A meteorite that lit the sky over Sri Lanka with a yellow and green flame when it fell to earth on Dec. 29, 2012, contains "fossilized biological structures," according to researchers in Britain, Sri Lanka, and the United States. Elaborating on claims they first made in January, the scientists are also seeking to answer critics who are skeptical of their findings.
The team, led by Jamie Wallis of Cardiff University and Chandra Wickramasinghe, director of the Buckingham Center for Astrobiology, says that electron microscope images depict what look to be microscopic diatoms, a form of algae, along with other structures in fragments of the meteorite.
Such a finding would bolster the theory of "panspermia," which Wickramasinghe helped develop, and which posits that asteroids and other bodies spread tiny tidbits of life as they travel through space.
The study released Monday is based on a sample that was gathered by police and examined by the Medical Research Institute of the Ministry of Health in Colombo. Scientists say they later obtained 628 other samples, of which only three were found to be possible meteorite fragments.
The researchers say they analyzed the stones with a scanning electron microscope at Cardiff University, which "resulted in a number of images showing diatom frustules, some of which were clearly embedded in the rock matrix, thereby excluding the possibility of post-arrival contamination." Frustules, we should note, are the silica-based shells of diatoms.
The new study expands on a paper published in January, which reported "the discovery for the first time of diatom frustules in a carbonaceous meteorite" that fell near the historic city of Polonnaruwa.
That initial bulletin was criticized for its lack of detail on how the samples were recovered, with many observers concluding that the samples had been contaminated by water in the rice paddies that dot the region. And some have questioned whether a meteorite actually fell near Polonnaruwa. It is not registered, for instance, at the Meteoritical Society's site.
But that has not deterred the study's leaders from saying their work may represent one of the biggest scientific breakthroughs in hundreds of years. And they say the samples' extremely low levels of nitrogen provide further proof that they have found ancient fossils.
"I think the discovery of an unequivocal microbial structure such as a diatom, deeply trapped in the rock matrix, proves beyond doubt that this life existed in the parent comet from which the meteorite was derived," Wickramasinghe told Sri Lanka's The Island news site in January. "The highly intricate and woven patterns on the outer shells of diatoms are impossible to generate by any other process than biology.... The cosmic ancestry of humans becomes ever more securely established."
Technology Review, which notes that the new study must be peer-reviewed — and samples must be shared with other scientists — before its theories can be considered, also notes a couple of alternate explanations:
"One is that the fireball was of terrestrial origin, a remnant of one of the many asteroid impacts in Earth's history that that have ejected billions of tonnes of rock and water into space, presumably with biological material inside. Another is that the structures are not biological and have a different explanation."
After the January study was published, astonomer Phil Plait wrote a detailed and deeply skeptical review of the findings for Slate. In short, he said the researchers were wrong — or, as he put it, "meteorwrong."
Plait consulted evolutionary biology professor Patrick Kociolek of the University of Colorado at Boulder, who found that "the 'source' of the diatoms from outer space, must have gone through the same evolutionary events as here on earth." The sample, Kociolek said, was clearly contaminated.
This afternoon, Plait offered an analysis of the new study, in which he remains unconvinced of its merits.
Both of the studies by Wallis, Wickramasinghe, and their colleagues were published in ,which has previously been moved to defend its articles, including a 2011 paper that stated "structures in rare meteorites appear to be microscopic fossils of extraterrestrial beings that resemble algae known as cyanobacteria," as The Guardian reported.
The skeptical response to that article, The Journal of Cosmology's editors wrote, caused them to reminisce about "totalitarian states and theocracies, where defenders of the faith, and Grand Inquisitors, armed with their Bibles, threatened, tortured, and killed those who challenged prevailing dogma." The Journal'seditorial statement was posted by David Dobbs for the Neuron Culture blog at Wired.
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