Cosmic Dust Could Spread Life from World to World Across the Galaxy

Could life spread throughout the galaxy on tiny grains of dust? It would be a perilous journey, but new research shows its possible and calculates how long it would take to spread. Image Credit: ESO

Does life appear independently on different planets in the galaxy? Or does it spread from world to world? Or does it do both?

New research shows how life could spread via a basic, simple pathway: cosmic dust.

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Since Interstellar Objects Crashed Into Earth in the Past, Could They Have Brought Life?

Artist’s impression of the interstellar object, `Oumuamua, experiencing outgassing as it leaves our Solar System. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

On October 19th, 2017, astronomers with the Pan-STARRS survey detected an interstellar object (ISO) passing through our Solar System for the first time. The object, known as 1I/2017 U1 Oumuamua, stimulated significant scientific debate and is still controversial today. One thing that all could agree on was that the detection of this object indicated that ISOs regularly enter our Solar System. What’s more, subsequent research has revealed that, on occasion, some of these objects come to Earth as meteorites and impact the surface.

This raises a very important question: if ISOs have been coming to Earth for billions of years, could it be that they brought the ingredients for life with them? In a recent paper, a team of researchers considered the implications of ISOs being responsible for panspermia – the theory that the seeds of life exist throughout the Universe and are distributed by asteroids, comets, and other celestial objects. According to their results, ISOs can potentially seed hundreds of thousands (or possibly billions) of Earth-like planets throughout the Milky Way.

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Rogue Planets Could be Habitable

An artist's illustration of a rogue planet, dark and mysterious. Image Credit: NASA

The search for potentially habitable planets is focused on exoplanets—planets orbiting other stars—for good reason. The only planet we know of with life is Earth and sunlight fuels life here. But some estimates say there are many more rogue planets roaming through space, not bound to or warmed by any star.

Could some of them support life?

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Galactic Panspermia. How far Could Life Spread Naturally in a Galaxy Like the Milky Way?

A new study expands on the classical theory of panspermia, addressing whether or not life could be distributed on a galactic scale. Credit: NASA

Can life spread throughout a galaxy like the Milky Way without technological intervention? That question is largely unanswered. A new study is taking a swing at that question by using a simulated galaxy that’s similar to the Milky Way. Then they investigated that model to see how organic compounds might move between its star systems.

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Earth’s toughest bacteria can survive unprotected in space for at least a year

Credit: Ott, E., Kawaguchi, Y., Kölbl, D. et al.

A remarkable microbe named Deinococcus radiodurans (the name comes from the Greek deinos meaning terrible, kokkos meaning grain or berry, radius meaning radiation, and durare meaning surviving or withstanding) has survived a full year in the harsh environment of outer space aboard (but NOT inside) the International Space Station. This plucky prokaryote is affectionately known by fans as Conan the Bacterium, as seen in this classic 1990s NASA article.

The JAXA (Japanese Aerospace Exploration Agency) ISS module Kib? has an unusual feature for spacecraft, a front porch! This exterior portion of the space station is fitted with robotic equipment to complete various experiments in outer space’s brutal conditions. One of these experiments was to expose cells of D. radiodurans for a year and then test the cells to see if they not only would survive but could reproduce effectively afterward. D. radiodurans proved to be up to the challenge, and what a challenge it was!

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Astronomers Finally Think They Understand Where Interstellar Object Oumuamua Came From and How it Formed

Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

‘Oumuamua caused quite a stir when it visited our Solar System in 2017. It didn’t stay long, however, and when it was spotted with the Pan-STARRS telescope in Hawaii on October 19th, it was already leaving. But its appearance in our part of the Universe spawned a lot of conjecture on its nature and its origins.

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A Microorganism With a Taste for Meteorites Could Help us Understand the Formation of Life on Earth

Credit: University of Vienna

From the study of meteorite fragments that have fallen to Earth, scientists have confirmed that bacteria can not only survive the harsh conditions of space but can transport biological material between planets. Because of how common meteorite impacts were when life emerged on Earth (ca. 4 billion years ago), scientists have been pondering whether they may have delivered the necessary ingredients for life to thrive.

In a recent study, an international team led by astrobiologist Tetyana Milojevic from the University of Vienna examined a specific type of ancient bacteria that are known to thrive on extraterrestrial meteorites. By examining a meteorite that contained traces of this bacteria, the team determined that these bacteria prefer to feed on meteors – a find which could provide insight into how life emerged on Earth.

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Comets and Interstellar Objects Could be Exporting Earth Life Out into the Milky Way

An artist’s overview of the mission concept for the Comet Interceptor spacecraft, which will fly from the vicinity of Earth to rendezvous with a long-period comet or interstellar object inbound from the outer solar system. Credit: ESA

For over a century, proponents of Panspermia have argued that life is distributed throughout our galaxy by comets, asteroids, space dust, and planetoids. But in recent years, scientists have argued that this type of distribution may go beyond star systems and be intergalactic in scale. Some have even proposed intriguing new mechanisms for how this distribution could take place.

For instance, it is generally argued that meteorite and asteroid impacts are responsible for kicking up the material that would transport microbes to other planets. However, in a recent study, two Harvard astronomers examine the challenges that this would present and suggest another means – Earth-grazing objects that collect microbes from our atmosphere and then get flung into deep-space.

