Evidence of microbes from outer space


LONDON — The biggest news so far this year is not George W. Bush’s plans for intergalactic defense, or even the Code Red virus that was supposed to eat our computers and then our brains. It is the discovery of bugs in the upper atmosphere.

“There is now unambiguous evidence for the presence of clumps of living cells in air samples from as high as 41 kilometers, well above the local tropopause above which no air from lower down would normally be transported,” Professor Chandra Wickramasinghe told the International Society for Optical Engineering in San Diego last week. Wickramasinghe’s home base, Cardiff University, says it is “the first positive identification of extra-terrestrial microbial life.”

According to Wickramasinghe’s 10-person team of scientists, there are living cells in the upper atmosphere of this planet that probably come from space. They are also suggesting that living cells arriving from outer space were the mechanism by which life first arose on this planet — with the further implications that life exists on almost every planet, and that all life in this galaxy is genetically related.

That is rather a lot to deduce from a balloon collecting air samples in the stratosphere, even if it went twice as high as any balloon on such a mission has ever gone before, but the Cardiff University team were not surprised. “We have argued for more than two decades that terrestrial life was brought down to Earth by comets,” said Wickramasinghe, “and that cometary material containing micro-organisms must still be reaching us in large quantities.”

The hypothesis of the Cardiff University team, originally led by brilliant cosmologist Sir Fred Hoyle, has never been completely dismissed by more orthodox scientists because their credentials were so strong. (Hoyle was the man who worked out how the heavier elements in the universe are created in the hearts of dying stars.) But what they were saying was so contrary to conventional scientific wisdom that they were mostly politely ignored.

The conventional wisdom states that life on Earth arose from the soup of organic chemicals that existed on the primordial surface of the planet. Simple experiments have shown that the gases that then made up the Earth’s atmosphere, when zapped with electrical charges of the sort that lightning would have provided, combine readily into organic molecules. It’s a very long way from those to the first living cell, but there were several billion years for evolution to work its magic.

Hoyle and Wickramasinghe began suggesting, as long ago as 1974, that while the evolutionary process leading to the first living cell undoubtedly happened somewhere, some time, it probably occurred far, far away, long before the Earth had even cooled. Their starting point was the then-new observation that even the interstellar gas clouds contain organic molecules. Their radical suggestion was that the millions of comets that shuttle between the interstellar depths and the inner solar system were the conveyor belt that brought this organic material, perhaps including even living cells, to Earth.

At the time, it was an unprovable theory, but recently space probes have found evidence that comets contain chemical material similar to the cell walls of living organisms. Meanwhile, Wickramasinghe’s team reasoned that if comets are constantly delivering living cells to the inner solar system that are then swept up by the Earth as it orbits the sun, then we should be able to find those cells in the upper atmosphere.

The consensus among meteorologists is that there is normally no mixing between the lower atmosphere (the troposphere), where all earthly life exists, and the upper atmosphere or stratosphere. If you did find living cells above the tropopause (the barrier between the two), they would likely have come from space, not from the Earth. So the Cardiff team sent up giant balloons from a research base near Hyderabad in India, collected air samples at altitudes of up to 41 km, and found bacteria.

“Clumps of living cells were found at all altitudes using this technique,” they wrote in their report. “Since the 41-km sample was collected well above the local tropopause, a prima facie case for a space incidence of these micro-organisms is established.”

It takes a long time in science before any controversial proposition is accepted as valid. Maybe the Cardiff team’s equipment was contaminated by earthly bacteria. Maybe a passing rocket carried bacteria up into the stratosphere. But these are serious scientists who foresaw all the objections and structured the experiment accordingly.

Devices on the balloons kept the air samples in sterile conditions while fluorescent dyes that are only absorbed by the membranes of living cells were used to detect the bacteria. Electron microscope images showed coral-like clumps of cells between 5 and 15 micrometers across. And the samples taken from higher altitudes contained more of them than the lower samples, suggesting that they were falling from space.

If Wickramasinghe’s conclusion is correct, then this is one of the most important discoveries of all time. It would mean that throughout this galaxy and beyond, all environments even marginally hospitable to life are actually inhabited by living things, for the microbial seeds fall from space on every available surface (which probably means hundreds of millions of planets in our galaxy alone).

It would also mean that all life forms — you, me, the cloud creatures of Betelguese and even the dreaded Bugblatter Beast of Rigel X — have a common origin in space-borne micro-organisms and are thus intimately related to each other.