If the claim is confirmed it will provide evidence in support of the theory of cometary panspermia
first proposed by the late English astronomer Fred Hoyle
and Chandra Wickramasinghe
. The theory claims that life on Earth began when a meteorite bearing simple life forms impacted with the Earth billions of year of ago. According to the theory of panspermia life is widespread throughout the entire universe and it is distributed across the vast stretches of space by meteoroids and asteroids.
Wickramasinghe is a member of the Cardiff team that carried out the latest analysis.
According to MIT Technology Review
, on 29 December 2012, a fireball streaked across the sky over the Sri Lankan province of Polonnaruwa and landed on Earth. Local police authorities collected fragments of the meteorite from several spots in the countryside and sent them to the Sri Lankan Medical Research Institute of the Ministry of Health in Colombo.
Sri Lankan geologists arranged for samples of the fragments to be sent to scientists in Cardiff University for further studies after they detected "curious features" on the stones.
Initial microscopic analysis in December by Chandra Wickramasinghe of the Buckingham Center for Astrobiology at the University of Buckingham in the UK claimed that the stones contained "siliceous microalgae known as diatoms," a type of microscopic algae.
In a paper titled "Fossil Diatoms In A New Carbonaceous Meteorite" (PDF)
) published in the controversial Journal of Cosmology
, Wickramasinghe claimed to have found "a microstructure and morphology characteristic of a wide class of terrestrial diatoms." He went on to assert that "the presence of structures of this kind in any extraterrestrial setting could be construed as unequivocal proof of biology."
The claim that the presence of supposedly biological "microstructures" in the meteorite was evidence of life of extraterrestrial origin was greeted with widespread skepticism and even derision.
But according to MIT Technology Review
, a team of of researchers at Cardiff University have released in March 2013 the results of further study of the meteorite fragments. The team claims that structures embedded in the fragments are definitely "fossilized biological structures."
According to a paper titled: "The Polonnaruwa Meteorite: Oxygen isotope, Crystalline and Biological Composition,"
the Cardiff team claimed that the Polonnaruwa meteorites contain fossilized biological structures fused into the rock matrix. The researchers said that tests which included X-Ray Diffraction (XRD) analysis, Triple Oxygen Isotope analysis and Scanning Electron Microscopic (SEM) studies have ruled out the possibility of terrestrial contamination of the meteorite fragments.
According to MIT Technology Review
, the study authors, Jamie Wallis et al.
, reported that they received a total 628 meteorite fragments that were collected from rice fields in the Sri Lankan region of Polonnaruwa. The authors said they were able to confirm that three of the stones were meteorite fragments.
The confirmation was based on measurements of their densities and the fact that they showed features such as a partially fused crust indicating heating due to friction as the meteor entered the earth's atmosphere.
The stones were found to have a carbon content of up to 4 per cent. They were also found to be rich in organic compounds. The researchers concluded that the meteor was probably a small comet.
According to the authors
, electron microscope images of the structure embedded in one of the stones (see images below
) show a complex, thick-walled, carbon-rich microfossil about 100 micrometres across. The structures, according to the authors, are similar to a group of mostly extinct marine diinoflagellate algae.
One of the images, according to the astrobiologists, show well-preserved flagella that are two micrometers in diameter and 100 micrometers long.
Wallis and colleagues pointed out that the flagella are unusually long and may be evidence that the algae evolved in a low-gravity and low-pressure environment.
The research team measured the relative abundance of various elements in the samples and found low levels of nitrogen. The authors explained that low nitrogen levels rule out the possibility of contamination by modern organisms on Earth which have relatively high nitrogen content. The authors also said the fact that the samples were embedded deep within the rock matrix was evidence that they were not the result of contamination after they entered the Earth's atmosphere.
According to the astrobiologists
The existence of numerous nitrogen depleted highly carbonaceous fossilized biological structures fused into the rock matrix is inconsistent with recent terrestrial contamination. Oxygen isotope results compare well with those of CI and CI-like chondrites but are inconsistent with the fulgurite hypothesis.
MIT Technology Review
reports Wallis and his colleagues said they were convinced that the body of evidence is conclusive. The authors said: "This provides clear and convincing evidence that these obviously ancient remains of extinct marine algae found embedded in the Polonnaruwa meteorite are indigenous to the stones and not the result of post-arrival microbial contaminants."
As expected, these startling claims have generated controversy and refutations. While Wallis and his co-workers believe that "the presence of fossilized biological structures provides compelling evidence in support of the theory of cometary panspermia first proposed over thirty years ago," some critics have said the stones could have been formed by lightning strikes on Earth. Wallis and his colleagues responded, saying that there was no evidence of lightning activity at the time the meteorite crashed and that the stones do not show any features characteristic of those formed by a lightning strike. The authors also pointed out that temperatures typically generated by lightning strikes would have destroyed the biological content of the meteorite pieces.
Other critics say it is possible that the meteorites are of terrestrial origin. According to MIT Technology Review
, some critics said the meteorites could have been derived from "a remnant of one of the many asteroid impacts in Earth’s history that have ejected billions of tonnes of rock and water into space, presumably with biological material inside. Another(theory) is that the structures are not biological and have a different explanation."
As Extreme Tech
notes one of the factors that may count against the credibility of the paper is the fact that it was published in the Journal of Cosmology
, a "peer-reviewed journal" that has come under criticism since it began publishing in 2009. The journal came under fire after it published a paper by NASA engineer Richard Hoover, who claimed he found fossils “similar to cyanobacteria” in a sample of meteorites.
reports that P.Z. Myers, a biologist at the University of Minnesota, Morris, wrote on his science blog Pharyngula
: "It isn't a real science journal at all, but is the ginned-up website of a small group of crank academics obsessed with the idea... that life originated in outer space and simply rained down on Earth."
Wickramasinghe, one of the study authors, is well known as a fervent proponent of panspermia, a theory which he proposed with the late English astronomer Fred Hoyle.
According to Phil Plait, an astronomer writing in Slate
: "Wickramasinghe is fervent proponent of [panspermia]. So much so that he attributes everything to life in space. He's said that the flu comes from space. He's said SARS comes from space. The list goes on and on. Wickramasinghe jumps on everything, with little or no evidence, and says it's from outer space, so I think there's a case to be made for a bias on his part."