A Chinese research vessel's escape from pack ice after evacuating 52 people from a Russian ship trapped in Antarctica has shone a spotlight on the Asian power's growing polar ambitions at both ends of the Earth.
In the Arctic, China's strategic goals include the opening up of a "Northeast Passage" shipping route Beijing hopes will shave days off the journey from China to Europe, its biggest export destination.
And in the Antarctic, Beijing has mounted 30 expeditions and built three research bases, one at more than 4,000 metres (13,000 feet) altitude on one of the frozen continent's highest ice caps.
Experts say that, just as in the space race, China is playing a long game in polar exploration, with the expected territorial and natural resource benefits decades, even half a century, away.
"At the moment, the only Antarctic resources that are really up to exploration are the marine living resources in the Southern Ocean," said Donald Rothwell, a professor of international law at Australian National University who co-edited a book on Antarctic security.
But while mining is banned until 2048 at the earliest under the Antarctic Treaty "some have observed China's development of its Antarctic interests allow it to be well-positioned if there is a change in the circumstances", he told AFP.
Rapid progress by latecomer
The 1959 agreement designates the icy continent as a scientific preserve and bans military activity.
Just as China got a late start in the space race, the world's second-largest economy did not sign onto the treaty until 1983, but has made stunning headway in the three decades since.
The Xue Long, or Snow Dragon, icebreaker was on a 155-day mission to construct a fourth Chinese station and survey a site for a planned fifth when it went to help the trapped Russian ship Akademik Shokalskiy last week.
Its helicopter evacuated 52 people from the vessel, which the state-run Global Times said had once again confirmed "China's national progress".
"It is China's growing industrial capacity that empowers Xue Long to perform such a rescue operation," it said. The ship later became stuck itself, but broke free to open water on Tuesday.
A new, more powerful icebreaker capable of clearing through floes 1.5 metres thick is under construction with completion due by 2015, according to the official Xinhua news agency.
Beijing is devoting an annual $55 million to Antarctic research and exploration, estimates Anne-Marie Brady, a professor at the University of Canterbury in New Zealand, up from $20 million a decade ago.
That is still well short of the estimated $300 million Washington spends on its Antarctic programme every year, and China's presence still lags other countries.
Argentina has 13 facilities on the continent, Russia 12 and the US six -- and under the Antarctic Treaty there are limits on new territorial claims or enlarging existing ones.
Concerns over territory
But China's moves at the ends of the earth have drawn concern from critics who say the agreement's territorial aspect is poorly enforced.
Some of the Chinese bases are within an expanse belonging to Australia, which claims 42 percent of the continent and established the first permanent Antarctic base in 1954.
"We risk getting left behind," the Australian Strategic Policy Institute warned in an October 2013 report.
"China, a relative newcomer, is proposing its third station in the (Australian Antarctic Territory). We've no presence at all in the neglected eastern sector. Effective occupation as a measure of sovereignty might be questioned."
Beijing's foreign ministry spokeswoman Hua Chunying did not directly address the issue of a possible territorial claim when asked Tuesday, but told reporters: "We hope that the international community can work together to jointly maintain the peace and stability of the Antarctic."
China supported "the peaceful use of resources in the Antarctic for the benefit of sustainable development for humankind", she added.
On the other side of the globe, China has made five expeditions to the Arctic and last May gained observer status in the Arctic Council, giving it a voice in deliberations over the future of the northern polar region.
With the Arctic ice melting, China could benefit from a shipping lane running north of the Asian landmass and south to Iceland -- heavily courted by China in recent months -- and the rest of Europe.
A Chinese merchant ship made the country's maiden voyage along the route in August.
Like Antarctic mineral exploration, commercial development is unlikely to take place for decades, yet it is noteworthy that Beijing is already making moves, said Rothwell.
"China's interest in Iceland can be seen as strategic if only because Iceland could prove to be a very pivotal shipping hub into the future -- especially if the Arctic ice melts," he said.
The Xue Long's rescue mission will have given China "a great deal of kudos in the Antarctic community", he added.
"All of that suggests to me that China is gaining a strong foothold and gaining great credibility in Antarctic affairs."