Earliest Evidence of Life: 3.49 Billion Year-Old Microbial Mats

 

Weighing The Other Evidence

Roughly a billion years after planet Earth's formation, complex microbial communities were already thriving along the windswept seashore, clinging to sediments and harnessing energy from sunlight instead of relying solely on chemical energy from rocks.

Although even earlier, more primitive bacteria known as chemolithotrophs—organisms that obtain energy by consuming minerals—likely evolved before these microbial mats, no direct evidence of Earth’s earliest life forms has been discovered yet. This is most likely because these simpler formed structures—such as simple biofilms or mats—are far less likely to be preserved in the geological record compared to the more complex and robust microbial mats that are the main feature of this article. 

Although studies have pointed towards 4.1-billion-year-old carbon signatures in zircon crystals from Western Australia’s Jack Hills, 3.77-billion-year-old hydrothermal vent structures in Quebec, and 3.7-billion-year-old Greenland stromatolites (Isua Greenstone Belt), they are contested for a variety of reasons. The 3.5-billion-year-old Australian fossils (the main topic of this article) display distinct cellular structures and chemical signatures and continue to represent the strongest and most widely accepted evidence for the earliest life on Earth.

Microbial Mats In The Pilbara region of Western Australia

Let's delve deeper into these fossilized remains of these early microbial mat communities, which, due to their photosynthetic nature, were crucial in gradually oxygenating Earth’s atmosphere, fundamentally altering the planet’s surface environment and paving the way for new evolutionary pathways.

Scientists initially noticed web-like patterns and textures in the Pilbara sandstones, which they later identified as microbially induced sedimentary structures (MISS). These features were determined to have formed through the interaction of microbial mats with sediment, resembling processes observed in present-day environments.

Scientists did not initially set out specifically looking for microbially induced sedimentary structures (MISS) in the Pilbara sandstones; rather, they discovered them while studying the region’s ancient rocks for signs of early life. Prior to this discovery, researchers had already found stromatolites and microfossils in the Pilbara, but MISS of such great age had not been observed before.

The team included Dr. David Wacey from the University of Western Australia, along with US colleagues Nora Noffke and Daniel Christian of Old Dominion University, and Bob Hazen of the Carnegie Institution for Science in Washington. Professor Wacey was affiliated with the ARC Centre of Excellence for Core to Crust Fluid Systems, the Centre for Microscopy, Characterisation and Analysis, and the Centre for Exploration Targeting.

Comparisons of these ancient MISS with those found in younger rocks and modern environments (noting close similarities in form and preservation style) supported the interpretation that the structures were biogenic - produced by living organisms.

Deep Dive Into Their Carbon Chemistry & Dating Methods

Scientists measured the ratio of the stable isotopes carbon-13 (13C13C) to carbon-12 (12C12C) in the carbonaceous material embedded within the sedimentary rocks. In abiotic (non-living) carbon sources, the 13C/12C13C/12C ratio is typically close to the terrestrial standard, with 13C13C making up about 1% of the total carbon. However, biological processes—especially photosynthesis—preferentially incorporate the lighter 12C12C isotope, resulting in organic matter that is depleted in 13C13C relative to inorganic carbonates. The measured δ13Cδ13C values in the Pilbara samples were significantly negative, consistent with the isotopic signature of organic carbon produced by photosynthetic bacteria such as cyanobacteria.

The total organic carbon (TOC) content was also quantified, and the distribution of organic matter was mapped within the sedimentary matrix. The presence of organic carbon, especially when associated with sedimentary structures indicative of microbial mats, strengthens the case for a biogenic origin.

Despite the clear isotopic evidence, no preserved lipid biomarkers (such as hopanes or steranes), proteins, or microfossil cellular structures were found in these samples. This is not unexpected given the extreme age and geological history of the rocks, which would likely have destroyed or altered such fragile organic molecules.

There is no direct evidence that zircon crystals are present within the 3.49-billion-year-old sedimentary rocks that contain the microbial mats in the Pilbara region. Instead, the age of these rocks has been determined by dating zircon crystals found in nearby or interbedded volcanic ash layers or igneous intrusions. This is a common practice in Precambrian geology because sedimentary rocks themselves rarely contain minerals like zircon that can be directly dated. By analyzing the uranium-lead isotopic ratios in zircons from these associated volcanic rocks, scientists are able to establish maximum and minimum age limits for the surrounding sedimentary layers and the microbial structures they contain. Thus, the widely accepted age of 3.49 billion years for the Pilbara microbial mats is based on zircons from related volcanic material, not from the sedimentary rocks themselves.

