The underwater explorers who spent last week scouring the offshore continental shelf for signs of 19,000-year-old human habitation sailed back to Galveston empty-handed Saturday.
The crew of geologists, biologists and marine archeologists was hoping to find clues of human activity in the area during the last Ice Age, when they believe the Texas coastline extended 100 miles into the Gulf of Mexico.
The expedition did not turn up anything definitive, but the scientists did find what they believe to be signs of the ancient shoreline about 330 feet below the ocean's surface.
"A series of long vertical steps look like they may have been created by the movement of waves, which carve out a trough and deposit material farther up," wrote team member Todd Viola, who posted mission logs daily on the expedition's Web site. "This is the same profile we see on modern beaches."
Viola described the find as very exciting but noted further exploration would be necessary to verify the scientists' theory.
Last week's expedition, dubbed "Secrets of the Gulf," was headed by Robert Ballard, the oceanographer and explorer best known for his discovery of the Titanic in 1985.
The team traveled from Galveston to the Flower Garden Banks, the northernmost coral reef on the United States continental shelf, aboard the SSV Carolyn Chouest with the U.S. Navy's nuclear-powered research submarine in tow. It was the first expedition Ballard led from shore.
Using a shipboard television studio and satellite technology, the team transmitted live video feed to groups of scientists all over the country. They also produced five live informational broadcasts each day.
According to the mission logs, the short expedition was plagued by bad weather and technical difficulties that limited use of Ballard's underwater research capsule, Argus. When it finally entered the water, the remotely operated vehicle transmitted high-definition pictures of the ancient shoreline on the last day of the trip.
While Argus was out of commission earlier in the week, the team relied on images from the submarine. Two scientists at a time stretched out in the bottom of the 145-foot vessel and peered out of view ports to observe the ocean floor.
The submarine's unique construction - with wheels for driving along the seabed - allowed the scientists to scrutinize the reef from a depth of 40 feet.
The discovery of an active mud volcano created quite a stir, wrote submarine captain Rick Panlilio in a March 6 log entry.
"We imaged it first with our side scanning sonar and found a large crater about 50 yards across on the summit," he wrote. "The summit was about 160 feet up from the surrounding plane. On the sonar images, we could see a wisp of something trailing off the top of the mound.
"We thrusted the submarine down on top of the hill and crept toward the center and, ‘Eureka!' we found that the dormant volcano was highly active, with a constant jet of gas, brine and silt being ejected from a briny mud pool inside the crater. The rocky structure inside the crater was jagged and run through with small canyons where dense brine seeped out."
The submarine and its crew sailed back to Galveston on Saturday. The scientists returned to their labs, but the Navy crew will remain in port until they leave for their next expedition Thursday.
During their layover, Lt. James Krohne said the sailors would be taking a trip to the Johnson Space Center to compare notes with the astronauts.