Comets and life 5


Updating Comets and Magic Universe

Did comets spark life on Earth?

Part 5: Summary

It’s in the nature of blogs that developing stories come out backwards. So it may be helpful to summarize the key updates that have arisen.

Comets and life 1 – Recent news: ultra-clean snow melted and sieved for meteoritic particles, at the French-Italian CONCORDIA station in Antarctica, yielded UCAMMs [ultra-carbonaceous Antarctic micrometeorites] with very high carbon contents. Larry Nittler says they “may well have profound implications for the original delivery of organic molecules to the early Earth”.

Comets and life 2 – I did not err in betting heavily in Magic Universe on the magic of polycyclic aromatic hydrocarbons, PAHs. Pascale Ehrenfreund says, “We suggest the aromatic material can be used as a container, as a metabolic unit, and as a genetic information carrier.”

Comets and life 3 – Both Jochen Kissel as instigator and I as reporter remain persuaded that the Kissel-Krueger hypothesis, that chemically active materials from outer space interacted with water to create the first living cells, is still the most promising explanation for the origin of life on the Earth.

Comets and life 4 – I now accept Hoyle & Wickramasinghe’s idea, about pre-existing bacteria in space being rehydrated by the Earth’s water, as another promising hypothesis. And here I repeat what I said at the very end of part 4.

I share Wickramasinghe’s concern about the “cultural barrier”. Science became over-specialized in the creation of university departments in the 19th Century. Since then, in several major advances, earth scientists and biologists offered strong and prolonged resistance when astronomers and astronomically-minded folk said:

  • extinctions due to impacting comets and asteroids have redirected the course of evolution (Halley, about a comet)
  • the Earth’s wobbly orbit around the Sun sets the timing of coolings and warmings in the ice ages (Milankovitch)
  • to explain the origin of life on Earth we have to consider possible cosmic sources (Arrhenius)
  • to understand climate change we have to look to the role of cosmic rays in cloud formation (Svensmark)

Plus ça change, plus c’est la même chose.

You can see all parts of the story (in reverse order) just by clicking on 1c) Comets in the Categories menu.

Or individually:

Part 1

Part 2

Part 3

Part 4


Comets and life 4


Updating Comets and Magic Universe

Did comets spark life on Earth?

Part 4: Life footloose in space

In Part 1 of this series, I mentioned that in Comets, written 30 years ago, I made fun of propositions from the astrophysicists Fred Hoyle and Chandra Wickramasinghe about viable entities living in comets and being delivered ready-made to the Earth, scattered from the comets’ tails. What follows fulfils a promise to look at Chandra’s present ideas — I hope with an open mind.

To back-track a little, there’s a 100-year history of eminent scientists, driven by despair about explaining the very improbable chemistry of life by home cooking on the Earth, suggesting that life came from elsewhere. Of course, their scenarios didn’t explain the origin of life, they merely transferred it somewhere else. Out of sight, out of mind, perhaps.

  • 1907 Svante Arrhenius (yes, the CO2 warming pioneer) suggested that bacterial spores escaped from an alien planet, were driven through interstellar space by the pressure of sunlight, and revived when they reached the Earth.
  • 1971 Francis Crick (yes, of DNA fame) with Leslie Orgel proposed that intelligent beings in another part of the Galaxy spotted the Earth as a suitably wet planet and sent bacteria in a spaceship to seed it.
  • 1979 Fred Hoyle (yes, celebrated for the origin of the elements) with Chandra Wickramasinghe said that life on Earth began in comets, and diseases still come from them.

It was hard not to chuckle over their book Diseases from Space, because Hoyle and Wickramasinghe’s account filled the sky with germs, in a distant echo of the old superstition that comets portended plagues.

John Gadbury (1665) linked comets and catastrophes -- "Famine, Plague & Warrs" In actuality, bubonic plague afflicted London following the depicted 1664-5 comet. Obtained from the Royal Astronomical Society, this is an illustration in N. Calder, Comets: Speculation and Discovery.

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