If life doesn't always show up on planets that can support it, what will happen? Is it possible that we find more and more exoplanets that are in the right place? Life hasn't appeared on them yet, what if that's the case?
Is it possible to bring comets to those planets and give them life? Shouldn't we do that?
This is the topic of a new research article. The paper is called directed panspermia using interstellar comets Christopher P. McKay, Paul C.W. Davies, and Simon P. Worden wrote the book. The Beyond Center for Fundamental Concepts in Science at Arizona State University is from NASA.
Panspermia is a belief that life can spread throughout the universe. Pan and sperma are ancient Greek words. This is not a new idea. Anaxagoras was the first to propose it. He mentioned that seeds could be part of the universe. Historians put two and two together to make sense of what he said. According to panspermia, life was spread by asteroids, comets, and even space dust.
Impacts on planets like Earth or Mars could cause rocks to fly into the air. Impacts on Mars have sent rock into space. Over 200 of them have been found on the planet. It would have happened in other systems since it happened on Mars.
Billions of years ago, we believe Mars was inhabited by organisms. It is possible that the Martian microbes hitched a ride on impact-ejected rocks and were protected from the dangers of space. Life could theoretically spread if the rock crashed into another body and the heat from the impact didn't wipe out any survivors. The panspermia idea starts to take shape when you take into account the number of solar system crashes in the Milky Way.
Panspermia is accidental or natural. It's called directed panspermia if a civilization did this on purpose. The paper is about the civilization.
We don't know how life got started. We know some of the conditions, but we don't have all the information. We don't know how it came to be on other worlds. The authors point out that they don't have a good idea of the appropriate geological/chemical setting for non life to transform into life.
We believe life may exist elsewhere. We don't know if all planets have life on them. There is a chance that a favorable location for life's origin is different from a planetary environment in which life might be successfully sustained over the long term.
The question of how life began isn't addressed by Panspermia. It asks us to think about how life could spread from one world to another in the universe. Around 200 billion stars make up the Milky Way. There are lots of solar systems, planets, asteroid belts, and Oort Clouds. There are a lot of opportunities if panspermia occurs.
Each planet and moon is a part of the puzzle. Mars probably had life in the past, but not now, unless it is underground. Some of the icy moons have hospitable oceans under the ice caps. The only body other than Earth with liquid on its surface is Titan. There is a planet that isripples with life. I wonder if panspermia is the thread that connects all these pieces.
Life on Earth is one of the Solar System's puzzles. Life appeared on the young Earth. As far back as 3 billion years ago, cellular life may have existed. When Earth emerged from the Hadean eon, it was covered in a thick, carbon dioxide atmosphere and ruled by super-heated conditions.
After the Hadean, some scientists wondered how life could have appeared so quickly. The idea of panspermia is supported by this thinking. Panspermia may be able to support life on Earth and other young planets.
The panspermia idea has been elaborated in detail by modern thinking. We may be able to see all of the exoplanets in a 100 light year sphere. There is a proposal to send a spaceship to any planet that can hold life. Humans may have to wrestle with the idea more realistic in the future because time has a way of passing.
The authors think that this idea is doable. What about the cost? Is it related to spacecraft reliability?
Comets are capable of long voyages. They have become part of the discussion about directed panspermia. The idea of directed panspermia using comets is proposed in the article.
“Until recently, the idea that humans could literally sow the seeds of a cosmic transformation having multi-million-year downstream consequences would have been regarded as absurd. But the discovery of interstellar comets has changed all that.”
From “Directed Panspermia Using Interstellar Comets.”
Specific events from the last few years inspired the article. The solar system had an object pass through it. The comet 2I/Borisov visited our solar system two years later. Borisov is the first comet we have seen passing through our system. How many more ISOs will the same journey be?
The discovery of two ISOs in a short period of time is a result of technological advancement and a large number of telescopes. There were many other people in the Solar System, and there will be many more in the future. The authors think that they are common and present an opportunity.
Interstellar comets allow low-cost directed panspermia that is potentially wide in scope. According to the study, a total of 6.9 objects should pass within oneAU of the Sun. We will find these ISOs five per year when the Vera Rubin Observatory opens.
The authors find comet Borisov fascinating. Estimates put it as big as 16 km. It's large enough to protect it from radiation. It lost mass as it traveled through the inner Solar System. They say that the dust it left behind can be used to spread information.
The authors explain how comets can spread life. Natural and directed panspermia would be combined by ISO. Adding biological inoculum to a comet without attempting to change it's trajectory is how it combines them.
A collection of life forms that can successfully seed different habitats on different planets is the ideal inoculum. The authors say that liquid water on the surface of planets like Earth and early Mars could lead to diverse and complex life. Earthly methanogens may be the most appropriate inoculum for Enceladus.
Single-celled organisms aren't the only ones that can be found in the inoculum. In some instances, small multicellular organisms might be the best choice. Tardigrades are hardy and can survive in space.
Genetically-modified organisms could be involved in a program of panspermia. There are a lot of different worlds that are not like Earth. The best example might be Titan, because we have them in our solar system. There is only one body other than Earth with liquid. As synthetic biotechnology advances, we might be able to construct life forms that could thrive on Titan and in other non- water habitats discovered on exoplanets in the future.
