Panspermia, Octopuses, and Comets 4/6

Interstellar bacteria and mass extinctions

Credit: David A. Aguilar / CfA —According to the panspermia hypothesis, around 4 billion years ago, on a young Earth with an atmosphere still devoid of oxygen, frequent impacts of asteroids and comets deposited tons of biological material of extraterrestrial origin in the oceans. As soon as the environmental conditions allowed it, organisms from space managed to survive and reproduce, transforming the Earth into a place teeming with life — a life that still flourishes, despite cataclysms of all kinds and periodic mass extinctions

Bacteria from space

Regarding the incredible replication power of bacteria, in their 1999 book “Astronomical origins of life,” Hoyle and Wickramasinghe wrote (page 101):

Start with a single living cell, say a bacterium. A typical doubling time by binary-fission for a bacterium supplied with appropriate nutrients would be two or three hours. Continuing to supply materials, the initial bacterium would generate some 2⁴⁰ bacteria in 4 days, yielding a culture of the size of a pinhead. Continuing for a further 4 days and the culture, now containing 2⁸⁰ bacteria, would have the size of a village pond. Another 4 days and the resulting 10¹²⁰ bacteria would have the scale of the Pacific Ocean. Yet another 4 days and the 10¹⁶⁰ bacteria would in quantity be comparable to a molecular cloud like the Orion Nebula, and another 4 days, bringing the total time interval to only 20 days, and the scale in quantity would be that of a million or more galaxies. In a year there would be some 2³⁶⁵⁰ bacteria and in a thousand years the total would be 2³⁶⁵⁰⁰⁰⁰ bacteria. Thus biology yields superastronomical numbers as well as depending on them.

The two authors were convinced that interstellar dust clouds teemed with microbial life, whose signature…