Sinking of the ROKS Cheonan - North Korean Aggression or Friendly Fire?

The recent tension on the Korean peninsula, beginning last March, stems from the sinking of a South Korean Pohang class corvette, the ROKS Cheonan. On Friday, 26 March 2010, an explosion was reported to have occurred near the Cheonan, near the stern of the ship at 9:22 p.m. local time. The ship, which broke in half off of Baengnyeong Island in South Korean waters, had previously participated in a large anti-submarine warfare training exercise 8 days previously. 40 South Korean sailors were confirmed dead, and 6 missing. Rough waters caused the poorly executed rescue operation to cost more lives when a Cambodian freighter collided with a privately owned vessel participating in the rescue. Immediate South Korean response to the sinking of the ship stressed that there was no indication of North Korean involvement.

Although initial reports played down the possibility of North Korean involvement, as the days passed, South Korean "leaks" indicated that a North Korean miniature submarine could have launched a torpedo into the Cheonan. Pro-Government newspapers began publishing reports of North Korean involvement, indicating a torpedo had hit the Cheonan, causing it to split in half. Parts of an intact torpedo were shown as evidence, complete with North Korean markings and production numbers.

This is a picture of the North Korean torpedo that supposedly hit the Cheonan. The problem with this, however, is that a torpedo like the one supposedly launched at the Cheonan, would be traveling 40-50 knots, and would leave no distinguishable remains like the propeller. South Korean and American investigations "confirmed" North Korean involvement with its own investigation. Independent investigations, as well as Chinese reports, pointed towards a floating mine. Russian investigations reportedly agreed. The argument for a friendly fire incident can be attributed to the NATO-grade explosive residue found on the Cheonan. North Korean torpedoes would not be using NATO weaponry. The sinking was also well within South Korean waters, and close to a large anti-submarine base, which would have easily detected the poorly made North Korean submarines.

I personally doubt that the North Koreans were involved, but I'd like to know your opinions!