A Place to Stand

  I have recently been reading about panspermia, the theory that life originated not on Earth but in space, probably on comets, and will thus have crossed and settled the universe. I am impressed with the balance of evidence. Not convinced, because one should not make up one's mind before there is sufficient evidence, but I would bet on it being more likely than a purely terrestrial origin of life.

    This is by Chandra Wickramasinghe, the most prominent living proponent.:

The radical answer proposed by Fred Hoyle and myself in the late 1970s was that we came from space! Our genes and those of all living forms on Earth were brought here by comets, neatly packaged within cosmic microorganisms. The idea was not plucked out of the skies, but was the result of careful analysis of astronomical and biological data over several years.

we argued the molecular arrangements bearing this information could not arise under the hopelessly diminutive conditions that existed in a “warm little terrestrial pond.” The origin of life must surely involve the combined resources of all the stars in all the galaxies of the Universe. Once originated, however, the dispersal and distribution of life across cosmic distances would be assured by virtue of the well-attested resistance of bacteria to the harshest of conditions in space.

The next fact in our favour was that life appears on early Earth when comets were colliding with great frequency and when the planet had neither a stable ocean or atmosphere.² The conditions on Earth at this time were manifestly unsuitable for producing even the chemical building blocks of life indigenously.

In the late 1970s there was also a growing body of evidence for biochemical substances in the interstellar clouds of deep space.3 Astronomical observations, first made by my brother Professor Dayal Wickramasinghe of the Australian National University and David Allen, showed in 1979 that cosmic dust had a composition similar to dried out bacteria.4 They also showed the same conclusion to hold for the dust that flowed out of Halley’s comet in March 1986.5 The discovery that clinched our hypothesis was the realisation that one third of all the available carbon in interstellar space had to be tied up in the form of hollow organic particles with the average size of a bacterium and with spectral properties that could not be distinguished from biological material. No other process apart from biology seemed reasonable to invoke in order to produce the vast amount (some 1030 tonnes) of bacteria-like matter that existed in our galaxy alone.
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More Evidence

A 2008 analysis of ¹²C/¹³C isotopic ratios of organic compounds found in the Murchison meteorite indicates a non-terrestrial origin for these molecules rather than terrestrial contamination....

On August 8, 2011, a report, based on NASA studies with meteorites  found on Earth was published suggesting building blocks of DNA (adenine, guanine and related organic molecules) may have been formed extraterrestrially in outer space. In October 2011, scientists reported that cosmic dust contains complex organic matter

Of the four Viking biological experiments performed by the Mars lander Viking in 1976, only the LR (Labeled Release) experiment gave results that were initially indicative of life (metabolism)....

Microstructures in ALH84001 claimed to be of biogenic originA meteorite originating from Mars known as ALH84001 was shown in 1996 to contain microscopic structures resembling small terrestrial nanobacteria....

On May 11, 2001, two researchers from the University of Naples claimed to have found live extraterrestrial bacteria inside a meteorite...
An Indian and British team of researchers led by Chandra Wickramasinghe reported on 2001 that air samples over Hyderabad, India, gathered from the stratosphere by the Indian Space Research Organization, contained clumps of living cells. Wickramasinghe calls this "unambiguous evidence for the presence of clumps of living cells in air samples from as high as 41 km, above which no air from lower down would normally be transported...Pushkar Ganesh Vaidya from the Indian Astrobiology Research Centre reported in his 2009 paper that "the three microorganisms captured during the balloon experiment do not exhibit any distinct adaptations expected to be seen in microorganisms occupying a cometary niche".[59][60]

In 2005 an improved experiment was conducted by ISRO. On April 10, 2005 air samples were collected from six places at different altitudes from the earth ranging from 20 km to more than 40 km. Adequate precautions were taken to rule out any contamination from any microorganisms already present in the collection tubes. The samples were tested at two labs in India. The labs found 12 bacterial and 6 fungal colonies in these samples... Out of the 12 bacterial samples, three were identified as new species and named Janibacter hoyeli.sp.nov (after Fred Hoyle), Bacillus isronensis.sp.nov (named after ISRO) and Bacillus aryabhati (named after the ancient Indian mathematician, Aryabhata). These three new species showed that they were more resistant to UV radiation than similar bacteria found on Earth.

A NASA research group found a small number of Streptococcus mitis bacteria living inside the camera of the Surveyor 3 spacecraft when it was brought back to Earth by Apollo 12. They believed that the bacteria survived since the time of the craft's launch to the Moon.
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  None of these are conclusive, even for the finding of previously unknown life at 40km, it getting there from Earth's surface by some unknown weather combination cannot be entirely excluded. Equally spectrographic analysis of galactic light is more consistent with complex hollow carbon based structures than simple ones

  But there are a lot of separate pieces of evidence and no actual evidence that life originated here. The only reason for expecting a terrestrial origin, and it is a strong one I have used before, is that if life is common we should have expected the development of intelligent life and its settlement of the galaxy long before we came down form the trees.

 Other reading

  Cosmic Ancestry - book length series of articles.

  Panspermia Theory


  Wickramasinghe interview

  The argument for and indeed against panspermia does suffer from a lack of evidence. I will discuss how to change that tomorrow. And philosophical implications after.