North Korea's underground nuclear test may reveal key clues about how close it is from having a nuclear weapon capable of striking the United States or its allies.
Hoping to capitalise on a rare opportunity to gauge North Korea's nuclear capabilities, intelligence and military officials are scrambling to glean data to answer three big questions: how powerful was the device, what sort of device was it, and what progress does the test indicate the nation has made.
North Korea hailed the test as a "perfect" success, saying it used a device that was stronger and more advanced than those in its past two attempts. Add that to its successful rocket launch in December and the threat of a North Korea ready to strike at the United States, which it sees as its arch-enemy, would appear to be more real than ever.
The main thing intelligence officials want to discover is what kind of device was used. Was it a plutonium bomb, like the ones it tested in 2006 and 2009, or one that used enriched uranium?
James Acton, an analyst with the Carnegie Endowment for International Peace, said North Korea's plutonium stockpile is small and it would be difficult and expensive for the North to produce more. But a test using highly enriched uranium, which is cheaper and easier to produce, would raise the threat that North Korea can expand its nuclear arsenal quickly.
"A highly enriched uranium test would be a significant development," he said.
"Unfortunately, we don't yet have any evidence as to the device's design yield or whether it was made from plutonium or highly enriched uranium."
Finding that out is a race against time.
Joseph De Trani, former head of the National Counterproliferation Centre, predicted US intelligence would determine the size of the nuclear device in one to three days based partly on radioactive elements released into the environment.
Neighbouring Japan may provide some of those answers.
Its fighter jets were dispatched immediately after the test to collect atmospheric samples. Japan has also established land-based monitoring posts, including one on its north-west coast, to collect similar data.
The final intelligence task will be confirming or dismissing North Korea's claim that this time around it tested a smaller, more advanced bomb. That is important because if the North is to field a nuclear weapon on the tip of a long-range missile, it must be lightweight. Making this determination will also depend on what materials leaked from the test.