15 months after Malaysia Airlines Flight MH17 was shot down, a group of experts convened by the Netherlands have finished studying the crash. Their report explains what happened, and gives us a glimpse at the advanced technical forensics they used to painstakingly recreate the attack.
One of the most striking reports from the first days of the MH17 investigation was how investigators were blocked from the crash site by armed pro-Russian fighters -- and when they were allowed in, how widely the wreckage of the plane was scattered. It didn't seem likely those fragments, scattered miles across a war zone, would give up specific answers very easily.
This week's report from the Dutch Safety Board is as specific as you can get, though. According to the Dutch, MH17 was shot down by a 9N314M-type warhead launched from a Buk missile system (Russia, for its part, disputes what type of warhead was used). Here are a few of the technologies they used to reach their conclusion.
The Structural Recreation
According to their report, the board had a long list of possible hypotheses about the fate of MH17: At the start of the investigation, they weren't ruling out pilot error, a weather event, or even space debris.
To make things even more difficult, the plane fell out of the sky at 33,000 feet (10,000 metres) and broke up in the air, meaning it would be difficult to figure out which fragments were caused by impact with the ground versus a foreign object. Over the course of the last year, they built a steel framework that exactly replicated the size and shape of a Boeing 777-200ER.
There, in a hangar at a Dutch airbase, they attached every piece of the plane's body recovered from the crash site, slowly and painstakingly reconstructing the plane's shell itself:
The Chemical Forensics
As the reconstruction took shape, they began to find a pattern of puncture holes and ricochet marks of similar size, especially over the forward left side of the fuselage -- as if a warhead and exploded nearby and sent pieces of shrapnel into the front end of the plane and cockpit.
In fact, investigators also began recovering pieces of metal shaped like cubes and bowties, which could be identified as the standardised metal shrapnel packed inside Buk missile warheads. The investigators call them "high-energy objects," describing how the pattern of impact across the fuselage helped them determine the speed and type of detonation thanks to "stringing," where the direction of an object is traced using a piece of plastic or string.
These metal pieces, which were recovered throughout the cockpit pieces, fuselage, and the bodies of the crew in the cockpit, were chemically analysed at the Netherlands Forensic Institute. Scientists there found that the tiny metal shards had paint and glass residue on them that matched the plane -- so they could assume they penetrated the fuselage from outside the plane. Another chemical marker? Traces of paint found in the wreckage, that matched that on missile pieces on the crash site.
One thing the investigators couldn't do was chemically match this debris with the Buk system: The report explains that though they tried to get a sample of another warhead for comparison, they weren't able to get the material they needed for analysis -- though they don't explain why.
The Soundwave Analysis
So a hypothesis took shape: The Buk warhead detonated near and above the plane's cockpit. The instantaneous nature of the strike meant there was no audio evidence to go on -- except for what investigators describe as a "sound peak" too high and loud for human ears right before impact.
This sound peak played a surprisingly important role. Because there were multiple recorders in the cockpit, they could determine what direction the super-loud noise was coming from -- which helped them figure out, through triangulation, that the blast took place on the upper left hand side of the fuselage. Weeks of computer analysis came next, integrating all the known impact points of the high-energy objects and the possible trajectories of the missile.
Over time, the combination of chemical and structural analysis, combined with radar and sound wave data, turned the hypothesis into a certainty: "No scenario other than a Buk surface-to-air missile can explain this combination of facts," the investigators write. What still remains unclear, and may remain so forever? Whether that warhead was shot from a pro-Russian missile or a Ukraine one.