Can Viruses Travel Between Planets?

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 cov2 the virus that causes covid19 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 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 rna-based viruses in particular may have emerged from the pre-cellular rna world which would make them our most distant cousins on the tree of life or the tree of life and pushing their gene transferring powers that far back means they may have massively accelerated the evolution that led to the development from rna-based pseudolife to the first true dna-based cellular life understanding viruses may be the key to understanding the origin of life the extreme abundance of viruses on earth and their critical role in evolution and possibly even in abiogenesis suggests that we probably should be thinking about whether there are viruses on other worlds one of the most promising prospects for our first detection of alien life is to find signatures of its chemical activity in the atmospheres of alien worlds now we've talked about how this is done before but in short when an alien world passes in front of its home star we can see signature frequencies plucked from the starlight due to that light passing through the planet's atmosphere cellular life massively alters the atmosphere because it excretes gases oxygen methane nitrous oxide as that life metabolizes but viruses don't metabolize so won't leave direct atmospheric biosignatures but what about finding viruses in alien rocks that fall to earth well because viruses are so tiny they aren't likely to leave distinguishable fossils like bacteria can nor do they leave biosignatures in those rocks that means the remnants of dead viruses are unlikely to be found in meteorites from other worlds so the evidence of alien viruses is unlikely to come to us we'll probably have to go out to look for it the first stop in our search for life is always mars the red planet seems pretty dead these days but it's conceivable that an ecosystem of extremely hardy microbes lives beneath the martian surface and some viruses are among the hardiest of all microbes so it might pay to look for the signatures of viruses as we continue to explore mars perhaps more promising are the ocean moons of the gas giants jupiter's europa and saturn's enceladus these are known to harbor vast oceans beneath their icy surfaces oceans kept warm by the tidal flexing caused by their parent gas giants if those oceans contain microbial life then they may also contain viruses both europa and enceladus spray geysers of ocean water into space that can be captured by probes specialized instruments on future missions could detect viral material okay all of this talk of viruses hitching right into space brings us to our last most sci-fi horror movie relevant point can viruses from one planet infect another there are two parts to this question can a virion survive an interplanetary journey and then can it actually do anything when it arrives the answer to the first part is definitely sort of maybe like i said viruses can be carried by tiny water droplets earth's upper atmosphere is thick with bacteria and viruses mostly swept into the atmosphere from the oceans by sea spray from there they can travel across the globe but also perhaps be lifted into space very light droplets can be lifted to the very edge of an atmosphere with the help of its planet's magnetic field and then swept into interplanetary or even interstellar space by the radiation from the star this is radio panspermia and it's a compelling way to transport viruses because the mechanism is especially effective for very small water droplets of the kind that viruses tend to occupy in fact it will be surprising if there were not quite a lot of viral and other microbial material riding the solar wind into interstellar space so yes stars sneeze you might want to maintain that six light-years distance viruses can also be launched into space embedded in rocks that are ejected in asteroid or comet impacts this is lithopanspermia and again virus-ridden rocks have definitely left the earth before and probably impacted other bodies in our solar system earth certainly gets hit by rocks from mars so if mars ever had viruses then some of that material may have reached earth virus bearing rocks from worlds beyond our solar system are possible but those viruses would need to remain viable for hundreds of thousands to millions of years and it's the ability of viruses to survive long space flight that becomes the real question outer space is deadly it's a freezing cold vacuum bathed in intense radiation virions are a bit like seeds or spores dormant until they come into contact with their prey and like seeds or spores some virions are remarkably resilient take the tobacco mosaic virus it can actually be crystallized protecting it from desiccation cold and vacuum in fact that particular virus has survived being bathed in the equivalent of 250 years of cosmic rays simulated by an intense shower of energetic protons the poliovirus and bacteriophages have stayed infectious after space-like environments of high-altitude balloon and rocket rides some bacteriophages have also shown resistance to ultraviolet exposure in experiments on the international space station however their viability after that exposure hasn't been tested some viruses do have the remarkable ability to sort of reassemble their genetic code after a radiation by uv or cosmic rays even if most individuals within an infecting population have damaged genes as long as the full correct virus genome is represented across the population within a given infected cell the viral genome can be reconstructed as the virus replicates itself all of that said radiation from stars is probably our best hope for obliterating space viruses beyond a certain point a damaged genome renders a virus non-functional and can't be reconstructed it's likely that uv exposure would destroy most viruses trying to hitch rides via radio panspermia and that's good because that's the only known way to really spread lots of viruses between planetary