Theoretical origin of life: panspermia again (Introduction)

by David Turell , Sunday, February 18, 2024, 18:59 (69 days ago) @ David Turell

An article with a highly critical conclusion:

https://www.sciencealert.com/life-spreads-across-space-on-tiny-invisible-particles-stud...

New research examines the idea that cosmic dust could be responsible for spreading life throughout the galaxy by panspermia. Life arose elsewhere, and was delivered to the young Earth. This is not a new idea, but in this work, the author calculates how quickly it could happen.

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No matter how much we ponder and investigate the origins of life, we don't know how it starts. We have an idea about the type of environment that could spawn it, but even that is an idea obscured by billions of years.

"It is clear that the main problem is the origin of life or abiogenesis, the details of which are still unknown to us," Osmanov writes.

But it started somehow. Leaving life's original appearance aside, for now, Osmanov moves on to how it could spread.

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The idea that life itself could travel through space on comets and asteroids is familiar to many people. When these objects crash into planets, the thinking goes, hitchhiking life is delivered, and if there's a niche it can exploit, it will. But how could simple dust accomplish the same thing?

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A 2017 paper in the journal Astrobiology showed how hypervelocity space dust can interact with this Earth dust, creating powerful momentum flows. A small fraction of the planetary dust particles can be accelerated enough to escape the planet's gravity.

Once free of its planet's gravity, dust is then at the mercy of stellar radiation pressure.

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Life would need to be very hardy to survive on a dust grain as it travels through interstellar space. It would have to avoid hazards like radiation and heat. If life itself couldn't do it, maybe complex molecules that lead to life could. If we grant that it's possible, the next question concerns how quickly it could spread.

"It has been shown that, during 5 billion years, the dust grains will reach 105 stellar systems, and by taking the Drake equation into account, it has been shown that the whole galaxy will be full of planetary dust particles," Osmanov explains.

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"In particular, it has been pointed out that, by means of the solar radiation pressure, small dust grains containing live organisms can travel to the nearest solar system, Alpha Centauri, in nine thousand years," Osmanov writes. Our powerful rockets, like the Space Launch System and the Falcon Heavy, would take over 100,000 years to make the journey.

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He takes a bold step beyond our current knowledge when he writes, "On the other hand, it is natural to assume that the number of planets with at least primitive life should be enormous." It might be a natural assumption, but there's little evidence that it's true. It's conjecture, stimulating conjecture, but conjecture nonetheless. (my bold)

Working with a statistical approach to the Drake Equation, Osmanov writes that the number of planets that developed life is on "the order of 3×107."

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It's very interesting work. But the frustrating thing about this entire topic is that we still don't know how life appears or how often it appears. So, all of our thought experiments and calculations, including Osmanov's, have a stubborn nugget of the unknown at the centre.
(my bold)

Osmanov claims that the number of planets with primitive life is enormous. We don't know that. Planets are extraordinarily complex, and there are a bewildering number of variables. Even if there are an enormous number of planets with primitive life, many of them will be more massive than Earth. Will dust particles carrying life or complex organic molecules be able to escape the gravitational grasp of super-Earths, for example?

This research shows how life, or at least its building blocks, could escape from planets and survive the interstellar journey to another world. If it's true, and panspermia can account for life appearing on Earth so soon after it formed and cooled, then it changes our understanding of our origins and even the rest of the Universe.

But we don't know how true it is, and we still don't know how it starts.(my bold)

Comment: finally, a non-sensationalist science writer with as brain. Panspermia is a nutty theory with no real answers. It is no solution to the question of how life started.