I first saw a picture of a tardigrade when I was a child, and even then, I was fascinated. I prefer the more affectionate term “water bear”, and these cute little “micro-animals” are a classic example of just how resilient life can be. As we briefly discussed in class, tardigrades have survived exposure to outer space and can also survive other extreme temperature and pressure conditions.
Tardigrades are perhaps the closest thing we have on Earth to an extremophile, a term we use to describe organisms that can live in extreme environments. As we learned in class, there are many worlds in our solar system that could potentially support life, such as Europa and Enceladus, but conditions are still quite severe there. If life does exist on them, they are likely going to be similar to tardigrades.
Tardigrades and other species are important because they can serve as “pioneer species”, potentially to help colonize other worlds with life. Every ecosystem has layers of species, and primary simpler species must exist for more intermediate lifeforms to feed on. Through the process of ecological succession, more advanced forms of life can develop if simple lifeforms exist. There is currently some evidence and speculations that tardigrades could survive on Mars, and could theoretically be a nexus for future development of extraterrestrial life.
a. I was most surprised by how much we can discover about celestial bodies from our long distances. In the cases of other stellar systems, we may not know so much, but within our own, we’re able to study other bodies and make deductions about their properties to such a granular level– and this was shocking to me! Examples include our “knowledge” (more like “very strong theories”) about Europa’s properties, our understanding of magnetosphere’s and what it allows us to understand about planetary system development, and especially what we can learn about the potential for life! These blog posts allowed me to explore topics that were, at times, a little tangent to the class, but nonetheless relevant to astronomy, including the artist representations that we have of what Europa’s subsurface oceans may look like (Image 1).
(Image 1 from New Scientist, displays theorized layers beneath Europa’s surface with distinct geysers generated by tidal forced, also depicting Jupiter in the background)
b. Before taking this course, the topic I was most interested in learning more about was exoplanets. While this is obviously not about our solar system itself (since exoplanets are the planets outside of our system), I was fascinated to think about how we use the knowledge of our own solar system. Since we can analyze the planets in our own “backyard” much better than those that are multiple light-years away, I was curious to how we generalize the knowledge of that which we can study best to the rest of the galaxy/Universe.
c. This class made me most value how astronomy connects many different fields within STEM (physics, chemistry, and geology), all which work in tandem to allow us to be (or, at least, feel) so well informed. In order to understand, for example, what happens after surface impacts or consistent bombardments, there must be a connection of understanding the gravity and more physics-related properties and the materials and densities associated with geology (and physics, too, of course).
d. After taking this class, I hope to continue learning more about the development of new projects within the field of astronomy. As mentioned in class, JWST makes constant groundbreaking discoveries and, alongside existing and upcoming missions, I aim to continue keeping up with the news and looking through these new discoveries with the lens of our Solar System class. As an astronomy minor here at Vanderbilt, I want to continue having astronomy be a topic of interest (or maybe even a “hobby”) of mine. The moments where I feel “mind-blown” or “taken-aback” by either the vastness of space or the profundity of our knowledge of it, I feel like space exploration is like the “Christopher Columbus-type of exploration” of our times.
(Image 2 from Creative Fabrica, an art piece depicting Christopher Columbus and his colonizers as space-farers)
e. The class has definitely given me a new perspective on what astronomers do. As opposed to just looking through telescopes and “hoping to find/catch something”, astronomers analyze data and run tremendously complex simulations in order to solidify (or sometimes revolutionize) our understanding of the Universe and our place within it. With the introductory astronomy courses here having labs associated to them where students having observation events with telescopes, the idea of looking through telescopes as the main occupation of an astronomer could be understandably flawed (:
The Fermi Paradox describes the contradiction between high and low probability of extraterrestrial civilizations that exist in the universe and the lack of evidence for, or contact with, such civilizations. The term is named after the physicist Enrico Fermi who asked “Where is everybody?” during a conversation about the likelihood of alien life in the 50s.
Since there are sooooooooo many stars in our galaxy, many are very likely to have habitable zones similar to that of Earth. Because of this the probability of intelligent civilizations emerging SEEMS high. With the estimated age of our galaxy being over 13 billion years, some of these civilizations should have plenty of time to develop into very advanced species. However, we have been searching for decades and no definitive evidence of alien life has been found. (But really do we trust our government to be truthful about this completely? Recently in the news there has been a whole lot of things admitted from former government employees).
There are a few theories as to why we supposedly haven’t run into them yet; one is that intelligent civilizations are just extremely rare and short lived separate like blips across billions of years. Another is that advanced civilizations are deliberately avoiding us for various reasons. Another may just be that our technology is not advanced enough to find ones that may exist yet.