systems lithopanspermia can spread vastly fewer microbes but it's more reliable because a barrier of rock or ice will shield against ultraviolet light and cosmic rays okay so we've established that there's at least a remote chance of interplanetary or even interstellar viruses making their way to earth or earth viruses going back the other way but are such alien lurgies really a possible danger in order for a virus to infect a cell the virus needs to bind with receptors on that cell surface and then integrate its genome into the cell's dna different viruses have evolved to infect a vast array of different cells and some even infect other viruses but one thing they all have in common is that viruses all infect life as we know it at the very minimum a cell needs to be dna or rna-based to be susceptible to earth viruses would alien viruses have evolved to attack the same genetic structure that would only be the case if dna rna-based life was the norm for extraterrestrial life and we have no idea whether that's the case perhaps dna is the only possible basis for complex life or perhaps panspermia seeded dna based life and dna praying viruses across the galaxy but it's very likely that an alien virus that made its way to earth would find it had absolutely no way to attack the cells it finds here let's get to the last pressing question which is also the easiest could any of the past recent pandemics have resulted from alien viruses no we can trace the origins of viruses by their genes take the sars curvy two virus it shares the overwhelming majority of its genes with coronaviruses found in populations of horseshoe bats and the phylogenyx the evolutionary path is consistent with it evolving out of that population same with other epidemic causing viruses like ebola and the spanish flu it's never aliens if there's a sensible earthly explanation but like i said this is an astrophysics show so i'll add some links for more expert analysis of the virology in the description in the meantime please stay safe from the current very terrestrial virus outbreak and at least appreciate this we are now much more aware of the importance and danger of a hidden world that has always lived alongside us driven our evolution and perhaps predated life itself the world of viruses our currently not so favorite but still fascinating fellow denizen of space time last time we explored the possibility that the existence of extra hidden dimensions might change the law of gravity on the smaller scales and we saw how the 120 year old cavendish experiment might reveal those dimensions long story short it hasn't yet but the search continues kronoslav asks how we can know the inverse square law for gravity holds on cosmic scales if we haven't explained dark matter yet which originated from the apparent failure of the inverse square law in the first place in other words maybe the inverse square law breaks down on large scales producing the illusion of dark matter so people have investigated this in great detail actually the theory is modified newtonian dynamics mons in which gravity doesn't drop off as quickly as the inverse wheel or when you get to very large distances two issues with this idea mons fails to get rid of the need for all dark matter some invisible mass is still needed and so that kind of eliminates a lot of the elegance of the idea second we have other evidence of dark matter for example in gravitational lensing in the cosmic microwave background speckles and in things like the bullet cluster where it seems that the dark matter is separated from the stars and therefore can't be due to just having the wrong theory of gravity now a few of you had a really interesting insight i said that when the masses of the cavendish experiment are very close together you need to factor in the casimir force between them to get an accurate measurement for the gravitational force so what if the casimir force itself is a modification of the gravitational force on tiny scales well the casimir effect is thought to be due to an alteration in the vacuum energy between a pair of conducting surfaces which leads to those surfaces being attracted to each other so why couldn't it be an increase in the strength of gravity well it's because you would then expect experiments to measure a casimir force that has a simple dependency on the mass of the two plates and their separation but that's not the case the casimir effect depends strongly on the material of those plates its conductive and its dielectric properties as well as the geometry of the plates and for the most part that dependency agrees with the so-called lift sheets theory which is based on this altered vacuum energy hypothesis castle night 7 asserts that gravity as with all forces is created by consciousness well i'd accuse you of propagating quantum woo except that this theory is actually supported right at the top the experimental physicist wiley coyote demonstrated this on multiple occasions and i believe it was the great douglas adams that had a similar hypothesis remember in one of the later hitchhikers guide books when arthur dent figures out the secret to flying is to throw yourself at the ground and at the last minute get distracted and miss i believe the full theoretical framework was published in the eminent science journal the onion it's a refutation of mainstream gravity called intelligent falling you

Channel: PBS Space Time

Views: 357,522

Keywords: Space, Outer Space, Physics, Astrophysics, Quantum Mechanics, Space Physics, PBS, Space Time, Time, PBS Space Time, Matt O’Dowd, Astrobiology, Einstein, Einsteinian Physics, General Relativity, Special Relativity, Dark Energy, Dark Matter, Black Holes, The Universe, Math, Science Fiction, Calculus, Maths, astrovirology, COVID 19, COVID, coronavirus, sars cov 2, covid 19 news, virology, virus, viruses

Id: o2ZcvPW5EcI

Length: 17min 9sec (1029 seconds)

Published: Mon Jun 08 2020

Reddit Comments

[u/mrmonkeybat]

He seems to be saying that viruses can exist before cellular life or without it, but viruses depend on cellular life to carry out their reproduction for them.