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Cosmic Driftwood

In late October, our Solar System received an alien visitor.
A triangular sci-fi spacecraft hovers over the ocean while a humpback whale is lifted out of it in a beam of white light. Text: Our alien guest wasn’t a spaceship or robotic probe looking for humpback whales.
In outer space with the earth in the background, a small gray sliver catches the light of the sun. Text: Instead, it was an asteroid the size of a building. An entirely natural bit of cosmic flotsam from another star system.
A close up of the sliver shows it to be a 20m wide, 200m long asteroid that is gray with a reddish hue on one end of it. Text: Astronomers called it ‘Oumuamua, and it’s the first asteroid we’ve ever seen that didn’t form in the Solar System. Its name is from the Hawaiian language, meaning roughly, “first messenger”.
In a stylized map of our solar system with the planetary orbits represented with white lines, a gold colored line traces a path through the center of the disk, bends around the sun, and shoots out of the bottom of the frame. Text: We don’t know precisely where ‘Oumuamua came from, only that it visited us for a brief moment in time before moving on to the emptiness of interstellar space. And we know this isn’t the last time we’ll receive such a guest.
How do we know that ‘Oumuamua didn’t originate in the Solar System?
The Earth and the asteroid, both with drag racing tires and fins, trail smoke behind them as they rocket around a circular path at 30kps and 26kps respectively. Text: When astronomers first saw it on October 19, 2017, ‘Oumuamua was traveling at an astoundingly fast 26 kilometers per second – 58,000 miles per hour. Observing it over the next few days, they calculated its trajectory, and found it was following a hyperbolic orbit. But it’s not a spaceship.
The asteroid car careens off the path and falls into the blackness of space. Text: Planets, asteroids, and comets follow nearly perfect elliptical orbits around the Sun. ‘Oumuamua zoomed into the Solar System and right back out again. That means it had to have come from the expanse of interstellar space.
Text: If it wasn’t for its freaky drive-by orbit, ‘Oumuamua wouldn’t stand out. Michele Bannister, of Queen’s University Belfast stands in front of an observatory and explains. She is a white woman with auburn hair wearing rectangular glasses and a red hoodie. Text: We know what the reflectance spectra of spacecraft look like, because people have measured that for a lot of spacecraft around Earth: it doesn't look like that! lt looks a lot like groups of asteroids you see in the outer part of the asteroid belt.
Another view of 'Oumuamua, surrounded by question marks. Text: ‘Oumuamua also doesn’t resemble the inhabitants of the far outer Solar System.
Pluto and Sedna in natural sunlight, painted in brilliant reds and blues, their dark sides disappearing into the black. Text: It’s not “ultra red”, like some of the splotches on Pluto or like the weird iceball Sedna.
A white craggy chunk of ice, trailing dust and gas behind it. Text: I doesn’t have ice or gunky organic molecules, like comets do. Everything points to it being an asteroid from a star system far away.
So why was it here? And why haven’t we seen anything like ‘Oumuamua before?
In a dramatic depiction of the birth of a solar system, a hot white star is surrounded by light brown clouds of dust. Larger objects in orbit around the star carve paths through the dust and cast long shadows across the rings. In the foreground, the dust can be seen as large clouds and harshly lit asteroids. Text: Star systems begin when gravity collapses clouds of gas. As they condense, they spin into thick disks. Inside those disks, molecules clump together like cosmic dust bunnies, forming chunks of rock called planetesimals. The big chunks grow into planets, while smaller fragments are asteroids, comets, and other small bodies. But newborn star systems also shed a lot of planetesimals out into interstellar space. ’Oumuamua is probably one of those.
One of these craggy rocks is seen above a blue earth-like world. Text: That means planetesimals from our newborn Solar System could be passing through other star systems. But it also means ’Oumuamua wasn’t our first interstellar visitor, and won’t be the last.
David Grinspoon of the Planetary Science Institute, a dark haired white man with thick round frames, a goatee, and a black fedora explains: Text: If there are many ’Oumuamuas, which it seems there must be, then some of them will shed some material as they fly through our system.
A stylized top-down view of Saturn and its rings with one of its orbiting moons highlighted in blue. Text: Because of its weird orbit and chemistry, scientists actually think Saturn’s moon Phoebe originated in the outermost Solar System. Inset Image: A blonde bearded man in a porkpie hat and a trenchcoat (representing the writer Matthew Francis as Expanse detective Josephus Miller) walks past a window where a rocky landscape and Saturn can be seen looming on the horizon. Text: In the TV show and book series, The Expanse, Phoebe was a vehicle to transfer alien molecules from their star system to ours.
