Everything Everywhere Daily: History, Science, Geography & More - Could There Be Extraterrestrial Life In Our Solar System?

Starting point is 00:00:00 One of the biggest questions that humanity has asked is, are we alone in the universe? The possibility that there are other civilizations we could one day communicate with has tantalized people for years. However, before we can answer that question, there are other simpler questions we need to answer, such as, is life even possible outside of Earth? The place where we might be able to answer that question is in our own backyard. Learn more about if there's extraterrestrial life in our solar system on this episode of Everything Everywhere Daily. What if your perceptions about the past were wrong? ThruLine is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed.

Starting point is 00:00:53 It effectively turned day into night. And how it shaped the world now. Time travel with us every week on the ThruLine podcast from NPR. Before I go any further, let me say that this episode is not about alien intelligence, alien civilizations, UFOs, or alien encounters. Those might be worthy of discussion at some point in the future, but this episode is focused on something much simpler. This episode is focused on the search for alien life. Not necessarily intelligent or complex life, just very simple life, not even multicellular life like plants or animals, just simple life on a par with single-celled organisms.

Starting point is 00:01:37 The discovery of any sort of life that exists outside of Earth would be a groundbreaking discovery and one of the most important in the history of humanity. The search for alien life, and single-celled organisms would indeed be alien life, is part of the nascent scientific field called astrobiology. Astrobiology is a multi-disciplinary field of scientific inquiry that focuses on the study of life in the universe. It combines principles and methods from various scientific fields, including biology, chemistry, physics, astronomy, and geology, to explore the origins, evolution, and future of life, both on Earth and beyond.

Starting point is 00:02:15 The main goal of astrobiology is to understand the conditions and processes that give rise to life and determine if life exists elsewhere in the universe. At this point, astrobiology is primarily a theoretical discipline, because we haven't found life anywhere else. We're limited by our current technology on where we can even search. If we should find exoplanets that would be suitable for life around other stars, there's no way we could possibly reach them. That means, like it or not, our search for life has to take place in our own backyard,

Starting point is 00:02:48 our solar system. So what exactly are we looking for? We aren't necessarily looking for life as it would exist on Earth. Life on Earth is based on DNA, and save for viruses, is cellular. That could be what exists outside of Earth, but we don't know that. We're looking for something that meets the basic definitions of life. The definition of life, and there is no universal agreement on this, includes some of the following attributes. Organization. Something living would need to be organized and show some sort of complexity to differentiate it from non-living things.

Starting point is 00:03:26 Metabolism. This would involve chemical reactions which would allow the life form to acquire and utilize energy. Growth and development. This would imply the ability to grow and change over time as it moves into different phases of its life cycle. And finally, reproduction, the ability to create offspring with similar characteristics to itself. There's a great deal of debate as to what other criteria define life, but for the most part, I think most biologists would agree on these features as being a minimum. So where exactly do we start looking to try and find life when we don't even know exactly what we're looking for? Well, if a life form is to show metabolism, it means the transportation of energy. In a solid, nothing would really move.

Starting point is 00:04:10 So if atoms and molecules are to move to support metabolism in the form of chemical energy, that would imply some sort of fluid. There is one fluid that we know works for sure, and it also happens to be rather abundant in our solar system. And that is water. Water has been called the universal solvent. It plays a part in every cellular form of life on Earth. Moreover, there is evidence of water, at least in the form of ice,

Starting point is 00:04:37 all over the solar system. So the search for liquid water would be a pretty good place to start. The next question is, where can we find liquid water in the solar system outside of Earth? Liquid water can only exist within a certain range of pressure and temperature. The first place to look, and the place we have been looking, sort of, is on Mars. Mars is much colder than Earth. It has a much thinner atmosphere and it can't trap heat very well. That means that liquid water can't easily exist on the surface like it can on Earth.

Starting point is 00:05:08 But we know that there is water on Mars. Both the north and south poles of Mars have ice caps, which consist mostly of water ice but also some CO2 ice, aka dry ice. Moreover, ample satellite observations of the Martian surface, as well as surface rovers, have found evidence that at least at some point in the past, liquid water was flowing on the surface of Mars.

Starting point is 00:05:31 There are dry riverbeds and erosional features. The big question is if liquid water can still exist on the surface today. Right now, evidence seems to indicate that it can, at least temporarily. There have been observations of what are known as a reoccurring slope linee. These are erosional features on slopes that change every season. In particular, they tend to change when the temperatures are warmest on Mars. These erosional features look just like what you would find on Earth. While temperatures on Mars are overall much colder than Earth, near the equator, it is possible for temperatures to to reach as high as 21 degrees Celsius or 71 degrees Fahrenheit during the middle of the day.

Starting point is 00:06:14 This might allow for a liquid brine to seep out of the soil and to flow for short periods of time. The brine part is important because salty water has a lower freezing point than regular water, which is why you use salt to melt ice in the winter. If liquid water was more abundant in the past, and that seems to be the case, it might have been possible for some form of microbial life to have arisen on Mars. Some descendants of those ancient microbes might still be able to eke out in existence in these places where water can briefly melt. We know that there are extremophiles on Earth that can exist under such conditions, so it isn't out of the question. Any sort of life that could possibly exist there would probably have an extremely slow metabolism,

Starting point is 00:06:56 similar to the microbes that live deep underneath the surface of the Earth. They have lifespans that can reach into the centuries. Despite all the probes, landers, and rovers that have been sent to Mars, only two have actually carried instruments to check for signs of life directly, the Viking landers. They ran several tests on Martian soil, and some of the results were inconclusive. And I've previously done an entire episode on this topic if you wish to revisit it in more depth. There have been other positive signs which could indicate life on Mars as well.

