The theory of panspermia is a controversial one, to say the least. It has various forms, but the crux is this: Life originated beyond the Solar System and was spread through the galaxy, perhaps via drifting microbes, asteroids or even artificially by intelligent beings. It’s fair to say that it has split opinion over the years.
One team of researchers, though, has taken a look not at how panspermia might work, but instead how we might prove or disprove it. At first, the research seems fanciful, but delving into it reveals some rather interesting ideas. Their research has been accepted for publication in The Astrophysical Journal Letters.
The Harvard astrophysicists, led by Henry Lin of the Harvard-Smithsonian Center for Astrophysics (CfA), speculated that there could – strong emphasis on could – be “oases” of life throughout the galaxy, from which life in our own Solar System, and others, began. To prove this is the case, they say we would need to be able to rewind the motion of all stars in the galaxy. If we can find other worlds that bear life, and see that they all came from the same place, then it would suggest panspermia is possible.
“The point of the paper is not to develop the theory of panspermia,” Lin told IFLScience. “The point of the paper is that, given we don’t know how panspermia happens, or even if it happened, is there some generic observable that we can imagine measuring in a few decades that would allow us to determine experimentally whether this occurs. The answer, in a variety of scenarios, is yes.”
Lin says that if we look at one portion of the sky and find it is abundant in life, whereas another is devoid of it, it suggests that it has spread selectively rather than at random. It would be a “smoking gun” for panspermia. If the reverse is true, it means panspermia is unlikely to have occurred.
“The question is, is life more like a genetic disease, it doesn’t matter where you are. Or is it an epidemic, where it spreads from place to place,” said Lin.
For panspermia to be detectable, Lin notes that it must be relatively quick. If life did spread out from oases across the galaxy, it would have needed to travel faster than 10 kilometers (6.2 miles) per second relative to other stars in order to catch up. “If life travels much slower, say 0.01 kilometers (0.006 miles) per second, then the motion of stars is much faster and the spread of life would be very hard to detect,” said Lin.
Of course, this all depends on one glaring problem: Actually finding other life. At the moment, we only have one example, our planet Earth, from where all our theories are extrapolated. But Lin is confident. “I’m sure we’ll find something interesting,” he said. And he noted that upcoming telescopes like the James Webb Space Telescope (JWST) could set us on the way to proving or disproving panspermia by observing stars and planets.
Love it or loathe it, the theory of panspermia is here to stay. For now.