On December 5 1872, the British ship Dei Gratia was about 644 kilometers (400 miles) east of the Azores when they came across the Mary Celeste, dreaming aimlessly and completely un-crewed. 

The commander of Dei Gratia – David Morehouse – knew that the ship had set sail for Italy eight days before him, and should have already arrived. He diverted course in order to help and sent his crew aboard. What they found deepened the mystery. The ship had been abandoned, but the crew's belongings remained on board. The ship had at least a six-month supply of food and water and 1,701 gallons of industrial alcohol aboard, but the crew had seemingly abandoned ship, taking the lifeboat and risking the open seas rather than remaining on board.

The few clues available, and the fact that the crew did not later show up, turned the Mary Celeste into an enduring mystery rife for speculation. Explanations range from foul play to natural phenomena, with a few massive sea monsters thrown in for good measure. 

There are suggestions that Morehouse's crew could have attacked the ship themselves, though this does not account for how the slower ship caught up on the faster ship after an eight-day head start. A plausible theory – given that one of the ship's two pumps was disassembled, and a small amount of water was found in the ship's bottom – is that with one pump down, the captain may not have known how much water they were taking on board. When they hit bad weather later, this could have caused the captain to order his crew to abandon ship, rather than risk it sinking.

However, there is one other explanation that gained a boost from a test on a replica hold in order to explain the sinking. The theory goes that some of the alcohol exploded, causing the captain to panic and give the order to board the lifeboat. It seems simple, but the problem is that there were no signs of fire or explosion on the ship when it was found.

Dr Andrea Sella from the University College London Chemistry Department tested the idea, using butane gas and cubes of paper to simulate wooden barrels.

"What we created was a pressure-wave type of explosion," Dr Sella said in a press release. "There was a spectacular wave of flame but, behind it, was relatively cool air. No soot was left behind and there was no burning or scorching."

"Given all the facts we have, this replicates conditions on board the Mary Celeste. The explosion would have been enough to blow open the hatches and would have been completely terrifying for everyone on board."

According to this theory, the explosion could have freaked the captain out enough to give the order to abandon ship, and account for the lack of evidence of explosion or fire.

"It is the most compelling explanation," said Dr Sella. "Of all those suggested, it fits the facts best and explains why they were so keen to get off the ship."