The Drake Equation is a formula proposed to estimate the number of technologically advanced civilizations within a given galaxy that may be capable of communicating with us. It doesn’t calculate anything with certainty but, instead, aims to stipulate that if we give X, Y, Z, criteria, what would we expect to see? How many civilizations would we expect to exist given these criteria? If the answer is anything more than 1 (us), how come we don’t see any other technologically advanced civilizations? What are the odds? Obviously, these calculations are highly speculative, as many of the variables are undefinable. Instead, all we can do is create estimates and guesses, using Drake’s equation in order to comprehend the bounds of our expectations.
The equation is defined below (Image 1):
(Image 1 from Phys.org, diagram on Frank Drake’s equation explaining all variables)
In the Milky Way, the following 3 are the estimates for each of the variables we somewhat know:
R∗ = around 1-3 stars per year fp = most stars have planets, fraction is close to 1 ne = estimated 0.2-1 per system
The next variables become extremely speculative, since we don’t have any relevant datapoints to draw numbers/statistics from:
fl = highly uncertain, since our only sample is ourselves– Earth. Some believe life arises frequently under the right conditions, but others argue it may be more rare. fi = depends on how often simple life evolves into intelligent life. On Earth, this took billions of years, so this fraction could be very small fc = even if intelligent life does occur on another planet, this variable is made to account for the fact that they must develop technology (such as radio signals) in order to be detectable. L = how long a civilization has the ability (and desire) to communicate. If all civilizations were short-lived, they would make communication less likely.
This is where it gets even more fascinating: given that there are 100,000,000,000+ galaxies, each with an average 100,000,000,000 stars. Each of these stars has an estimated average of at least one planet per star (Space.com) (Astronomy Magazine) (NASA). If we combine these numbers, we get the following total number of expected/estimated planets in the Universe:
(# of Galaxies) x (# of Stars p/ Galaxy) x (# of Planets p/ Star) = total # of planets (100,000,000,000) x (100,000,000,000) x (1) = 10,000,000,000,000,000,000,000 = 1 * 1022 planets
This estimate (which is very, very rough) equates to about 10 septillion stars. While plugging in actual values for all the variables in Drake’s Equation is a long process to explain, you can easily imagine the impact of a number as large as 10 septillion on the equation. Regardless of exactly what you input as each variable, the number you get will likely be shocking. In reality, any number above “1” would be mind-blowing; if your equation was to be right and your value for N was >1, you’d be identifying the necessity for life to exist elsewhere– statistically.
The image below was helpful for me to visualize this idea. Each dot in the image below represents a “candidate world” to have civilization. Each of the colored “sheets” represent a “requirement” the world must meet in order to still be a candidate to have civilization. As the diagram progresses through each sheet, the candidates-list becomes smaller and smaller (Image 2).
(Image 2 from AstronomyNotes.com, displaying a diagram representing Drake’s Equation)
Extremophiles are organisms capable of living under extreme conditions. This includes but is not limited to extreme temperature, radiation, pressure, and pH level. Given the extremely resilient nature of these organisms, they are some of the most abundant life forms. These creatures are fascinating as they have helped to stretch our knowledge on the limits of life, informing investigations on possible extraterrestrial life.
There are several classes of these organisms based on the severe environmental condition they are capable of enduring. However, these categories are not exclusive as certain Extremophiles can belong to multiple categories. These Extremophiles are referred to as Polyextremophiles. Below are examples of other Extremophiles:
Acidophile: Optimal growth at pH levels of 3.0 or below
Alkaliphile: Optimal growth at pH levels of 9.0 or above
Capnophile: Optimal growth in high concentrations of Carbon Dioxide
Halophile: Optimal growth at a concentration of of dissolved salts of 50 g/L or above
Oligotroph: Optimal growth in nutritionally deficient environments
Cryophile: Optimal growth at temperatures of 15 degrees Celsius or lower
Thermophile: Optimal growth at temperatures of 45 degrees Celsius or higher
The study of Extremophiles, as mentioned before, is useful in the field of Astrobiology as their existence helps to map out the limits of life on Earth in extraterrestrial environments. For instance, the deserts of Antarctica contain numerous severe environmental conditions such as harmful UV radiation, extremely low temperatures, high salt concentration, and low salt concentration. Coincidentally, these conditions are very similar to Mars. This means that finding microbes who may survive these conditions provide viable evidence that there may be extraterrestrial Extremophiles on Mars.
