It seems like every few days, we hear about the discovery of another planet around a distant star. I think it’s great that we’re finding so many planets “out there”. It means that our solar system isn’t the only one in the galaxy (or in the universe, for that matter).

Implicit in the search for other planets is the search for life in the universe. Life, in other words, besides ourselves and the species that populate our planet. Astrobiologists (the scientists who study life and its possibilities on other worlds) are looking for conditions for habitability elsewhere. Of course, habitability means different things to different life forms.

A place that supports human life, for example, might not be very hospitable to other life forms. We see that in our own oceans, by the way. Humans can’t live in them without special habitats or suits; and whales and other denizens of the sea can’t make it on the land. So, we have a fine example of habitability right here on Earth. The same will play out as we look at other planets in detail to figure out which life they can support, and which forms they can’t. And, that includes viruses, which may or may not be considered living things, but certainly have an effect on life. As we are learning this year.

Wafting Viruses on Earth

Viruses and bacteria have existed on Earth for a long time. They’re part of the inventory of Terran biological specimens, along with planets and animals and humans. We’ve learned to live with most viruses and bacteria, even as we’ve developed medicines to help fight off their effects in humans. I say “most” because right now, we’re still struggling with the “fighting off the effects of” SARS-CoV-2, which is infecting large parts of the world right now.

I‘ve written about this virus from a science-fiction standpoint, but there’s nothing SF about its effects on humans. We don’t have a medicine or a vaccine that’s 100 percent effective.

Yet.

All we have at the moment are recommendations for mask-wearing, hand-washing, and social-distancing. Those, if taken all together, can and do help prevent the spread of the virus human-to-human. In places where these directives have been followed, transmission does eventually slow down. In places where people insist on gathering mask-free, having physical contact, and not washing their hands—well, the results are devastatingly tragic.

Part of the discussion about the COVID-19 disease focuses on how easily the virus travels between us. People know and accept (or they should) that the virus can travel through the air on sneezes and coughs. We know this from how easily colds and flu spread. The droplets we emit can carry viruses and bacteria. Viruses themselves can get caught up on the breezes, and ride the air. That’s why the common separation between people to help avoid catching the virus is six feet (just under two meters). Personally, I think it should be more.

Of course, viruses and bacteria ride the winds around our planet all the time. This is in addition to hitching a ride with animals and people. That’s true not just of the coronavirus we’re fighting now, but many others. I read a study the other day, describing the scientific measurement of the troposphere of our planet (just below the stratosphere). Researchers found viruses riding along on air currents there, on captured soil particles, and droplets of water from the ocean (whipped up into sea spray).

If and when all this viral load falls to the ground (as it eventually does), each square meter of the planet’s surface can be covered by hundreds of millions of viruses, as well as bacteria. (Want to know more about the study? Check out this 2018 study from the University of British Columbia.) So, viruses are a part of the inventory of “things” on this planet. They’re part of what we live with on Earth.

Viruses in Space

So, could viruses arise on other planets? Travel through interstellar space? Sure. I mean, it seems that if the ingredients for life are on those planets (the chemical precursors, water, warmth, something for them to latch onto), then yes, they could be on distant worlds. And, there are most certainly mechanisms to carry them from world to world in a planetary system (collisions sending rocks from one world out to orbit and eventual capture by another planet, for example).

Viruses aren’t necessarily considered to be life forms by biologists, although there’s a lot of debate about that. One thing they can agree on is that a virus is an infectious agent. Take SARS-CoV-2, which is causing so much trouble. It’s basically a bundle of RNA (genetic material) wrapped up in a bag of protein. (Note that some viruses consist of bundles of DNA, too, all wrapped up in a delivery envelope.) The SARS-CoV-2 bundle is, itself, encapsulated inside a lipid coat. Lipids are the basis of fats. Our little fiend also has little spikes protruding out from itself that help it “stick” to cells inside our bodies. Once inside a person, the virus injects its stuff inside of healthy cells, which then help it replicate itself inside the body. Mayhem ensues.

That sounds like vicious life form, but there’s no evidence that the virus itself is alive in any sense that we understand “life”. Some scientists think they ARE life because they carry genetic information and they reproduce, but others don’t accept them as life because of the lack of cellular structures inside the lipid shells. No matter — they exist on this planet and have done so from earliest history. In the grand scheme of things, there are helpful viruses that have evolved, and there are the unhelpful ones — like COVID-19. And, they came about using the same materials on the early Earth that helped form life. And, if they form here from our chemical element “load”, then they can likely do it elsewhere in the solar system and beyond.

Viruses in the Great Beyond

When we get around to thoroughly exploring planets (in person, for example) in the future, tests for life should include the search for viruses and bacteria. Sampling a planet’s chemical abundances on the surface, in the atmosphere, and in any bodies of water, will be necessary in the search for viruses, bacteria, and complex life forms. That’s only common sense. We have no way of knowing if an alien virus is harmFUL or harmLESS to human life. It’s a rough chance to take in exploration. We have the SARs-CoV-2 to thank for showing us that viruses new to humans can play nasty with our systems. Humanity is learning that lesson now, as we see how different people react to the virus; some get very, very ill (and die), while others suffer flu symptoms, and still others don’t even know they have it.

When our intrepid explorers head to Mars, for example, they should search for evidence of things that could have formed viruses in the past. Granted, the surface may be completely sterile, thanks to continual bombardment by solar ultraviolet radiation, but that’s not the only place where evidence lies. Digging beneath the surface will uncover further evidence, if it exists, of Martian viral forms. And, maybe, bacteria, too.

The same will be true of other places in the solar system, and beyond. Viruses, as we have learned from virology studies, are tenacious, opportunitistic agents. The quick spread of the COVID-19 disease proves that. Despite its size, it can teach a lesson to us about itself, and about what we must do to avoid the worst effects of this virus, and its possible cosmic cousins.