paris attacks police officer reuters RTS6ZSC Reuters

While the world mourns those who died in the November 13 Paris attacks, investigators are hard at work piecing together the terrorist plot that has killed at least 129 people and seriously injured 99 others.

One question Parisian authorities have answered, however, is what explosives the attackers set off during the attacks.

Paris prosecutor Francois Molins told reporters on November 14 that seven of eight attackers set off shrapnel-packed bomb vests designed for causing the "maximum number of casualties while committing suicide."

The key ingredient in the bombs, Molins said, was a compound called triacetone triperoxide, or TATP — a crystalline powder that is a nightmare to terrorists as well as authorities.

An unstable white powder

acetone peroxide triacetone triperoxide Public domain

TATP is easy to make and hard to detect, but is also incredibly unstable. In fact, all it takes is a firm tap to explode TATP with a force that's about 80% as strong as TNT. (Which is why it has gained an infamous reputation as "the Mother of Satan" among terrorists who make it, according to The Future of Things.)

The infamous "shoe bomber" used TATP in 2001, as did terrorists in London in 2005 and 2006. The chemical was also in bombs detonated at the University of Oklahoma in 2005 and Texas City in 2006, according to explosives researchers at Northeastern University.

"TATP and other explosives of the peroxide family are used extensively by terrorist organizations around the world because they are easy to prepare and very difficult to detect," Ehud Keinan, a chemist at the Technion-Israel Institute of Technology, said in a 2005 press release about his research of the chemical.

You might recognize two chemicals in TATP's full name — triacetone triperoxide — because they're ingredients you can find in your local pharmacy's cosmetics and first aid isles.

"TATP can be easily prepared in a basement lab using commercially available starting materials," according to GlobalSecurity.org, which also notes "it's easy to blow yourself up when you make it."

Jimmie Oxley, an explosives researcher at the University of Rhode Island, told Tech Insider by email that making TATP is as easy as "baking a cake."

"We have done a lot of work trying to prevent its synthesis," wrote Oxley, who has experimented with adding trace chemicals to hydrogen peroxide in hopes of foiling TATP's homemade production. "It isn't easy to do and the ingredients are very common."

Chemistry of a nightmare

One reason TATP is difficult to detect is because it does not contain nitrogen, a key component of homemade "fertilizer" bombs that security scanners are now very good at finding.

Each molecule contains only hydrogen, oxygen, and carbon some of the most common elements on Earth — shaped in a ring.

Acetone peroxide triacetone triperoxide TATP A chemical model of triacetone triperoxide (TATP). It's made of oxygen (red), carbon (black), and hydrogen (white). Public domain

The explosive power of TATP has puzzled scientists since its discovery in 1895. Unlike nitrogen-based bomb materials, which store up energy as they're cooked into explosive form, TATP can be made at room temperature — no flames required.

So where does it get its explosive energy, if not by heating?

It wasn't until 2005 that Keinan figured out detonating TATP is more like a massive air blast than a fire bomb. When a crystal of the explosive is rattled hard enough, each solid molecule instantly breaks into four gas molecules.

"Although the gas is at room temperature, it has the same density as the solid, and four times as many molecules, so it has 200 times the pressure of the surrounding air," according to the release about Keinan and his colleagues' 2005 study of TATP.

"This enormous pressure — one-[and-a-half] tons per square inch — then pushes outward, creating an explosive force" on par with TNT, states the release.

"In a TATP explosion, the gas molecules give up their energy of motion to the surroundings, in the process creating the shock wave that does the damage."

Can we detect it?

Scientists are now working feverishly to create practical ways to find TATP before it can be used to kill innocent people.

ACRO Security Technologies, a company founded by Keinan, has created a disposable marker-size "peroxide explosives tester," or ACRO-P.E.T.

"The ACRO-P.E.T. provides an immediate answer to whether a suspicious material that has been discovered somewhere ... contains even minute quantities of a peroxide-based explosive," Keinan told The Future of Things.

Other researchers are working on ways to find TATP when it's being transported, and without the need for a direct chemical test like Keinan's device.

In 2011, for example, scientists at Hitachi in Japan created a machine that sucks in air from around a passenger and — in two seconds — can sniff out minute traces of TATP.

A German research group also announced this summer that large amounts of TATP can be detected in transit. Because the chemical is so touchy, they say in their study, it's usually dissolved in a special liquid before being moved around — and that fluid's unique odor is what they hope security scanners of the future could sniff out.

Warning: We have purposefully ommitted key details about TATP's manufacture. Do not attempt to make it or any other explosive, for that matter.

Update: We misstated the strength of TATP and have corrected the error.