculptures and replicas of monuments from the Maya civilization.

Harris acknowledges that Egypt doesn't hold a monopoly on ancient mysteries and marvels. Nevertheless, he says there's something special about old King Tut. "An exhibit like 'Tutankhamun' is really like lightning in a bottle," he told me. "For some reason, Egyptian culture, and particularly Tutankhamun, seems to captivate the imagination more than any other. ... To be honest, there's only one."

More about Egyptian treasures:

• 'King Tut' makes last stop in Seattle
• Spots on Tut's tomb suggest hasty burial
• Slideshow: King Tut's treasures in context
• Mummies and statues point to Cleopatra's tomb
• Video: Book paints Cleopatra as 'shrewd' and 'brutal'

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.