Earth And Moon
Taxes are rising on this planet. NASA

If we ever do make contact with aliens, they might turn out to be be our long-lost -- and very removed -- cousins. For years, scientists have wondered whether life on Earth could have been seeded by extraterrestrial sources, but perhaps they weren’t looking at it from all possible perspectives.

In a new paper published in the journal Astrobiology, a group of scientists argues that while it’s feasible that some of the organisms around us may be extraterrestrial in origin, it is equally possible that life originating on Earth could have been flung into space on the backs of rocks. The concept is called “lithopanspermia,” and, until recently, scientists thought it was nigh on impossible for microbe-laden meteorites to escape our solar system’s gravitational pull.

Using a mathematical model, researchers from New York University, Princeton University, and the University of Arizona calculated that at least 100 trillion and as many as 30 quadrillion fragments of matter more than 10 kilograms in size may have been exchanged between nearby systems and our solar system -- many more than previously estimated.

They think that the rocks were moving slower than previous estimates, which allows for a process called “weak transfer,” where a slow-moving object slips from one larger body’s weak grip on it and into the gravitational well of another planetary system.

However, the only time when these kinds of transfers could have happened, the researchers reported, was between 164 million and 288 million years after the solar system formed. That’s a bit earlier than when the earliest known microorganisms began to show up, but not so long ago as to be implausible.

Still, the current work merely shows that it’s possible for life-carrying rocks to be transferred between planets, not whether it’s likely that life has taken root outside our solar system.

“Our study stops when the solid matter is trapped by the second planetary system, but for lithopanspermia to be completed it actually needs to land on a terrestrial planet where life could flourish,” author and Princeton researcher Amaya Moro-Martin said in a statement. “The study of the probability of landing on a terrestrial planet is work that we now know is worth doing because large quantities of solid material originating from the first planetary system may be trapped by the second planetary system, waiting to land on a terrestrial planet.”

Source: Belbruno et al. “Chaotic Exchange of Solid Material Between Planetary Systems: Implications for Lithopanspermia.” Astrobiology 12: 754-774, August 2012.