Starting point is 00:07:27 This includes the presence of methane in the atmosphere and the discovery of organic chemicals in the soil. Future planned Mars missions will search more directly for life. The ExoMars mission by the European Space Agency will carry the Rosalind Franklin rover, which will contain a laboratory for searching for biosignatures, as well as a drill that can take samples from two meters deep. The mission that researchers are really waiting for is the Mars sample return mission. This would literally bring samples of soil back to the Earth where they can be studied more extensively. While Mars is a good candidate for finding life,

Starting point is 00:08:01 it's not the only one. Another target that is tantalized researchers is Jupiter's moon, Europa. Europa is basically a giant ball of ice. On the surface, it would be too cold for anything to survive. However, beneath the surface, it's believed that there could be an entire ocean of water. The tidal forces created from its orbit around Jupiter provide enough internal friction to melt the water underneath the surface. Moreover, the tidal forces could create thermal vents,

Starting point is 00:08:31 which would serve as a transportation vehicle for nutrients into the water. Surface features seem to indicate the presence of water underneath the icy crust. Cracks and ridges on the surface seem to indicate liquid water, filling the cracks when they open up, and freezing. Europa arguably has a far greater potential for life than Mars does because of the enormous reservoir of liquid water. The problem is that Europa is much further away than Mars and is much more difficult to reach.

Starting point is 00:08:58 And if there is life, it would be buried under the water. are 15 to 25 kilometers or 10 to 15 miles of ice. Almost everything we know about Europa has come from fly-by missions to Jupiter. There are future missions to Europa that are planned, but as of right now, they too are all fly-by missions. There is a Europa lander mission that's been discussed, but as of today, nothing has been approved and nothing has been confirmed. While Europa has one of the best potentials for life in the solar system, it's not the only

Starting point is 00:09:29 ice moon in the solar system. Saturn's mood of Enceladus is an ice moon, and geysers of water vapor have been observed on its south pole, indicating a liquid sea below the surface. Moreover, the Cassini mission detected complex organic molecules in the ice plumes, which are necessary for life. And the problem again is that Saturn is even further away than Jupiter. It has all the problems of exploring Europa, but even further away. Two other moons of Jupiter, Ganymin and Callisto, are also potential places where life could exist. Ganymin is the largest moon in the solar system and the only one with its own magnetic field. It primarily consists of rock and water, and it also might have a subsurface ocean.

Starting point is 00:10:10 Clisto is very similar. It is composed of approximately equal amounts of rock and ice with plenty of organic compounds that have been identified, and it too may have a subsurface ocean. It's actually the third largest moon in the solar system and is larger than the planet Mercury. There is one other moon that some think could harbor life, but it's different from all the others. It is a moon that has an atmosphere almost as thick as Earth, and it's the only other body in the solar system that has liquid on the surface. It's even believed to have rain, rivers, and lakes. I'm talking about Saturn's moon, Titan. The catch is that the liquid on the surface isn't water.

Starting point is 00:10:47 It's hydrocarbons such as methane and ethane. The surface of Titan is cold enough for these hydrocarbons to exist in a liquid form, but it's far too cold for liquid water. The hydrocarbons show that there's plenty of the basic molecular building blocks for life available, and here I'll refer you to my previous episode on the Miller-Yuri experiment. What is totally unknown is if life could exist without water. Is it possible to use some other liquid like methane or ethane? If life did evolve on Titan, it would be radically different than that which arose on Earth, or even potentially life found on Mars or the icy moons of the solar system.

Starting point is 00:11:23 These interplanetary bodies that I've listed are the best and most obvious places to look for life in the solar system, but they're certainly not the only places where some sort of simple life could possibly exist. One possible location would be in the atmosphere of Venus. The pressure on the surface of Venus is 95 times greater than that of Earth, and the average surface temperature is 900 degrees Fahrenheit or 480 degrees Celsius. However higher in the atmosphere, conditions are quite different. temperatures are moderate, and there exists a zone where life could potentially live. The big question is whether life could exist without a solid surface or a liquid medium,

Starting point is 00:12:03 and could life use a gas as a fluid? As of right now, there are far more questions than answers when it comes to life outside of Earth. So far, we haven't found anything. But in the big scheme of things, we also haven't looked very hard. We've landed a few robots on Mars, and we've taken some distant images of moons, but that's about it. The process of searching for life may take decades or even centuries, but at least now we have an idea of where to look. If we can find signs of life, any life, no matter how simple, elsewhere in our solar system,

Starting point is 00:12:38 it will perhaps be the greatest scientific discovery in history. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Thor Thompson and Peter Bennett. Today's review comes from listener Sophia over on Apple Podcasts in the United States. She writes, very interesting and informational. I love this podcast. I listen to it a lot, and I'm not in the completionist club because I'm on the younger side and do not like scary stuff. But I am very grateful that you make this podcast because it makes boring days a lot more interesting. Thank you so much.

Starting point is 00:13:12 Well, thank you, Sophia. I'm really glad to know that you're enjoying the show. I hope the show keeps you entertained and that you remain a listener for years to come. Remember, if you leave a review or send me a boostogram, you two can have it read on the show.

Everything Everywhere Daily: History, Science, Geography & More - Could There Be Extraterrestrial Life In Our Solar System?

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