Can Viruses Travel Between Planets?

**SPEAKER_1** (0:00)
This episode is brought to you by Accenture. When you're advertising operations fall out of sync, everything else follows. Spotify and Accenture are working together to reinvent the rhythm of ad sales. Using automation, analytics, and smarter workflows to simplify campaign delivery and access better data across the business. The result? Less time spent on operations, more time connecting brands with the moments and fandoms that matter most. Learn more at accenture.com/spotify.

**SPEAKER_2** (0:30)
Your new hair era is here. At Sephora, you'll find carefully selected hair care products that work for your hair and take it to the next level. Your search for dream hair is over. Sephora is the place for hair care. Discover the best products that give your hair the treatment it needs from brands like Kerastase, K18, and Gisu. Plus, with free shipping and same day delivery, there's never been a better time to trade up to healthier looking hair.
Shop hair at Sephora.

**Matt O'Dowd** (1:00)
We are generally not big fans of viruses right now, but we sure are thinking about them a lot. That's right, even astrophysicists are pondering these bizarre little critters. In fact, astrovirology, although very new, is actually an emerging subfield of astrobiology. And that's because it turns out that viruses don't just influence organisms. They're incredibly important on a planetary scale. Perhaps, an interplanetary scale.
There are more viruses on Earth than all cellular organisms combined. And so they drastically affect our entire biosphere. And it's increasingly believed that viruses are critical factors in the process of evolution, perhaps even in pre-cellular days. That's right, viruses or their ancestors may have played a role in the origin of life on Earth, and may be needed to initiate life on any planet. Oh, and astrovirology is also concerned with the possibility that viruses can travel between worlds. I'm going to start with this absolute statement because you know how the internet can be. The new coronavirus, SARS-CoV-2, the virus that causes COVID-19, did absolutely not fall to Earth from space. I'll come back to how we can be 100% confident of that a bit later.
First up, let's talk viruses generally. But let me preface this by stating the obvious. Astrophysics channels are not the best place to learn virology. I want to do this review to highlight the details of viruses that make them important on planetary and even interplanetary scales. Viruses sit on the blurred line between living and not. They contain genetic material, either single strand RNA or double strand DNA, and when not active inside an infected cell, they surround themselves in a protein shell, a capsid. We often think of a virus as this bundle of genetic material within a shell. But the term for that bundle is a virion, and this is more of a transport mechanism for the genetic material. The term virus better describes the entire microbial life cycle, and inside an infected cell, the virus has no shell. It is the genetic material.
Unlike cells, viruses do not metabolize, so they don't produce their own energy, and they can't reproduce without co-opting the reproduction machinery of a cell, hence the dispute over whether they can be called alive.
One thing viruses do share in common with life is the ability to evolve. Their extreme numbers and reproduction rate means rapid evolution. As well as resulting in the vast array of existing viruses, this means some viruses produce new strains every year. That's why you need a new flu shot.

**SPEAKER_4** (4:02)
Back to school is busy enough. The last thing you need is shopping that makes it harder. Whether you're moving into a dorm, your first apartment, or just getting organized for the semester, Wayfair makes it easy to get everything you need in one place. Furniture, bedding, storage, decor, study essentials, all at prices you'll love, with fast shipping before move-in day.
Get everything you need for back to school season. Shop wayfair.com today.

**SPEAKER_1** (4:28)
Wayfair, every style, every home.

**SPEAKER_5** (4:31)
This is a Bose moment. It's 10 blocks from the train to your apartment door. 10 basic, boring city blocks until the beat drops in Bose clarity.
Streetlights become spotlights as you strut down the sidewalk, your own personal runway. With Bose you get every note, every baseline, every detail just as you should. Those 10 blocks, they could be the best part of your day.
Your life deserves music. Your music deserves Bose. Find your perfect product at bose.com.

**Matt O'Dowd** (5:00)
Each season. But viruses aren't just masters of their own evolution. It seems they may be an essential driver of the evolution of cell-based life. Because viruses insert themselves into DNA to reproduce, they're actually able to transfer genes between organisms. Viruses are the original genetic engineers, and some of your most useful genes were left in your DNA by a virus that infected an ancestor. As well as driving cellular evolution, viruses may have been critical in the formation of cells in the first place. For a long time, it was believed that viruses evolved as escapees from DNA-based cells, but more and more virologists think that viruses may predate cells.