From a distant solar system, three colored streaks of green, blue, and red strike planets in the foreground. From the impacts, forests and cities sprout up. Text: Outside of science fiction, some scientists have entertained a theory called “panspermia”, where life originates elsewhere in the cosmos and spreads from star system to star system.
Back in space, a comet and 'Oumuamua fly side by side. The comet is trailing dust that scatters atoms and molecules such as water, amino acids, hydrogen, oxygen, and carbon. The latter object just has a question mark coming off of it. Text: ’Oumuamua didn’t exhibit the complex organic molecules we see on comets, much less the even more complicated molecules of life. But it’s possible some chemistry required for life as we know it might travel between star systems.
Text: But life itself? ’Oumuamua was likely traveling for hundreds of millions of years at minimum before it got to us. David Grinspoon is seen in profile in front of the visiting asteroid. A magnified view of the rock's surface shows a dead tardigrade with a comical green skull above it. He explains: The best argument against panspermia is that organisms, even in dormant form, might not be able to survive the very long journey of an interstellar comet or asteroid between star systems.
A white line traces a path that bends around several kinds of stars, large blue binary systems, a smaller yellow sun, and an old red star with active flares. Text: Since ’Oumuamua looks very much like a Solar System asteroid, it tells us that the chemistry of its original star system is probably similar to others.
The path weaves its way around a myriad of hospitable planets, blue with water and showing continents and atmospheres similar to earth. Text: That means the stuff of life is likely common throughout the galaxy, whether panspermia is true or not.
Humans have watched the sky for thousands of years.
In a cartoon depiction of the Mayan civilization, two men look up at the stars depicted in the same way as in Mayan imagery as circles with four triangular points coming off of them. The sun is is similarly rendered as an image of the famous Mayan calendar. One of them men raises their arms to the sky while another takes notes on a clay tablet. Text: We learned the predictable dance of the Moon and planets, and described it in the languages of mathematics, poetry, and religion.
A stylized shooting star streaks through the sky with a skull at its center. The first man points angrily at the object which has interrupted their otherwise predictable sky while the other shrugs their shoulders in dismay. We also learned some things aren’t as predictable: meteors, comets, and maybe the occasional passing asteroid.
’Oumuamua drifts small and alone in the vast blackness of space. The sun is a tiny yellow dot in the background. Text: Space is big and mostly empty. Even places like our Solar System are more empty than not. ’Oumuamua is very small, and because it’s dark in color, we had to be looking in the right place at the right time.
Michele Bannister explains: You need to look at a lot of the sky, and you need to do it quite frequently. That's why in 19 years or thereabouts of digital sky surveying, this is the first one that we've seen.
On a rocky hill, a futuristic white building stands in stark contrast to its surroundings. Text: The Large Synoptic Survey Telescope (LSST), which is currently under construction in Chile, will likely see many ’Oumuamuas every year.
A realistic painting of Saturn and its moons seen from above. The gas giant casts a long shadow across its rings. In the foreground, an out of place piece of driftwood floats by. Text: Bannister thinks of ’Oumuamua as a piece of cosmic driftwood that happened to bump into our Solar System as we passed. “The thing that driftwood tells us is that there are trees on distant shores.” One ’Oumuamua tells us there are asteroids in far-flung star systems.
In another scene depicting an early solar system, the area around the star has been mostly cleared out save for a cloudy ring. The viewer is positioned inside this ring, which is shown to be made up of countless asteroids. Text: Many ’Oumuamuas will reveal more about how those star systems formed, and something about their chemistry, their history...
...and maybe...
Within a dusty orange clouds, an earth-like planet begins to rise, it's wispy cloudy atmosphere partially obscuring its deep blue oceans and green continents. Text: ...the chances of life elsewhere in the galaxy.

Description

In 2017, we were visited by an object from outside our solar system--an asteroid. In this comic, scientists tell us how this piece of cosmic driftwood got here and what it might be able to tell us about the distant shores in which it originated.

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