Life Could Spread Across The Galaxy On Cosmic Dust, Wild New Paper Suggests

A new paper has taken a look at panspermia and the suggestion that dust particles could escape the gravity of host planets and make their way across the galaxy, seeding life on other planets.

There are a number of ideas about how life began on Earth, with the most likely being that it emerged in hydrothermal vents in the oceans billions of years in the past. But not all theories have Earth as the beginning place of life on Earth. One theory, which would still leave us with the problem of how life initially began, is that life could be carried across the Solar System, or perhaps even the galaxy. 

The idea, known as panspermia, has been around in various forms for centuries, but was named in the early 1900s by Swedish scientist Svante Arrhenius. Arrhenius suggested that small dust grains containing live organisms could be carried out of a planet’s atmosphere, and then propelled across space by solar radiation pressure. 

Putting aside whether life – even hardy life – could survive the arduous journeys involved, various astronomers have attempted to calculate how long it would take life to radiate out from a planet in this way. One team concluded that it would take around 20 days for life to make it to Mars from Earth, 14 months to get to Neptune, and 9,000 years to get to Alpha Centauri – a long time for humans, but a blink of an eye in cosmic terms.

Previous research has shown that small amounts of dust grains at high altitudes could gain escape velocity by colliding with cosmic dust particles, starting their journey across the cosmos. In a new preprint paper, yet to be published in a peer-reviewed journal, physicist Zaza N. Osmanov attempted to calculate the spread of this life across the galaxy, if indeed it is able to survive the journey. Despite the distances involved, travel by this method looks pretty viable, according to the paper.

“We have considered the dynamics of planetary dust particles ‘propelled’ by planets, and it has been shown that in 5 billion years, dust grains can travel in the [interstellar medium] at distances of the order of several hundred light-years,” Osmanov concluded. “By taking the stellar distribution density into account, we have found that dust particles emitted by every single planet will reach as much as 105 stellar systems.”

Despite this intriguing idea, Osmanov also found problems for fans of the panspermia concept, in that dense molecular clouds may trap planetary dust grains as they fly through the galaxy. However, as usual, the bigger problem might be fueling the Fermi Paradox.

 

“Analyzing the problem in the context of the Drake equation, it has been found that the minimum number of planets in the Milky Way that have developed life should be of the order of 3 × 107,” Osmanov wrote, “implying that the whole galaxy will be full of dust particles with complex molecules.”

For that life to take hold, it would still need to find itself on planets with favorable conditions, but if there is life out there, according to this paper it should be seeding other life elsewhere, leading us to once again ask: Where is everybody?

The paper, as-yet unpublished, is available on preprint server arXiv.

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