I was very surprised that there are so many bodies in our own solar system that have a real chance of having some sort of microbial life. I always thought the other planets and moons in the solar system were much too far away from the sun or too close to have life. It surprised me that with internal heating, a planet or moon could get the conditions for having life far away from the sun, like Europa. It seems like a sure shot that there must be some sort of bacteria in the ocean on that moon because the conditions almost mirror some extreme areas on Earth like the north and south poles.
At the beginning of the semester I wanted to learn more about the sun and the northern lights because they were much more active back home all of a sudden and I really didn’t understand why. Now I understand about solar wind and Earth’s magnetic field and how it protects us but also is what creates the great light shows. The sun is a very active, explosive thing and sends different levels of solar wind at different times which is why there are not northern lights every night.
I really appreciate astronomers and what it took for them to learn all this about the solar system. It blows my mind that just from sitting here on Earth (except the probes) we could deduce what Jupiter is made of, that there is water underneath of Europa, and even what an exoplanet’s atmosphere is made up of lightyears away. I have a great respect for their ingenuity in figuring all this stuff out.
After taking this class I am very interested in learning more about life outside of Earth. It seems like if we are finding places with good chances of life in our own solar system, then there must definitely be a planet out there that has life just like we do. I have a big appreciation for just how massive the Universe is now too, so it just seems like the chances are in our favor for there being life out there somewhere since there are just so many stars and planets. Even if it was purely chance that this all started here on Earth, and the chance is extremely miniscule that life would start, the sheer volume of planets means there is a pretty good chance it would accidentally happen again.
Before I took this class I didn’t think that being an astronomer was as impressive of a science as others. I imagined they just observed the sky. In reality these are some of the smartest scientists out there. They are making scientific discoveries and laws on objects millions of miles away, some that they can’t even see. There is a lot more math, physics, chemistry, and even biology in some cases than I expected.
As generations of humans have looked out on the stars, a never ending barrage of questions has ensued. As we learned that these celestial bodies were stars and planets similar to our own, the natural next question was is there anybody else like us out there?
The bad answer is no. The hopeful answer could be we just haven’t found them yet. Through new technology we have found many exoplanets around stars in the Universe. Some may have the conditions to harbor life as we know it. So what are these conditions needed for life? There are three main things: liquid water, organic elements (such as carbon and oxygen), and an energy source. These three things exist on many planets we have discovered, and many objects in our own solar system. The reason that we have not found anything yet is due to the fact that the technology is not there yet to search for life on these distant planets. The only way would be for an intelligent life source to send us a signal (and we are searching for those signals). Radio telescopes are used to detect low energy radio waves that come to Earth in an attempt to find an alien signal.
Although it would be very cool to find intelligent alien life, the most probable would be microbial alien life. There are many different schools of thought on how life started on Earth. The two main ideas are that life originated completely from Earth, and that during the heavy-late bombardment life came from an alien planet and settled on Earth. This life would have been an extremophile, capable of living through the vacuum of space and reviving once on Earth. Experiments have actually been done on extremophiles in the International Space Station and they discovered that these extremophiles would go dormant in space and revive once brought back into an atmospheric, livable environment.
So where would these microorganisms be living in space? There are many exoplanets as stated before, but the technology for detecting extremophiles on planets that far does not exist yet. The best chance is in our own solar system with probes such as the Europa Clipper that are going out to search for life on objects in the solar system. We won’t have a definite answer for many more years about life on Europa, but until then we will keep scouring the sky for signs of it.
As one may have gathered from reading the many, many pages of “The Cosmic Perspective,” the human race has learned a lot about the universe. We can determine the masses, chemical compositions, and orbital paths of celestial bodies. We’ve identified thousands of planetary systems in outside our own. We know how stars are born and die, and we have strong theories about how all that we see came to be. It would be naive to assume we are the only civilization aware of our place in the universe. Yet, as we peer into the cosmos from our floating rock, we find ourselves remarkably alone. As physicist Enrico Fermi puts it, “So where is everybody?”
An image of the Sagittarius C region of the Milky Way, here for aesthetic reasons
The assumption that we are not unique has been a powerful tool for astronomers. It enabled us to recognize the Sun as the center of our solar system and prompted us to search for evidence of exoplanets throughout the Milky Way. Assuming there isn’t anything particularly special about Earth, it might seem strange then that we haven’t found even microbial life on any of the other objects in our solar system. If we consider the wide variety of life forms we currently know of, there seems to be three basic requirements for life: a source of nutrients, energy to fuel life activities, and liquid water.
