No noble gas from North Korea blast
As the huge hall at Vienna's Hofburg Palace began to fill with 800 scientists, diplomats and journalists this morning, a line of children wove its way to the stage. Looking slightly nervous and each in some form of national dress, they opened this scientific conference on nuclear testing with touching songs about world peace.
Officially the conference aims to sum up how well science is doing in detecting, understanding and warning the world's politicians about an explosion anywhere in the world - and the likelihood that such an explosion might be a nuclear test.
Its tool is a scientific network that underpins the Comprehensive Nuclear-Test Ban Treaty (CTBT), which proponents argue has a key role in creating a world free of nuclear tests, and possibly, one day, a world free of nuclear weapons.
But there was one thing everybody in the room wanted to know. Had the network of sensors picked up radionuclides from the North Korean explosion two weeks ago? Seismologists here today say they are comfortable that explosion was a nuclear test, but detecting radionuclide evidence in the form of radioactive gas is the "smoking gun". And the big news here is that they have not found that signal.
What's more, scientists don't really seem to know why. One delegate, an expert on radionuclide detection from Sweden, told the conference how well the network performed after North Korea's nuclear test in 2006. Twelve days after that event the network picked up just a few hundreds of atoms of the noble gas Xenon 133 in Canada. He confessed to being "surprised" that this time round, so far, there has been nothing. He said he is sure the sensors are working properly. So why might there be no signal, and does it matter?
The eminent seismologist Professor Paul Richards from Columbia University implied it didn't matter so much. The network includes a range of technologies - using seismic, infrasound, hydroacoustic and radionuclide technologies precisely to give the world what he described as a "a quiver of arrows". Thus if one arrow doesn't hit the target, then others will; if one detection set-up sees no nuclear signature, others will. And his personal view is that this was most likely a nuclear test.
So was there a deliberate attempt by the North Koreans to contain the explosion? Or was the explosion contained by accident? Some larger yield nuclear explosions can apparently "melt" the rock around them, so less noble gas seeps out. Attempts to explain the lack of a noble gas signal remain educated guesses at the moment. The official line here is that all this highlights the need for more countries to ratify the Treaty, so that it can come into force, thus allowing on-site inspection teams to move in to check out such tests.
In the meantime, scientists here might be keeping their fingers crossed that something shows up soon, but they seem already to be resigned to the possibility that it may not.
Those in Washington and elsewhere who see no value in treaties such as the CTBT may view this differently, perhaps as a vulnerability. The window of opportunity to detect noble gases from the May blast is closing. One more week and it will be too late. The material will be too widely dispersed or no longer radioactive enough to pick up.
The children who sang this morning invited the audience to join their "circle of friends", and they imagined a Magic Song that might bring peace to the world. It would be easy to be cynical. But it is a message pretty much echoed by the Austrian foreign minister who, perhaps optimistically, described the monitoring network as "a promise of peace to our children".
In the end, the scientists here say their goal is to give the world the best data they have, and let politicians decide what to do about it. At least the data from this second north Korean blast reached key people soon enough that they were able to convene the Security Council on the same day. But the world waits to see what, if anything, will happen next.