"The fact is, we dont know what happened," said Sam Thurman, who served as the Mars Polar Lander mission operations director.

The Polar Lander was last heard from minutes before it entered the martian atmosphere on December 3. The craft was not designed to send back data during its final descent, and no signals were received after the scheduled time of touchdown.

Recent news reports have asserted that the review board, whose findings will be released in mid-March, had identified a "smoking gun" in the landers demise.

The culprit was said to be a so-called contact switch that was designed to signal when one of the spacecrafts three landing legs touched the martian surface.

The switch, in turn, would signal the computer to turn off the crafts descent engines.

According to the recent speculation, the switch was accidentally triggered long before touchdown by the deployment of the landing legs, resulting in a premature shutdown of the engines and destruction of the lander.

Thurman, however, denied that a culprit had been identified. Speaking to SPACE.com, he said, "Theres far, far less than a smoking gun there."

Polar Lander project manager Richard Cook agreed that the contact switch was just one of many possible culprits being studied by the review board. "They tried to figure out every single thing it could possibly be, and [the contact switch] is on the list."

According to Cook, reviewers are evaluating "pretty much every component they could think of" at Lockheed Martin in Denver, where the Polar Lander was built.

"Theyre still doing testing in Denver," Cook said. "Theres nothing definitive. The next couple of weeks should tell."

To Thurman, the Polar Landers failure is reminiscent of the disappearance of the Mars Observer probe in 1993. That spacecraft ceased transmitting shortly before it was expected to go into orbit around Mars. A review panel identified an on-board explosion as the probable cause, but in the absence of hard data, the conclusion was considered speculative at best.

"This is Mars Observer all over again," Thurman told SPACE.com. "We cant say for sure this was [the culprit] as opposed to any of the other things that might possibly have gone wrong."

"Since we dont have any data from [the spacecrafts] entry, descent and landing, well never know for sure," Thurman said.

Nevertheless, he added, the review board is under some pressure to identify a particular cause.

"Theyre almost obligated to give their best assessment of what the most likely cause of the failure might be, or at least the relative possibility," Thurman said. "Because thats what they were asked to do to try to understand what might have gone wrong, and to help the [Mars] program decide how to do better next time."

But owing to the lack of data, Thurman stressed, "Its very difficult to assign likelihood. We have no concrete information about what really happened."

If a specific cause is identified in the report next month, Thuman said, "Im hoping to urge a cautionary note in the interpretation of it. Thats an assessment that cant be confirmed by any real data, and I think everybody needs to remember that."