A professor on Monday backed one piece of key evidence cited by an investigation team as proof that North Korea was responsible for the deadly sinking of a South Korean warship as opponents
continued to raise doubts about the probe results.
A South Korean-led multinational team concluded in May that a North Korean torpedo sank the Cheonan warship in March, citing "overwhelming
evidence" that includes a torpedo fragment marked with "No. 1" in Korean that was retrieved from the site of the sinking.
Investigators said the marking, written in North Korean style, proved that the torpedo came from the North.
Skeptics have cast doubts about the evidence, arguing that the writing in blue ink inside the propulsion part of the torpedo would have melted fromthe intense heat of the explosion.
Song Tae-ho, professor of mechanical engineering at the Korea Advanced Institute of Science and Technology, rebutted claims that the ink used for the handwritten mark would have burned off because the heat of the explosion
apparently cooled rapidly underwater.
"Under any extreme circumstances, the temperature at the propulsion part would have risen up to 20 degrees Celsius at most," Song told reporters at a press conference at the Ministry of National Defense.
"So there is no possibility that the handwritten mark could have been damaged by the heat of the blast," said Song, an expert in heat transfer, citing the results of his own experiments.
Emphasizing that he worked independently, Song said his press conference wasn't commissioned by the defense ministry, and that he decided to hold it to dispel persistent skepticism over the results of the multinational investigation.
Last month, two South Korean-born U.S. scientists, including Lee Seung-hun, a physics professor at the University of Virginia, held a press conference in Tokyo and raised doubts over the handwritten mark.
Song said the argument by the U.S.-based scientists was probably based on "incorrect factors" in their experiment that "ignored a basic theory of heat transfer."
The investigation team cited a so-called "bubble jet effect," a powerful water pillar created when a torpedo explodes, as the cause that split the Cheonan in two, killing 46 sailors.
Song claimed that the temperature on the surface of the propulsion part at the time of the blast was believed to rise up to 604 C, but cool down to 28 C within 0.1 second of the explosion.
"Let me assume that fire is set on one side of a piece of plasterboard.
Within such a short period of time, the heat won't be transferred to the other side of the board," Song said.
"Because the handwritten mark was put inside the propulsion part, I think the heat of the explosion didn't damage it," the professor said.