As the investigation into the Boston Marathon bombing entered its third day, forensic specialists with the FBI, the ATF, and local law enforcement continued to review countless amounts photo and video evidence. And while officials asked citizens to help find the suspect and Internet gurus helped make sense of the "bag or backpack" holding the explosives, important details have emerged from the "ends of the Earth" effort to understand the bombs themselves. At a press briefing early Tuesday evening, FBI special agent in charge of the investigation Richard DesLauriers said analysts at headquarters in Quantico were examining black nylon that could be from a backpack, which appeared to contain BB parts and nails, "possibly" in a pressure cooker device. Later Tuesday evening, the FBI released two photos — a scrap of black nylon and a hunk of metal — and by Wednesday morning more images had emerged: pictures of the debris from the explosions taken by investigators that combined to become, well, bomb parts. (Updates from our live blog: A pressure cooker lid has reportedly been obtained, and White House Press Secretary Jay Carney said at a briefing that he wouldn't characterize the president's feelings on the speed of the investigation. CNN reported there had been "substantial progress" in the investigation.) The FBI will try to reconstruct the bomb for answers, and the next briefing is scheduled for early Wednesday afternoon, but as the investigation moves from its "infant" stages to immediate forensics analysis that could lead to answers, the bomb parts and the crime scene itself provide an early public assessment for this crowdsourced investigation. (Update: Authorities appeared to have a suspect — follow here.)
The Color of Smoke: High or Low Explosives
One of the biggest early indicators in the investigation comes from photos: the color and density of the smoke may be indicative of a certain type of bomb. Dr. Adam B. Hall, a forensic chemist, told The New Yorker's Paige Williams that the very white color in photos would indicate a "high" explosive such as an ANFO (ammonium nitrate, or fertilizer, plus fuel oil) or T.A.T.P (triacetone triperoxide, a mixture of commercially available acetone, hydrogen peroxide, and something acidic, like vinegar). Michael Marks, a Naval Criminal Investigative Service retiree, says investigators should be analyzing multiple colors, he told Wired's Danger Room. "I'm seeing both dirty grey and white," he said. To him, dirty grey would suggest a high explosive, whereas "bright white" would suggest gunpowder, which sources tell ABC News was used in at least one bomb. (Reuters reported both gunpowder and schrapnel were used.) However, one law enforcement official described the bombs as a "low explosive" to CBS News. Of course, it's possible that the two bombs were made from different materials. But both of these experts concede that they're too far away from the scene to really know. The crowdsourced photos pouring out of the Internet — like this giant spreadsheet of Flickr photos geotagged at the location and video clips at the scene — as well as eyewitness accounts could bring more clarity. Already one group claims to have found a photo of pressure cooker lid on the roof of a building — the AP reports it's been recovered by authorities — and 4chan and Reddit are on the case with the photos.