“… merely dropping a few microbes on a habitable but otherwise barren planet would not successfully seed it.”
From “Directed Panspermia Using Interstellar Comets.”
The authors acknowledge that this could be a waste of time. Is it as easy as putting life forms on a planet? A serious argument that might be advanced against panspermia stems from the idea that life is a planetary phenomenon that forms a global web of interdependent organisms. Dropping a few microbes on a barren planet wouldn't succeed in seeding it.
It would need to be a custom design. It would need to be a web of its own, designed for a specific environment, that could successfully implement relationships between life forms. That is a challenge. It is a formidable challenge that may require significant advances in our understanding of the web of life.
When we imagine a future where all of this becomes possible, it's hard to see. We are going to explore some of Jupiter's icy moons soon, and a mission to Titan is likely to follow. Will we find anything? Will we be tempted if they are barren but have life-supporting qualities?
There are some uncomfortable questions. The consequences of using technology are more far-reaching when it becomes more powerful. People consider how they could go wrong as a result of technological advances. The concerns would carry over with a vengeance to the purpose of life in the universe.
Some will think that crazy scientists want to plow ahead and start messing with the whole universe. We are not close to doing any of this so we can pull ourselves back from the ledge.
There is a critical question about directed panspermia before we get to the questions of can we or should we. We don't know how many planets are capable of supporting life. Astrobiological optimists tend to think that the planets are likely to be inhabited. That is only a guess.
It is possible that a small percentage of the planets and moons have life on them. There are a billion or more planets that can support life, but natural panspermia hasn't reached them yet.
Since panspermia is a part of the Universe, we have a role to play in spreading life. We might have the duty to do so. It is possible that Earth was seeding by panspermia. It is possible that a long-dead civilization decided to face what we are facing now.
It is the nature of these questions to have a lot of possibilities. It's possible that this is how it goes for civilizations. The Kardashev Scale lays out the advanced types of civilization. There is a point where the Great Filter looms over all our affairs. When civilizations reach that point, they can't do anything else. It will take a long time before we understand what is going on in the universe.
There are a lot of possibilities strung together on an uncertain path. There are more than one string of possibilities that lead to caution when we follow them.
Is it possible to send life to a planet that is only at the beginning of its existence? Our good intentions might end in disaster if that planet's life is snuffed out by Terran life that is better than it.
We base our panspermia decisions on biosignatures, but our understanding of biosignatures may be biased towards Earth life. Our robust, genetically engineered microbes committed a uni-cellular atrocity and wiped out the planet's existing life
Our life-bearing comet could find an uninhabited target and successfully seed it with dust. If it didn't stop there, what about the other planets? Our good intentions can be seen as an invasion or a weapon.
The situation gets more complicated. We have questions about what happened on Earth.
Early Earth life was abundant for a long time before it died off. Complex life appeared and took over the planet as Oxygen became more concentrated in the atmosphere. If panspermia were used to seed the genetic ability to perform photosynthesis, what would it look like? If life never made the energy-exploiting jump to photosynthesis without a boost from panspermia, what would it look like?
We have a lot more to know about comets. There were several candidate missions that the ESA chose from. In 2029, they hope to launch it. The Sun-Earth L 2 point is where the Interceptor will sit and wait for a suitable long period comet. By 2029, we will have telescopes that can see comets before they reach the Solar System.
Two small probes will be deployed to intercept the comet when it's found. The mission is not about politics or religion. There are clues to the origin of the Solar System in LPCs. As the comet moves through space, the probes will create a 3D model of the comet and its surroundings.
There will be more comet-exploring missions in the future. We will continue to learn about them and which ones might be used for panspermia. We will get closer to a panspermia strategy as time goes on. It is possible that circumstances will force us to use our hands.
The discovery of comets is said to have caused the idea of directed panspermia to become more serious. The idea that humans could sow the seeds of a transformation that would last millions of years was considered absurd until recently. The discovery of comets outside of the solar system has changed everything.
The authors describe their vision of a biological universe. The goal of Panspermia is to increase the richness and diversity of life in the universe. Future generations will be able to do it even though we don't have the technology. Although we currently lack the technology to harness these comets as biological delivery vehicles, there is no difficulty in understanding what is needed to do so and in refining the strategy to achieve the goal of seeding the galaxy with life.
There is a haunting aspect to panspermia as well. There is no world that remains hospitable forever. We have a duty to spread life wherever we can because every instance of life faces extinction.
Are there any differences between directed and natural panspermia? It might be the right thing to do when we know it is the right thing to do. The Great Filter might force us to take a bold step. In order to find hospitable cradles throughout the universe, humanity might be spreading life elsewhere. Life can continue even after the cycle has ended.
Panspermia is a tip of the hat to life before we die. The setting of a science fiction film would be a dying, resource-depleted Earth with its biosphere in tatters and its aging Sun bathing it all in an eerie light. The last few hundred thousand bedraggled humans would gather the resources they needed to build one last craft. One last time, they would watch the flare of a rocket, loaded with inoculant, and headed for a rendezvous with a comet that was passing through our inner Solar System.
Is there anything more dramatic than birth and death on a planet?
Do not allow yourself to be lulled into a good night.
The light is dying.
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