(CNN) -- Seventy-four passengers trapped aboard an expedition vessel in the Antarctic for nearly a week will have to wait even longer as a rescue ship slowly makes its way through thick ice and snow.
The Australian icebreaker ship Aurora Australis was 11 nautical miles away from the Russian-flagged Akademik Shokalskiy early Monday, according to the Australian Maritime Safety Authority.
"It's hard to tell if it makes it through," said Lisa Martin, a spokeswoman for AMSA. "There are snow showers in the area that are causing bad visibility; conditions are deteriorating."
Visibility was only about 200 meters (656 feet), not enough to assess whether the ice breaker can cut through.
"It's a wait-and-see operation. It's a very complex situation," Martin said.
This attempt by the Aurora Australis follows one by the Chinese icebreaker Xue Long, or Snow Dragon, which was just six nautical miles away from the trapped vessel when it couldn't get any closer due to unusually thick ice.
The Snow Dragon went back to open water but remains in the area to provide support, said Andrea Hayward-Maher, another spokeswoman for the AMSA. The Chinese ship has a helicopter on board that could assist in evacuation.
"We are waiting on the Aurora Australis to tell us if it can make its way through the ice. If it can't, then we will be shifting towards the helicopter, and obviously that is weather dependent," Martin said.
A French icebreaker was also en route to assist, but AMSA called off that vessel's mission Saturday after it became clear that ship wouldn't get farther than the Chinese boat. Also, the French and Chinese ships can break ice only about 1 meter (3.3 feet) thick, whereas the Australian ship can pierce through floe about 1.35 meters (4.4 feet) thick.
"Some reports say that the ice is at least 2 meters (6.6 feet) deep. It's a possibility that the Aurora Australis might not be able to break through that type of ice," Hayward-Maher said.
Chipper updates continue
Throughout the week trapped passengers have been giving mostly positive updates via YouTube, greeting family members and telling everyone that they're having a great time.
"It's my birthday today -- it couldn't be a better day to have a birthday with my 80-something new friends," one female passenger declared cheerfully while standing on the ice in front of the stranded vessel.
"This afternoon we're gonna have some singing on the ice, which should be fantastic as well," another female passenger adds.
"It's absolutely spectacular here; it's like this magical winter wonderland," she declares with a smile as she waves her arms to point out the vast expanse of snow and a foggy sky.
The group continues to do research and finds activities to stay occupied, but there is growing concern that blizzard conditions could worsen over the coming days, according to expedition leader Chris Turney, an Australian professor of climate change.
The rescue icebreakers were battling the planet's coldest environment while trying to reach the Akademik Shokalskiy ship, whose 74 researchers, crew and tourists remained in good condition despite being at a frozen standstill since last Monday.
"The vessel is fine, it's safe and everyone on board is very well," Turney said. "Morale is really high."
The ship got stuck in the ice 15 days after setting out on the second leg of its research trip.
According to Turney, a professor at the University of New South Wales, the ship was surrounded by ice up to nearly 10 feet (3 meters) thick. It was about 100 nautical miles east of the French base Dumont D'Urville, about 1,500 nautical miles south of Hobart, Tasmania.
On Christmas morning, the ship sent a satellite distress signal after conditions failed to clear.
The crew had a "great Christmas" despite their situation, Turney told CNN. He said crew members have used the delay to get more work done.
"We've just kept the team busy," he said.
The expedition is trying to update scientific measurements taken by an Australian expedition led by Douglas Mawson that set out in 1911.
The expedition to gauge the effects of climate change on the region began November 27. The second and current leg of the trip started December 8 and was scheduled to conclude with a return to New Zealand on January 4.
Turney said the ship should still be back in New Zealand on time.
CNN's Naik Bharati, Isa Soares, Sara Mazloumsaki and Brian Walker contributed to this report.