Alien life may thrive in space dust released by huge asteroid impacts

The size of this material will vary widely, and different-sized pieces will behave differently in space.

Some larger fragments might re-fall or go into a stable orbit around a nearby planet or star. Smaller ones might be too minuscule to contain any observable indications of life. 

Yet, grains smaller than one micrometer (one-thousandth of a millimeter) can not only contain a single-celled organism specimen but also to completely escape their home solar system and, under the appropriate conditions, perhaps even flee to ours.

"My paper explores this idea using available data on the different aspects of this scenario," stated Totani. 

He noted, however, that the travel times and distances can be extremely long. Both lower the chance that any ejecta carrying indications of life from distant planets will ever reach us. 

Additionally, the odds become significantly lower when factoring in the numerous space phenomena that can potentially melt or irradiate tiny particles. 

"Despite that, I calculate around 100,000 such grains could be landing on Earth every year. Given there are many unknowns involved, this estimate could be too high or too low, but the means to explore it already exist, so it seems like a worthwhile pursuit," he reasoned. 

Better yet, Totani highlighted that these grains might already exist on Earth, preserved in large quantities in areas like the Antarctic ice or beneath the seafloor. And if so, Space dust in these locations might be relatively straightforward to recover.

Still, it's challenging to tell extrasolar material from that originating from our own world. 

But what if the search is extended to space itself? After all, there are existing missions that use ultralight materials called aerogels to gather dust in a vacuum.

"I hope that researchers in different fields are interested in this idea and start to examine the feasibility of this new search for extrasolar life in more detail," concluded Totani.

The full study was published in the International Journal of Astrobiology on March 22 and can be found here. 

Study abstract:

Searching for extrasolar biosignatures is important to understand life on Earth and its origin. Astronomical observations of exoplanets may find such signatures, but it is difficult and may be impossible to claim unambiguous detection of life by remote sensing of exoplanet atmospheres. Here, another approach is considered: collecting grains ejected by asteroid impacts from exoplanets in the Milky Way and then traveling to the Solar System. The optimal grain size for this purpose is around 1 μm, and though uncertainty is large, about 105 such grains are expected to be accreting on Earth every year, which may contain biosignatures of life that existed on their home planets. These grains may be collected by detectors placed in space, or extracted from Antarctic ice or deep-sea sediments, depending on future technological developments.