Could there be galactic panspermia?

US study on panspermia Interstellar objects could spread life in space

Did life on earth develop independently or was it brought here from the vastness of the universe? Supporters of the panspermia hypothesis believe in the latter. For the majority of scientists, this has so far been pure speculation.

Oumuamua fuels panspermia debate

The appearance of the football field-sized, cigar-shaped interstellar object "Oumuamua" in our solar system has rekindled the discussion about the rocks that microbes spread across the universe over great distances. Scientists at the prestigious Harvard-Smithsonian Center for Astrophysics like astrophysicist Idan Ginsburg conclude in a new study: "Life could potentially be exchanged over thousands of light years."

Arguments of the opponents

The opponents of the panspermia hypothesis have so far argued that it would take millions of years for meteorites or other celestial bodies to be catapulted out of a solar system such as ours and put on their way to another solar system. Even the most robust bacteria or spores would not survive such a long period under the conditions of a vacuum and cosmic rays. In addition, according to another argument of the panspermia skeptics, only a tiny amount of the rock would be captured again by a remote system.

But-quadrillion chunks while traveling

The supporters of the panspermia hypothesis, however, see their view confirmed by the appearance of "Oumuamua" in our solar system that simple life forms on interstellar objects can travel from one star system to another. With a view to the limited region of space that the telescopes examined for the discovery of "Oumuamua", they can refer to a recent study, according to which in our galaxy alone - the Milky Way - one trillion such objects per cubic light year travel should be. To fill such a space, it would mean that each star system in the Milky Way would have to eject 10 quadrillion such objects, some of which could pass through our solar system at any point in time.

"It happens quite often"

On the basis of such calculations, the Smithsonian astrophysicists assume that double stars (two stars that are so close together that they look like a star) such as Alpha Centauri, due to their more complex gravitational field, several thousand chunks the size of "Oumuamua" per year "could attract. For our - simple - solar system this would mean that one such chunk could still be attracted per century. According to US scientists, that would be around 10 million objects that could be "captured" somewhere in the Milky Way in a million years. "So if you look at the galaxy as a whole, you have to suspect that this happens quite often," says Ginsburg.

No mathematically exact basis

Critics such as the astronomer Ed Turner from Princeton University counter the authors of the Smithsonian study, however, by sticking too much to the example of "Oumuamua" and not offering a mathematically exact basis for their thesis. Other skeptics argue that even if our galaxy were full of "Oumuamuas", it is still unlikely that these could be carriers of panspermia.

Hope for more data

The Smithonian astrophysicists, however, point out that even more secure data and the discovery of further interstellar objects could clarify whether the thesis of galactic panspermia is plausible. Only the discovery of life in another world could reveal whether life originated in a certain place in the galaxy and spread from there over vast distances and periods of time through the great emptiness of space.