Whether or not we’re alone in the universe is one of humanity and science’s most enduring questions. But now a new paper is asking whether or not we’re even alone on Earth.
The theory was published this month in the International Journal of Astrobiology and proposes the possibility that sub-micron sized alien fossils or minerals may be floating through space or even buried deep under our planet’s oceans or ice sheets as the result of asteroid impacts on other planets. The paper’s author and University of Tokyo professor of astronomy, Tomonori Totani, told Motherboard that devising ways to find these particles on Earth could help identify alien biosignatures that established methods—like searching radio signals for so-called technosignatures or analyzing the atmospheres of exoplanets—miss.
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According to Totani’s rough estimates, 100,000 of these grains may be falling on Earth every year. Identifying a biosignature from even one of these grains could transform how we understand life in our universe.
“I have been interested in the origin of life,” Totani said, referring to a 2020 paper in the journal Scientific Reports he wrote on the subject. “I wondered if there is a different approach for more direct sampling of extrasolar biological materials, then I got this idea. It is more direct than remote astronomical observations, because grains may include fossils of microbes, which will never be obtained by remote observations.”
This idea that evidence of aliens may be flying through space and landing on unsuspecting planets, like Earth, is called panspermia. This theory is not incredibly popular with researchers, Totani admits.
However, this may be due in part to researchers believing that alien biomaterial could not survive either the radiation of open space or the heat of reentry into a planet’s atmosphere. But for the purposes of simply identifying that alien life exists at all, Totani writes that living aliens are not a prerequisite.
“My impression is that panspermia within the Solar system may be possible, because we know that meteorites from Mars are found on Earth,” Totani said. “However, it is not necessary to explain the origin of life on Earth.”
As for how researchers would even begin to identify these tiny dust particles, that’s where things get tricky. In his paper, Totani proposes two different approaches: collecting the dust in space before it reaches Earth or probing places on Earth where these particles might have been preserved, such as Antarctic ice or under the seafloor.
While the second option may be easier in terms of accessibility, differentiating alien biosignatures from those native to Earth won’t be an easy task. Likewise, catching these particles in space will require wider scale infrastructure than currently exists, although NASA has successfully demonstrated a smaller scale approach to collecting comet dust in space.
Either way, researchers may be stuck between a space rock and a hard place.
“In principle, compositions and isotopic ratios totally different from Earth grains, or microfossils totally different from life on Earth, may be useful to distinguish,” Totani said. “But ultimately, a better way is to collect such grains by detectors placed in space.”
As it stands now, this approach is still only a “rough theoretical idea,” Totani said. Before any decisions are made about which approach may be more feasible or advantageous, he said there will need to be discussion amongst other experts in the field to determine if this idea is worth pursuing.