Nutrients and energy are practically omnipresent: even meteorites and comets have life-building molecules, and almost every world has sunlight or internal heating. Thus, the pursuit of liquid water has driven our search for life. Mars has evidence of harboring liquid water in its past, and astronomers are hopeful that pockets of water and water ice still exist underneath the surface, but no definitive evidence of life has been found. Europa is believed to have a massive subsurface ocean, but with limited energy sources, any life found would likely be microbial. Titan has a substantial atmosphere and may have an ammonia/water mixture that could support life, but we still haven’t detected anything. On Earth, we know of extremophiles that can survive in basically any climate imaginable: extreme heat, cold, acidity, pressure, etc. The tardigrade can even survive in the vacuum of space. It seems like life should be abundant, and yet we appear to be alone.
Looking past our solar system, we probably can’t expect to identify any subsurface life like the kind we hope to find on Mars or Europa, as it would be hidden deep underground far away. Let’s narrow our target to intelligent lifeforms, ones capable of organizing civilizations and honing technology, like us. As our capabilities for direct observation are too rudimentary at the moment, our best bet at detecting these life forms is likely through interstellar communication: perhaps radio transmitters, high powered lasers, or some currently unknown technology. While we speculate about whether intelligent life will ever be found, it may be difficult to reason about what our chances of success are.
Enter the Drake Equation:
Number of civilizations = NHP x flife x fciv x fnow
This equation, authored by astronomer Frank Drake, combines several factors to determine how many intelligent civilizations capable of interstellar communication currently exist in the Milky Way.
NHP = Number of habitable planets in the galaxy.
flife = The fraction of habitable planets that have life.
fciv = The fraction of life-bearing planets that at some point have carried intelligent life capable of interstellar communication.
fnow = The fraction of civilization-bearing planets that hold these civilizations now.
While we can make extrapolations about how many planets are potentially habitable, the values of all the fractions remain mysteries. Perhaps life is only present on Earth, or perhaps there are troves of lifeforms just outside our view. There might be galactic civilizations that have colonized multiple planets, or there might be a single asteroid full of germs on the other end of the Milky Way. Maybe our cosmic neighbors died out before the Earth formed, or maybe future societies will read about us in their textbooks. Despite our best efforts, there is still so much we don’t and may never know about our universe. How terribly exciting it is to be here, if only for a moment.
Source: the Cosmic Perspective by Bennet, Donahue, Schneider & Voit
Thank you all for reading my blog posts. Please enjoy my final farewell and concluding thoughts on the course with information from the Pearson Textbook. Enjoy this Milky Way photo from the Farmer’s Almanac.
During the time throughout this course, the fact that surprised me the most was the geological activity of other planets and moons. I am not quite sure why, but I was under the false impression that the Earth was the only body that experienced many of these processes outside of volcanism. Additionally, I had no idea that the moons of other planets were so diverse and active. I believe this surprised me because people like to believe Earth is special. However, in the big picture, not much proves to be different.
Before the class, I wanted to learn about the outskirts of our solar system- from the final few planets outward. I learned that after the planets there is the Kuiper Belt and even a Theorized Oort Cloud. Not only did we cover what exists out there, but how it was formed and what it consists of as well! These were created by the gravity of the Jovian planets, such as Jupiter and Neptune and contain comets, asteroids, and dwarf planets.
After this class, I would like to learn more about other star systems. We briefly covered exoplanets and other star formation, but I would like to visit this more in depth. I would like to understand the creation of other star systems and if there are more like ours. However, part of this research is hindered by our inability to know such information due to current technologies.
Taking the Solar System class has increased my appreciation of astronomy. The hard work and dedication that goes into this subject allows us to learn more about the creation of our planet and species. By learning these facts, astronomers can shed light on other planets and star systems which may contain oddities or other forms of life such as extremophiles! The topic is ever-changing and ever-developing for the better of our own planet.
This class did change by opinion on what an astronomer does. To begin, I did not think about this much before class. I figured they would be analyzing boring data on the same planets and waiting on information to be sent back from probes sent to space. It is so much more than that. Astronomers are dealing with a constantly changing view of the world and clicking together puzzle pieces I would have thought to be impossible to put together from the outside. They look at data of far away places and new objects and bodies never looked at before!
Methanogens are a type of extremophile. While browsing information on extremophiles, these caught my attention because they “ convert inorganic organic compounds into methane and carbon dioxide” (ScienceDirect). These microorganisms prove to be responsible for human flatulence. In addition to their unique productions, Methanogens can be found in the guts of animals, deep marine sediment, and wetlands. These interesting creatures remineralize organic carbon and play a role in anaerobic environments. The extremophile methanogens can live in crucial environments like hot springs, submarine hydrothermal vents, kilometers underground and hot, dry deserts.
Information for this blog post was found here. The photograph was taken from Study.com.
