BEIJING — The chief scientist of China’s lunar probe program has been forced to defend the authenticity of its first published photograph after Internet moongazers suggested it might be a copy.

Prime Minister Wen of China unveiled the first photograph sent back from the inaugural mission of the Chang’e-1 lunar probe amid much patriotic emotion last week.

But in a response to public skepticism unusual for such a token of national pride, Internet bulletin boards began pointing out the similarity of the photograph to one published by NASA, the American space agency, two years ago.

Yesterday, the senior scientist of the China Lunar Exploration Project, Ouyang Ziyuan, insisted that the photograph had not been copied and really was genuine.

“China’s first moon photo is absolutely not a fake,” he said, adding that though the two shots were of the same part of the moon’s surface, a new crater was shown in the Chinese version.

Chang’e-1, named after a fairy who fled to the moon from an unhappy marriage, was launched in October to much fanfare. It represents the start of the second phase, after manned space flight, of China’s long-term goal of putting a man on the moon by 2020.

When the first photograph, a compilation of 19 individual shots, was unveiled to the public, Mr. Wen was described by state press as “passionate,” an unusual descriptor for a Chinese Communist Party leader.

“Chinese people’s dream of flying to the moon for more than 1,000 years has started to materialize,” he said.

But one bulletin board poster, who called himself IMCC, wondered if it was a coincidence that the picture was so similar to the NASA version.

“The two pictures are not just alike,” he wrote. “They are actually the same. If this is indeed a fake, I feel truly sorry. How can such a big country try to fool the public?”

The suggestion might be regarded as another coming-of-age ritual for the fast-developing China, like the space program itself. After all, the allegation that Neil Armstrong’s moon landing in 1969 was faked by NASA is a longtime conspiracy theory.

However, it comes at a time when China’s 160 million Internet surfers scent blood. The biggest dispute of recent weeks has been about whether a photograph allegedly of a South China tiger in a forest, which would have been the first sighting for years of an animal now thought only to survive in zoos, was real. The photograph was widely publicized and welcomed by government wildlife officials.

An official inquiry yesterday pronounced it fake — two weeks after an Internet hunt that eventually found a calendar shot of a tiger identical to the one apparently photographed in the forest. “When the tiger was eventually shown to be a fake, the whole world laughed,” IMCC went on. “Maybe this is the same.”

Not everyone agreed. One pointed out that since NASA had photographed the entire surface of the moon, a Chinese version could only be a fake if it didn’t have a perfect match in the American set.

Examination of the two lunar photographs does suggest that they were of the same section of the moon — a highland area located between 54 to 70 degrees south latitude and 57 to 83 degrees east longitude.

But an extra hole does seem to be visible in the Chinese version, which Mr. Ouyang attributed to the possibility that the surface had been struck by a meteorite or other celestial body in the last two years.

Or, he added, the Chinese photograph might just be of better quality than the American.