Claims about extraterrestrial life are once again making headlines. Unlike a December incident involving an assertion about the discovery of arsenic-eating microbes in Mono Lake, however, journalists have treated the latest news with intense skepticism almost from the outset.

On Friday, the Journal of Cosmology published research by NASA scientist Richard Hoover reporting that he had found fossils resembling bacteria on Earth in a class of rare meteorites. Hoover tested the filament-shaped structures for nitrogen, which is essential to life on this planet, and found none, leading him to conclude that they “represent the remains of extraterrestrial life forms that grew on the parent bodies of meteorites when liquid water was present, long before the meteorites entered the Earth’s atmosphere.”

Unsurprisingly, the research caused a lot of media commotion. Nature’s Great Beyond blog correctly observed that headlines along the lines of “Extraterrestrials found at last!” have been conspicuously absent, however.

The most boosterish reporting came from the outlet to which Hoover gave an exclusive: Fox News (a choice that made other scientists suspicious from the start). There are a few lines in the middle of the story, published Saturday, about the need to remain circumspect, but the more potent message is that the research is “groundbreaking,” “shocking,” “profound, very important and extraordinary.” The article also quotes an editor’s note from the Journal of Cosmology, which claimed, “No other paper in the history of science has undergone such a thorough analysis, and no other scientific journal in the history of science has made such a profoundly important paper available to the scientific community, for comment, before it is published.”

The Knight Science Journalism Tracker’s Charlie Petit pointed out, “That kind of hyperbolic gumption alone ought to set most reporter’s smell-a-rat instincts to high alert.” And whether it was the editor’s note or the memory of other astrobiology stories gone wrong, on high alert they were.

In December, a NASA press release that promised to reveal “an astrobiology finding that will impact the search for evidence of extraterrestrial life” at an upcoming meeting ended up spreading widespread confusion when bloggers and a few national media outlets inferred that an announcement about the discovery of aliens was imminent. It turned out the discovery involved microbes that could swap phosphorous, thought to be essential for life, with arsenic, which is highly toxic in basic metabolic processes and in its DNA. The research was still interesting, but after an early round of heavy, uncritical coverage, a number of scientists started criticizing its methods and conclusions. It was an absolute circus, but there are older and even more direct antecedents to the microbes-in-meteors story.

In a couple of the earliest blog posts about Hoover’s research in the Journal of Cosmology, Discover’s Phil Plait and’s Alan Boyle both recalled an incident in 1996 when NASA scientists presented photos of worm-like structures resembling bacteria that they’d found in a meteorite from Mars (Time also featured a good account of the research and the related theory of panspermia). The research has still not been verified.

“The initial evidence was the subject of dramatic news conferences and huge headlines, but as time went on, doubts about the findings grew,” Boyle wrote. “Today, few astrobiologists see the Mars meteorite as containing any conclusive evidence for the existence of past or present Martian life.” (The end of his post features a useful list of links to coverage of other controversies in astrobiology.)

The concern about Hoover’s meteorites, Plait and Boyle explained, is that they’ve been around a while (one fell in France in 1864), so it’s possible that the microscopic filaments resembling bacteria are actually earthly contamination. Boyle soon added updates to his post from scientists questioning Hoover’s methods and conclusions (and Plait would write a follow-up post on Monday expressing his personal opinion, after more experts had weighed in, that Hoover was wrong). Skepticism was simmering far and wide.

“Why isn’t the news plastered across the front page of NASA’s website?” Discovery News’s Ian O’Neill wisely asked on Saturday evening. He wouldn’t have his answer until Monday afternoon, when the agency released a statement saying it could not “stand behind or support a scientific claim unless it has been peer-reviewed or thoroughly examined by other qualified experts. This paper was submitted in 2007 to the International Journal of Astrobiology. However, the peer review process was not completed for that submission. NASA also was unaware of the recent submission of the paper to the Journal of Cosmology or of the paper’s subsequent publication. Additional questions should be directed to the author of the paper.”

Curtis Brainard writes on science and environment reporting. Follow him on Twitter @cbrainard.