Only rarely does a group tour come along that makes the most fiercely independent traveler's heart beat faster -- a journey so complex that you couldn't pull it off alone, and so unusual that you can't help yearning to go.
An intriguing example takes place next summer in a remote part of the Pacific Ocean: It's a chance to join a team of experts searching an uninhabited coral atoll for traces of lost aviator Amelia Earhart.
The island is Nikumaroro, and it's not the one that Earhart was aiming for when she and her navigator, Fred Noonan, vanished into the Pacific in July 1937 on their around-the-world attempt.
They took off from New Guinea, heading east, and were scheduled to refuel on a mid-ocean speck called Howland Island. They never got there.
Their disappearance spawned a flock of theories, theories as simple as a crash to those as complex as capture by the Japanese military on the eve of World War II, to those as far-fetched as being kidnapped by extraterrestrials.
Plus one that may be the real answer: an emergency landing on a different island, where Earhart and Noonan might have survived for a time.
That hypothesis is the heart of this trip, June 17 to July 3, 2015. It's co-sponsored by the International Group for Historic Aircraft Recovery (TIGHAR), which has been looking for Earhart for 25 years, and by Betchart Expeditions of Cupertino, Calif., a travel company known for unusual trips with a strong scientific component.
Nikumaroro Island is the most likely candidate, said Tom King, senior archaeologist with TIGHAR, who will help lead the 2015 Betchart trip.
Bigger than Howland Island, "Niku'' – also known as Gardner Island -- would have been the logical landing place for Earhart and Noonan once they'd missed their original target, King said.
TIGHAR has already discovered promising traces on Nikumaroro, including a woman's shoe, part of a woman's compact with bits of rouge, and fragments of glass from a 1930s cosmetic jar that once held freckle cream -- significant because Earhart was a fair-skinned redhead and an international celebrity to whom looks were important.
"We think we're getting close,'' King said.
The TIGHAR/Betchart group will fly on Fiji Air from Los Angeles to Nadi, Fiji, then sail to Nikumaroro on the Reef Endeavour, a 130-passenger cruise ship.
Its course will loop northward out of Fiji, first to Rotuma Island, then to Funafuti atoll (the capital of Tuvalu), and finally to Nikumaroro, in the Phoenix Islands Protected Area.
The ship will return to Fiji via the small monarchies of Wallis Island and Futuna Island.
Thick vegetation on Nikumaroro makes the island difficult to get around on, the trip's planners say.
Getting ashore is no picnic, either: Passengers will be transferred to the island by glass-bottomed boat or the cruise ship's tenders.
They will disembark on the Nutiran Shore, a flattish, slippery platform of coral where Earhart's Electra aircraft might have been able to make an emergency landing at very low tide.
Some former residents – Pacific islanders who were part of a short-lived British colony on Niku – told TIGHAR researchers that they remembered seeing an airplane there, and some had salvaged small scraps of aircraft aluminum.
TIGHAR researchers determined the metal came from an Electra, but there is no way of proving – yet, anyway -- whether it was Earhart's.
A prewar photo shows what may be part of a landing gear sticking out of the shallows, but TIGHAR concluded that high tides would have washed any remains of the plane off the coral and into very deep water.
British colonial records show that human bones were found at what TIGHAR calls "7 Site'' – a natural clearing shaped like the number seven – but the remains were sent to Suva in 1940. King said TIGHAR still hopes they may have ended up in private hands or still be in museum storage there.
While at Nikumaroro, Betchart passengers can accompany TIGHAR team leaders to key locations and take photographs and GPS readings of any new discoveries.
Before and after Niku, time at sea will be filled with lectures by experts on oceanography, astronomy, geology, climate change, and the history and cultures of this part of the South Pacific.
Prices for the trip range from $7,195 to $10,995 per person based on double occupancy, plus a round-trip S group airfare of $1,595 on Fiji Air from Los Angeles to Nadi, Fiji.