A bacterium trained to substitute arsenic for phosphorus—one of six elements considered essential for life—in some of its basic cellular functions is stirring widespread, high profile coverage.

On Monday, a cryptic NASA press release about the research—embargoed by the journal Science until Thursday afternoon—led to wild speculation about the discovery of life beyond Earth. What the new finding actually suggests, as a well done Nature News article put it, is “the possibility of a biochemistry very different from the one we know, which could be used by organisms in post or present extreme environments on Earth, or even on other planets.”

The arsenic-munching microbe has quickly grown into a major media story. In a column criticizing the “aliens” speculation that was posted Wednesday, while the Science paper was still under embargo, I cautioned that it was an “interesting piece of research, but certainly not one that is bound to make the front page, or perhaps any page.” Allow me to eat my words. The New York Times, The Washington Post, and the San Francisco Chronicle all fronted the news. The Wall Street Journal put it on page three and USA Today on page four.

In retrospect, the high-profile coverage is deserved. Scientists have long believed that all life needs hydrogen, oxygen, carbon, nitrogen, sulfur, and phosphorous to survive, and the discovery of a microbe that can eat arsenic and incorporate it into its cellular structure could upend that basic understanding of nature. Unfortunately, a lot of the coverage has still been faulty and overblown.

A prime example was a Gizmodo story posted Thursday on the usually dependable Wired Science blog. “Hours before its special news conference today, the cat is out of the bag,” the lede read. “NASA has discovered a completely new life form that doesn’t share the biological building blocks of anything currently living on planet Earth. This changes everything.”

In fact, the bacterium that was coaxed into the arsenic-phosphorous substitution was collected from Mono Lake in California and shares all the same building blocks as other life. The faulty Gizmodo article aroused the ire of science journalist David Dobbs, who runs the blog Neuron Culture at Wired Science. In an effort to push it farther down on the website’s home page, Dobbs penned a post highlighting examples of more accurate coverage.

“Hoping to bury Gazmodo [sic] story on Lake Mono bugs, I wrote http://bit.ly/ddNoAliens. Alas, our blogs don’t auto-push WiSci news down. #nicetry,” he explained in a tweet.

In his post, Dobbs quotes an excellent analysis by journalist Ed Yong, who runs the Discover blog, Not Exactly Rocket Science:

The discovery is amazing, but it’s easy to go overboard with it. For example, this breathlessly hyperbolic piece, published last year, suggests that finding such bacteria would be “one of the most significant scientific discoveries of all time”. It would imply that “Mono Lake was home to a form of life biologically distinct from all other known life on Earth” and “strongly suggest that life got started on our planet not once, but at least twice”.

The results do nothing of the sort. For a start, the bacteria - a strain known as GFAJ-1 - don’t depend on arsenic. They still contain detectable levels of phosphorus in their molecules and they actually grow better on phosphorus if given the chance. It’s just that they might be able to do without this typically essential element - an extreme and impressive ability in itself.

Nor do the bacteria belong to a second branch of life on Earth - the so-called “shadow biosphere” that Wolfe-Simon talked about a year ago. When she studied the genes of these arsenic-lovers, she found that they belong to a group called the Oceanospirillales. They are no stranger to difficult diets. Bacteria from the same order are munching away at the oil that was spilled into the Gulf of Mexico earlier this year. The arsenic-based bacteria aren’t a parallel branch of life; they’re very much part of the same tree that the rest of us belong too.

That doesn’t, however, make them any less extraordinary.

Thankfully, Wired Science did end pushing down the Gizmodo piece with a much better article from Science News (featuring the superb lede, “When cooking up the stuff of life, you can’t just substitute margarine for butter. Or so scientists thought”). Oddly enough, though, the website of Wired in the United Kingdom (a separate edition) also coughed up a highly misleading story under the erroneous headline “NASA discovers second form of life.” The second paragraph even draws an irresponsible connection between the Science paper and recent news about Earth-like exoplanets:

[The research] suggests that they’ve developed entirely independently from our life, implying that if life has evolved twice on Earth, then it’s far more likely to have evolved off Earth too — especially as it’s believed by astronomers that among stars similar to the Sun, as many as one in four could have small rocky planets like Earth, at least some of which would occupy the same “goldilocks zone” that Earth exists in — neither too hot, nor too cold, for life to emerge.

Such extrapolation should be avoided in science reporting. Fortunately, all of the big U.S. newspapers that covered the story were careful to explain the microbe from Mono Lake belongs to the same “tree of life” from which sprang all other earthly critters, from human beings to the chemosynthetic extremeophiles living near deep-sea ocean vents. The Washington Post did, however, change overwrought headline, “Second Genesis on Earth?” to the somewhat more responsible, “Bacteria stir debate about ‘shadow biosphere.’”

And the The New York Times got a little hyperbolic in its lede, which reported that the new research “open[s] up the possibility that organisms could exist elsewhere in the universe or even here on Earth using biochemical power we have not yet dared to dream about.”

The research does open that possibility, but, in fact, a few scientists have been dreaming about it for some time now. As the Washington Post article pointed out, theoretical physicist and cosmologist Paul Davies, one of the co-authors of this week’s paper, has “been thinking about the idea of a shadow biosphere for a decade and had written a paper on it in 2005.” And an interesting piece in The Christian Science Monitor reported that “a small number of scientists have been pushing the idea of ‘life as we don’t know it’” for at least half a decade.

Any discussion of the “shadow biosphere” or “life as we don’t know it” should make it clear, however, that scientists’ success in inducing the Mono Lake bacterium to substitute arsenic for phosphorus does not prove that researchers have yet discovered a fundamentally different basis for life… or aliens.

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Curtis Brainard is the editor of The Observatory, CJR's online critique of science and environment reporting. Follow him on Twitter @cbrainard.