Argentine authorities received a few blips of hope in their effort to find a three-decade old submarine – and 44 crewmen – that suddenly stopped communicating during a routine mission on Wednesday.
That hope came in the form of seven signals to a satellite, which defense officials believe may have been attempts to communicate. Contact wasn't made and nothing was transmitted, but the signals, if from the sub, are the first signs of life from the ARA San Juan.
"We received seven satellite calls that likely came from the submarine San Juan. We are working hard to locate it," Argentina's Defense Minister Oscar Aguad tweeted. "To the families of the 44 crew members: We hope you'll have them home soon."
The calls came into different bases on Saturday between 10:52 a.m. and 3:42 p.m., according to CNN. The shortest was four seconds; the longest 36.
It was unclear Sunday whether authorities could use the signal attempts to determine the sub's location. A U.S. company that specializes in satellite communication is trying to help the Argentines pinpoint the location of the vanished sub.
The communications company is another addition to a growing international search mission combing the waters of the Atlantic and listening to all frequencies for signs of the sub.
The diesel-electric ARA San Juan was returning to its base south of Buenos Aires after a routine mission to Ushuaia, near the southern tip of South America on Wednesday. Then, suddenly, it went silent.
Complicating matters: strong winds and high waves that were battering search-and-rescue ships.
The Argentine government had received logistical help from several governments, including Britain, Chile and the United States. The U.S. Navy had sent several assets to help, including vehicles capable of conducting underwater rescues.
The Argentine navy has said the San Juan has multiple ways of communicating, as well as ample food and oxygen. Its protocol is to surface if there's a communications blackout.
"What we interpret is that there must have been a serious problem with the communications (infrastructure) or with the electrical supply, cables, antennae or other equipment," navy spokesman Enrique Balbi said, according to the Associated Press.
Worried relatives had gathered at the submarine's base, where they hoped to hear updates.
"We are praying to God and asking that all Argentines help us to pray that they keep navigating and that they can be found," Claudio Rodriguez, the brother of one of the crew members, told the local Todo Noticias TV channel, according to the AP. "We have faith that it's only a loss of communications."
News of the stricken submarine had even reached the Vatican. Pope Francis, an Argentina native and the former archbishop of Buenos Aires, offered his "fervent prayers for the 44 officers aboard the ARA San Juan" in a message released on his behalf Saturday by Cardinal Pietro Parolin, the Vatican's secretary of state, according to CNN. Francis "asks that his closeness be conveyed to their families and to the military and civil authorities of the country in these difficult moments."
Those family members and the Argentine government were facing a cruel fact of submarine life. The vessels are often among a country's most expensive and complex military assets – and, during accidents or times of crisis, their most vulnerable.
Over the years, several submarines have vanished, often igniting mysteries that lasted decades.
On May 27, 1968, the USS Scorpion failed to return to port, unexplainedly sinking 11,220 feet beneath the Atlantic Ocean along with its 99 crewmen and two nuclear torpedoes, according to USA Today. A Navy inquiry found that the cause of the sinking "cannot be definitively ascertained" – and the cause of the sub's demise remains fuzzy decades later.
Theories abound, of course: a torpedo self-fired into the ship, destroying it from the inside, or a battery exploded, inflicting critical damage. The Navy has routinely tested the water around the ship for radioactivity, according to USA Today, but has denied a proposal by civilian marine disaster experts to investigate the wreckage.
In August 2000, the Russian nuclear submarine Kursk suddenly sank during a planned and closely monitored Russian military exercise, killing all 188 sailors aboard, according to the New York Times. It was hours before the Russian government even knew something was amiss.
The most likely explanation was that fuel in a torpedo detonated, setting off a chain reaction in a sub once deemed unsinkable. The Russians have said the Kursk used an outdated and unstable hydrogen peroxide propellant.
Conspiracy theories abound, and at least one real-life horror story was verified: Not all of the sailors died in the initial blast, according to the New York Times.
For hours, some fought fruitlessly to survive.
"13:15," wrote Lt. Capt. Dimitri Kolesniko, the commander of the turbine room, noting the military time. "All personnel from compartments six, seven and eight moved to the ninth. There are 23 of us here. We have made this decision as a result of the accident. None of us can get out."