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The Milky Way Could Be Spreading Life From Star to Star

Using information from Gaia's second data release, a team of scientists have made refined estimates of the Milky Way's mass. Credit: ESA/Gaia/DPAC

For almost two centuries, scientists have theorized that life may be distributed throughout the Universe by meteoroids, asteroids, planetoids, and other astronomical objects. This theory, known as Panspermia, is based on the idea that microorganisms and the chemical precursors of life are able to survive being transported from one star system to the next.

Expanding on this theory, a team of researchers from the Harvard Smithsonian Center for Astrophysics (CfA) conducted a study that considered whether panspermia could be possible on a galactic scale. According to the model they created, they determined that the entire Milky Way (and even other galaxies) could be exchanging the components necessary for life.

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The Solar System Probably has Thousands of Captured Interstellar Asteroids

Artist’s impression of the first interstellar asteroid/comet, "Oumuamua". This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) in Hawaii announced the first-ever detection of an interstellar asteroid, named 1I/2017 U1 (aka. ‘Oumuamua). Originally thought to be a comet, this interstellar visitor quickly became the focus of follow-up studies that sought to determine its origin, structure, composition, and rule out the possibility that it was an alien spacecraft!

While ‘Oumuamua is the first known example of an interstellar asteroid reaching our Solar System, scientists have long suspected that such visitors are a regular occurrence. Aiming to determine just how common, a team of researchers from Harvard University conducted a study to measure the capture rate of interstellar asteroids and comets, and what role they may play in the spread of life throughout the Universe.

The study, titled “Implications of Captured Interstellar Objects for Panspermia and Extraterrestrial Life“, recently appeared online and is being considered for publication in The Astrophysical Journal. The study was conducted by Manasavi Lingam, a postdoc at the Harvard Institute for Theory and Computation (ITC), and Abraham Loeb, the chairman of the ITC and a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA).

For the sake of their study, Lingam and Loeb constructed a three-body gravitational model, where the physics of three bodies are used to compute their respective trajectories and interactions with one another. In Lingam and Loeb’s model, Jupiter and the Sun served as the two massive bodies while a far less massive interstellar object served as the third. As Dr. Loeb explained to Universe Today via email:

“The combined gravity of the Sun and Jupiter acts as a ‘fishing net’. We suggest a new approach to searching for life, which is to examine the interstellar objects captured by this fishing net instead of the traditional approach of looking through telescope or traveling with spacecrafts to distant environments to do the same.”

Using this model, the pair then began calculating the rate at which objects comparable in size to ‘Oumuamua would be captured by the Solar System, and how often such objects would collide with the Earth over the course of its entire history. They also considered the Alpha Centauri system as a separate case for the sake of comparison. In this binary system, Alpha Centauri A and B serve as the two massive bodies and an interstellar asteroid as the third.

As Dr. Lingam indicated:

“The frequency of these objects is determined from the number density of such objects, which has been recently updated based on the discovery of ‘Oumuamua. The size distribution of these objects is unknown (and serves as a free parameter in our model), but for the sake of obtaining quantitative results, we assumed that it was similar to that of comets within our Solar System.”

The theory of Lithopanspermia states that life can be shared between planets within a planetary system. Credit: NASA

In the end, they determined that a few thousands captured objects might be found within the Solar system at any time – the largest of which would be tens of km in radius. For the Alpha Centauri system, the results were even more interesting. Based on the likely rate of capture, and the maximum size of a captured object, they determined that even Earth-sized objects could have been captured in the course of the system’s history.

In other words, Alpha Centauri may have picked up some rogue planets over time, which would have had drastic impact on the evolution  of the system. In this vein, the authors also explored how objects like ‘Oumuamua could have played a role in the distribution of life throughout the Universe via rocky bodies. This is a variation on the theory of lithopanspermia, where microbial life is shared between planets thanks to asteroids, comets and meteors.

In this scenario, interstellar asteroids, which originate in distant star systems, would be the be carriers of microbial life from one system to another. If such asteroids collided with Earth in the past, they could be responsible for seeding our planet and leading to the emergence of life as we know it. As Lingam explained:

“These interstellar objects could either crash directly into a planet and thus seed it with life, or be captured into the planetary system and undergo further collisions within that system to yield interplanetary panspermia (the second scenario is more likely when the captured object is large, for e.g. a fraction of the Earth’s radius).”

In addition, Lingam and Loeb offered suggestions on how future visitors to our Solar System could be studied. As Lingam summarized, the key would be to look for specific kinds of spectra from objects in our Solar Systems:

“It may be possible to look for interstellar objects (captured/unbound) in our Solar system by looking at their trajectories in detail. Alternatively, since many objects within the Solar system have similar ratios of oxygen isotopes, finding objects with very different isotopic ratios could indicate their interstellar origin. The isotope ratios can be determined through high-resolution spectroscopy if and when interstellar comets approach close to the Sun.”

“The simplest way to single out the objects who originated outside the Solar System, is to examine the abundance ratio of oxygen isotopes in the water vapor that makes their cometary tails,” added Loeb. “This can be done through high resolution spectroscopy. After identifying a trapped interstellar object, we could launch a probe that will search on its surface for signatures of primitive life or artifacts of a technological civilization.”

It would be no exaggeration to say that the discovery of ‘Oumuamua has set off something of a revolution in astronomy. In addition to validating something astronomers have long suspected, it has also provided new opportunities for research and the testing of scientific theories (such as lithopanspermia).

In the future, with any luck, robotic missions will be dispatched to these bodies to conduct direct studies and maybe even sample return missions. What these reveal about our Universe, and maybe even the spread of life throughout, is sure to be very illuminating!

Further Reading: arXiv