What do you think of when you hear the word ‘asteroid’? We tend to relate it to monumental
disasters and massive doomsday scenarios. For whatever reason, it’s as though these giant space
rocks are solely out to get us. And, really, there is some truth in that, as asteroids certainly can
be dangerous, and impacts definitely can be life-threatening. However, there’s research to
turn those ideas totally around. Asteroids may be synonymous with widespread death and destruction,
but scientists also propose that they’re vital for the emergence of life itself, as well.
This is Unveiled, and today we’re answering the extraordinary question;
is there alien life hiding in the asteroid belt?
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Asteroids are rocky objects, ranging in size from just a few feet across to hundreds of miles
wide. They, like everything else in the solar system, revolve around the sun. The larger ones
are sometimes alternatively known as planetoids… while more than one million asteroids (in general)
have been identified so far, according to NASA. Some of those have already struck our planet,
with impacts of varying severity happening throughout history… while many more are possibly
on a path to collide with Earth in the future. First and foremost, it is for this reason - to
try and keep across what might (or might not) happen - that astronomers eagerly study asteroids,
in the first place. They’re keen to learn about their orbits and physical characteristics,
and whether or not we should ever be especially concerned about any one asteroid, in particular.
But despite the danger they pose, opinions aren’t all bad regarding these enigmatic space
rocks. Although, for many decades, scientists believed that asteroid impacts may have hindered
the emergence of life on Earth… that view has been set aside more recently, with many now
suggesting that crashing asteroids could have instead played a crucial role in the formation
of life, by providing various deliverables essential for the chemistry of living things.
These deliverables may have been in the form of new habitats that an impact crater creates,
spawning lakes, as well as regions of lower and higher altitude. Or, more significantly still,
it’s thought that past asteroids may have brought water to the surface of the Earth,
probably the most important single substance of all. It’s believed that asteroid events
have helped to shape the atmosphere of our world, too, sparking and nurturing the growth of complex
organic molecules within. Impact craters may have provided some shelter against ultraviolet
radiation from the sun before then, as well, while the atmosphere was forming. Asteroid impacts, such
as the Chicxulub event which led to the extinction of dinosaurs, are also known to have helped create
hydrothermal vents, which work a little like a plumbing system to help drive Earth’s own
evolution forward. And contemporary views consider these vents to be of massive importance. Theories
are that, over many millions of years, they have helped to transport heat and chemicals
from our planet’s interior to the surface and in doing so regulate the chemistry of our oceans.
The resulting accumulation of minerals on the seafloor, then, again over millions of years, has
helped to promote life on our planet and guide the important transition from chemistry to biology.
Enter Drs. Rebecca Martin and Mario Livio at the University of Nevada’s Department of
Physics and Astronomy. In 2022, they released a draft paper titled; “Asteroids and life:
How special is the solar system?”. Through it, the authors suggest that asteroid impacts on a
terrestrial planet may be a necessary condition for life. And then, if asteroids are essential,
then asteroid belts might also be just as vital for life to emerge in a star system. While it
appears that in ours - the solar system - the belt between Mars and Jupiter will have played a key
role, could it be the same in other exoplanetary systems, too? These systems beyond our own would
then also require similar mechanisms to what we have, to drive asteroids out of the belt
and toward any potentially habitable worlds. To bombard the surfaces of planets that lie within
the Goldilocks zone of an alien sun, and in doing so potentially seed them with life.
This realization has important implications, then, in our wider search for alien life.
The main takeaway is that if we want to find alien life in the universe,
we should perhaps begin by looking for stars that specifically host systems with asteroid
belts - like the one in our own neighborhood. For example, we know that our belt hosts
millions of asteroids… so it would make sense to target a similarly well-populated alien belt,
too. The origin of our belt is tied up with the formation of the solar system itself,
as bits of dust and rock that weren’t incorporated into the creation of planets settled instead
to become the asteroid belt. Again, if the importance of the belt is correct,
then we’d perhaps be best served searching for a star system with a similar backstory to our own.
The mechanisms to drive asteroids out are a little more difficult to determine. But,
there are at least two theories - called the Nice Model and the Grand Tack - to suggest
that the regular and periodic influence of giant planets (such as Jupiter and Saturn,
in our case) is what’s crucial. It’s thought that the presence and influence of the gas giants
has continually disturbed the asteroid belt over time, which is why rocks have
fallen out and toward the sun, occasionally crashing into the inner planets, like Earth,
as they go. Similar disturbances are thought to restore the belt, over time, too… so that Jupiter
and Saturn act something like gatekeepers for the belt, regulating what goes out and what comes in.
With this important connection in mind, Martin and Livio, as part of their 2022 study,
considered its consequences in three separate simulations… each running a different arrangement
of giant planets in our solar system, with the Earth in its present orbit. Amazingly,
the simulations demonstrated that Earth faced the highest number of asteroid impacts in the current
configuration of the solar system. One alternative arrangement had one of the giant planets take
twice as long to orbit the sun as the other, which resulted in far more asteroids being ejected from
the belt but with lesser impact events on Earth. Meanwhile, in the other alternative,
where the second giant planet was removed completely, impact events on Earth were even
further reduced. The finding, then, seemingly supported the idea that an asteroid belt (and
wider solar system) as close to ours as possible would equal the best bet for alien life elsewhere.
To back their simulations, Martin and Livio examined NASA’s exoplanet archive - detailing
planets beyond the solar system. While some are rogue planets - free-floating worlds that
orbit galactic centers rather than a star - most exoplanets we know of do circle stars,
and many that are much like our sun. For further research, these were the ones that were of most
interest. Digging deeper into the specifics, the authors focused on systems with two known
giant planets… and especially when those giants were found at similar distances away from their
host star, as Jupiter and Saturn are from the sun. This is a challenging task as exoplanetary
detection of massive planets in wide orbits is quite difficult. Among the candidate systems that
Martin and Livio identified, four of them seemingly had just the right arrangement;
that is, an arrangement to support the correct disturbance of asteroids out of
the belts and to provide for the emergence of life, according to their hypothesis.
In essence, as per their hypothesis, the search for extraterrestrial intelligence had,
on the one hand, suddenly gotten a lot harder because it was much more specific… but, also,
on the other hand, gotten much more nuanced and informed. A habitable
world in the habitable zone is, perhaps, no longer enough. Neither is a sun-like star,
alone. This work suggests that there should also be similar giant planets to those that we have,
positioned at similar distances… and that those giants should similarly regulate a
comparable asteroid belt, to provide all the earliest events and building blocks for life.
That might all feel like a lot to ask, but the authors arrive at a somewhat
optimistic conclusion, highlighting that; “the solar system is somewhat special,
but the degree of fine-tuning that may be necessary for the emergence of life is
not excessive”. Presumably meaning that, in their view, it could happen again. And now,
if we follow this line of thinking, we could be better prepared than ever to find it.
That said, and despite these intriguing results, Martin and Livio also concede that the fact that
this model is largely based on the classical picture of solar system formation could yet
hold it back. The story of creation may not be the same in other solar neighborhoods in space…
there could be other events and mechanisms at play that we can’t really comprehend.
Nevertheless, what are your thoughts on the potential importance of this
new way of looking at distant planetary systems? For now, there is, of course,
still so much we still don’t know about the universe… but that’s why alien life
could yet be hiding in the asteroid belt. Or another asteroid belt, elsewhere, at least!
What do you think? Is there anything we missed? Let us know in the comments, check out these other
clips from Unveiled, and make sure you subscribe and ring the bell for our latest content.