The hunt for Malaysia Airlines Flight 370 has penetrated beneath the waves as searchers race to catch pings from the missing plane's flight data recorders before they fall silent.
But the area of the southern Indian Ocean where British and Australian naval ships are deploying sophisticated listening technology remains nothing more than an educated guess at where the plane may have hit the water.
The British Royal Navy survey ship HMS Echo and the Australian naval supply ship Ocean Shield began searching the ocean's depths along a single 240-kilometer (150-mile) track Friday, said retired Air Chief Marshal Angus Houston, the head of the Australian agency coordinating the search efforts.
The Ocean Shield is equipped with high-tech gear borrowed from the United States: the TPL-25, a giant underwater microphone that will listen for the pings from the flight data recorders, and the Bluefin-21, an underwater robot that can scour the ocean bed for signs of wreckage. The HMS Echo also has advanced sensor equipment.
Time is running out in the efforts to detect the pings as the batteries that power the recorders' beacons are expected to expire in the coming days.
"If they do find it, I think it'll be remarkable," said Bill Schofield, an Australian scientist who worked on developing flight data recorders.
Nearly four weeks have passed since the jetliner vanished with 239 people on board. With investigators still apparently stumped by the case, information in the flight recorders could help them unravel the mystery of what happened the night the plane dropped off radar.
But there are no new clues behind the area where the underwater search is concentrated. It's based on the same kind of analysis of radar, satellite and other data that investigators have used to determine a series of shifting search areas in recent weeks.
"The area of highest probability as to where the aircraft might have entered the water is the area where the underwater search will commence," Houston said at a news conference Friday. "It's on the basis of data that arrived only recently, and it's the best data that is available."
'Just a guess'
Until searchers can find a confirmed piece of debris from the plane, which would give them a clearer idea of where the main bits of wreckage might be located, there is no certainty the technology is being pointed in the right direction.
"Really the best we can do right now is put these assets in the best location - the best guess we have - and kind of let them go," U.S. Navy Cmdr. William Marks told CNN. "Until we get conclusive evidence of debris, it is just a guess."
Searching with the pinger locator trailing from a ship is painstaking work, another U.S. Navy official said.
"It is a very slow proceeding search, 2 to 3 knots depending on the depth," said Capt. Mark M. Matthews, director of ocean engineering. But since it doesn't rely on daylight, the device can keep searching 24/7.
"It's going to take time," Matthews said, adding that the Bluefin-21 robot would only be deployed if the searchers get a clear fix on the beacons sending out the pings.
The ocean in the general area where the search is taking place is between 2,000 meters and 4,000 meters (6,500 feet and 13,000 feet) deep. The pinger locator can search as deep as 20,000 feet (6,100 meters), according to the U.S. Navy.
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As the community reels from a shooting rampage at Fort Hood, investigators are grappling for answers on why Spc. Ivan Lopez opened fire against fellow soldiers.
Investigators are looking at a possible altercation with a fellow soldier "that immediately preceded the shooting," said Lt. Gen. Mark Milley, the post's commanding general.
They are still piecing together the answer, but seem to be honing in on at least one thing that they say might have made the 34-year-old pull the trigger.
"We have very strong evidence that he had a medical history that indicates an unstable psychiatric or psychological condition. (We're) going through all records to ensure that is, in fact, correct. But we believe that to be the fundamental underlying causal factor," Milley said Thursday.
Investigators say they haven't found any links to terrorism so far.
Two journalists working for The Associated Press have been shot in Afghanistan, one of them fatally, the news agency said Friday.
The Associated Press said the slain journalist was Anja Niedringhaus, 48, an internationally acclaimed German photographer. She was shot in the country's eastern Khost province.
The second journalist targeted by the gunman was Kathy Gannon, a Canadian reporter based in Islamabad, the AP said. She is said to be in a stable condition and is receiving medical care.
"Anja and Kathy together have spent years in Afghanistan covering the conflict and the people there," said AP executive editor Kathleen Carroll, speaking in New York. "Anja was a vibrant, dynamic journalist well-loved for her insightful photographs, her warm heart and joy for life. We are heartbroken at her loss."
In a letter to AP staff Friday morning, chief executive Gary Pruitt also praised her courage and skill, describing her as "spirited, intrepid and fearless, with a raucous laugh that we will always remember."
The two women were traveling in their own car in a convoy of election workers delivering ballots in Khost province, protected by the Afghan National Army and Afghan police, the news agency said.
A unit commander walked up to their car as it waited to move, yelled "Allahu akbar" - "God is great" - and opened fire on them in the back seat, the AP said. He then surrendered to the other police present.
The reason for the attack is unclear, but police have arrested the suspected shooter and the case is under investigation, Baryalay Rawan, a spokesman for the Khost provincial governor, told CNN.
