Comets and life 3

04/06/2010

Updating Comets and Magic Universe

Did comets spark life on Earth?

Part 3 Initiating biochemical action

Pascale Ehrenfreund rides again (as in Part 2) in the story in Magic Universe called “Life’s origin: will the answer to the riddle come from outer space?”. But please focus first on Wlodzimierz Lugowsky.

I can trace my ancestry back to a protoplasmal primordial atomic globule,’ boasts Pooh-Bah in The Mikado. When Gilbert and Sullivan wrote their comic opera in 1885 they were au courant with science as well as snobbery. A century later, molecular biologists had traced the genetic mutations, and constructed a single family tree for all the world’s organisms that stretched back 4 billion years ago, to when life on Earth probably began. But they were scarcely wiser than Pooh-Bah about the precise nature of the primordial protoplasm.

In 1995 Wlodzimierz Lugowsky of Poland’s Institute of Philosophy and Sociology wrote about ‘the philosophical foundations of protobiology’. He listed nearly 150 scenarios then on offer for the origin of life and, with a possible single exception to be mentioned later, he judged none of them to be satisfactory. Here is one of the top conundrums for 21st Century science. The origin of life ranks with the question of what initiated the Big Bang, as an embarrassing lacuna in the attempt by scientists to explain our existence in the cosmos.

After discussing possible “home cooking” of life by hypercycles, RNA catalysis or lipid catalysis, and touching on the possibility of false starts, the tale turns back to the sky in pursuit of the only hypothesis acceptable to Lugowsky.

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Comets and life 2

01/06/2010

Updating Comets and Magic Universe

Did comets spark life on Earth?

Part 2: Cosmic carbon compounds

An earlier post, Part 1 under this heading, commented enthusiastically but briefly on a French team’s find of extraterrestrial dust grains rich in carbon in the snow of Antarctica. https://calderup.wordpress.com/2010/05/10/comets-and-life/

I promised more to come, and here it begins. Part 2 deals with cosmic carbon compounds. Later, Part 3 will reconsider the initiation of biochemical action, and Part 4 will look at suggestions of natural life footloose in space.

There were far more comets around when the Solar System was young, in the “heavy bombardment” phase of Earth history lasting until 3.8 billion years ago. Water is abundant in interstellar space and available to build the icy nuclei of comets. Comets may have delivered most of the Earth’s surface water, essential for life.

Carbon compounds are the other main ingredient for life. Comets’ tails consist mainly of small dust grains released from the nuclei, including grains laden with carbon compounds that may have contributed to the origin of life on the Earth. Here’s a general impression of important “prebiotic” molecules made in the vicinity of dying stars and newborn stars and available for incorporation into comets.

PAHs, polyaromatic hydrocarbons observable in interstellar space, could be ancestral to the aromatic compounds that have the very smell of life. Illustration from Pascale Ehrenfreund & Steven Charnley, 2000 – see reference. Graphic art: ©2000 R. Ruiterkamp


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