The attack came amid heightened security on the eve of Afghanistan's presidential and provincial elections.
The third presidential vote since the fall of the Taliban in 2001, this year's elections mark the first democratic handover of power in the fragile country, with current President Hamid Karzai - who is term-limited by the constitution - handing over the reins.
The Taliban have vowed to disrupt the elections and punish anyone involved in them.
A series of attacks in the capital, Kabul, and elsewhere has marred the run-up to the elections.
On Wednesday, a suicide bomber blew himself up at the entrance gate to the Interior Ministry in Kabul, killing six Afghan police officers, Interior Ministry spokesman Sediq Sediqqi said. The Taliban claimed responsibility for the attack.
A day earlier, a provincial council candidate and nine of his supporters were killed by the Taliban in northern Sar-e-Pul province, said the province's deputy police chief, Sakhidad Haidari.
Other journalists killed
Last month, the names of two more journalists were added to the list of those killed in Afghanistan.
Sardar Ahmad, one of Afghanistan's most prominent journalists and a senior reporter for Agence France-Presse, was among nine people killed in an attack on the Serena Hotel in central Kabul.
That attack came less than two weeks after Swedish Radio correspondent Nils Horner was shot dead in broad daylight on a Kabul street.
In his letter to AP staff, Pruitt said: "As conflict spreads throughout regions of the world, journalism has become more dangerous. Where once reporters and photographers were seen as the impartial eyes and ears of crucial information, today they are often targets."
The Committee to Protect Journalists highlighted the risks faced by journalists, particularly women, in Afghanistan in a piece published in February.
Some fear those risks may increase as the planned withdrawal of NATO combat forces, including U.S. troops, looms at the end of the year.
The NATO-led International Security Assistance Force had just over 51,000 troops, from 48 different countries, in Afghanistan as of Tuesday. Of those, the vast majority - about 33,500 - are from the United States.
Karzai has refused to sign an agreement to keep foreign security troops in the country after 2014.
But Gen. Philip Breedlove, NATO's supreme allied commander Europe, told CNN's Christiane Amanpour this week that he anticipates international forces will remain in Afghanistan after the currently scheduled withdrawal.
"I think you will see a very large ISAF combat mission changed to a smaller but continued resolute support, train, advise and assist mission at the end of the year," he said. "NATO's mission doesn't end (after 2014); NATO's combat mission ends, but our train, advise, assist mission begins, and this is very important to remember."
The three leading presidential candidates - Abdullah Abdullah, Zalmai Rassoul and Ashraf Ghani - have told CNN that they are in favor of signing a deal.
Abdullah, who was a vocal critic of the Taliban during their years in power, was a previous Karzai ally and served in his government as foreign minister. But in later years, he has been a thorn in the side of the outgoing President. He is seen as a relatively liberal candidate and advocate of women's engagement in public life.
Rassoul is seen as the establishment candidate. A Karzai ally, he received the backing of the current President's brother, Qayum, who withdrew his candidacy and endorsed the former foreign minister. Rassoul has a reputation for honesty, despite his years in an administration plagued with accusations of graft.
The third key contender, Ghani, is a former U.S. citizen and academic who gave up his passport to run for the Afghan presidency in 2009. He is seen as a moderate, with experience in development, but his past links to the United States may lessen his chances if voters see him as an outsider.
NATO Secretary General Anders Fogh Rasmussen, speaking Wednesday in Belgium, said the latest briefings from NATO commanders show that despite the Taliban's threats, overall violence across Afghanistan "is lower now than at any time during the last two years."
Rasmussen praised the work of Afghan security forces, which have taken over many responsibilities from the NATO-led International Security Assistance Force, saying they had "demonstrated commitment, courage and professionalism" during preparations for the elections.
In "the nation's salad bowl," as California's Central Valley is often called, fresh produce grows in abundance.
But for many area residents, healthy food is out of reach.
"Here we are in this agriculturally rich area and yet people who live here and work here are hungry, are impoverished," said Sarah Ramirez, an educator who grew up in the area.
"(Some) are working in the fields that feed the entire country and then they don't have the resources to support them and their health. It's heartbreaking."
For the last two years, Ramirez has been on a mission to build a healthier community in her impoverished hometown of Pixley.
She and her husband launched Be Healthy Tulare, a grass-roots movement to collect produce that would otherwise go to waste and get it to neighbors in need. The group is named for the county where Pixley is located.
"Looking outside and seeing trees just loaded with fruit, I was just feeling like, why aren't we connecting these pieces?" Ramirez said.
Twice a month, Ramirez and volunteers gather fruit and vegetables from farms and backyard trees. They glean from growers and residents who contact them about their excess produce. The group then provides the bounty to a local food bank that distributes it to families in need.
So far this year, Ramirez said, she and her group have collected and donated 20,000 pounds of produce.
See full story at CNN Heroes.