References:

Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia

 

Nucleobases Found In Meteorites And Their Implications For Astrobiology

 

Nucleobases And The Origin Of Life

Meteorites are fragments of space rock that found their way to Earth. Around 70% of them originated from three young asteroid families (Karin, Koronis, and Massalia) formed by collisions in the main asteroid belt 5.8, 7.5, and about 40 million years ago. The rest of discovered meteorites have been found to come from the asteroid Vesta, Mars, the moon, and possibly even small pieces of Mercury and Venus. 

Although meteorites are already very interesting on their own, the biological material found on them only enhance the intrigue that surrounds them. Nucleobases are nitrogen-containing biological compounds that form the fundamental building blocks of the complex macromolecules known as nucleic acids, including DNA and RNA. 

 

Nucleobases are nitrogen-containing, carbon-based compounds that form the fundamental units of the genetic code. The five primary nucleobases are adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U). These bases are essential components of DNA and RNA, with A, C, G, and T found in DNA, while A, C, G, and U are present in RNA. Other than genetic information storage, nucleobases play roles in protein synthesis, cellular metabolism (various metabolic processes, including energy transfer (ATP) and cell signaling (cAMP and cGMP), and enzyme cofactors (enzymatic reactions, such as coenzyme A, FAD, and NAD+). 

While finding nucleobases doesn't quite translate to finding extraterrestrial life, they are biological material that can give us great insight into the formation of more complex biological structures and a firmer understanding of extraterrestrial life. 

 

To form nucleic acids, these nucleobases must combine with specific sugar molecules (either ribose or deoxyribose) and phosphate groups through two types of chemical bonds: N-glycosidic linkages and phosphodiester bonds. N-glycosidic linkages connect the nucleobases to the sugar molecules. These bonds form between the nitrogen atom of the nucleobase and the anomeric carbon of the sugar, creating a nucleoside. 

 

Phosphodiester bonds, on the other hand, link the sugar-phosphate components, forming the backbone of the nucleic acid chain. This combination process requires suitable environmental conditions, such as appropriate temperature and acidity, as well as energy sources. In living organisms, special proteins called enzymes, like DNA polymerase, help facilitate this process. 

 

An important feature of nucleobases is their ability to pair up in specific ways - adenine (A) always pairs with thymine (T) in DNA (or uracil (U) in RNA), and cytosine (C) always pairs with guanine (G). This base pairing is crucial for the structure and function of DNA and RNA. 

 

In modern living cells, specialized enzymes help build these nucleic acid chains. However, when life was first emerging on Earth, other chemical pathways might have existed to join these building blocks together, possibly through alternative mechanisms for forming N-glycosidic linkages and phosphodiester bonds. Some theories suggest that nucleobases and sugars could have emerged from common precursors, potentially simplifying the process of nucleoside formation.

Carbonaceous Meteorites That Have Been Discovered 

A carbonaceous meteorite is any meteorite rich in carbon compounds while a carbonaceous chondrite is a more specific term for a class of stony meteorites that contain carbon compounds and have a particular internal structure characterized by the presence of chondrules (small, rounded grains composed of silicate minerals). 

Several carbonaceous meteorites have been found to contain nucleobases. The most notable of these are the Murchison, Murray, and Tagish Lake meteorites.

These meteorites have provided valuable insights into the potential extraterrestrial origins of life's precursors. In a groundbreaking study published in 2022, researchers used advanced analytical techniques to detect a diverse suite of nucleobases in these meteorites. The study identified both purine and pyrimidine nucleobases, including the canonical base pairs adenine-uracil, guanine-cytosine, and adenine-thymine, as well as some non-canonical ones like isoguanine-isocytosine and xanthine-2,4-diaminopyrimidine. This discovery is significant because it marks the first time that all five nucleobases used in life today - adenine, guanine, cytosine, uracil, and thymine - have been detected in meteorite samples.

 

The Murchison meteorite (a CM2 type carbonaceous chondrite) in particular, has been a rich source of organic compounds. Prior to the 2022 study, it had already yielded seven purine bases and one pyrimidine base. The new research expanded this list, identifying various pyrimidine nucleobases such as cytosine, uracil, and thymine, along with their structural isomers like isocytosine, imidazole-4-carboxylic acid, and 6-methyluracil.

 

These findings suggest that a diverse range of nucleobases could have been available on the early Earth, delivered by meteorites. The similarity between the molecular distribution of pyrimidines in these meteorites and those found in photon-processed interstellar ice analogues indicates that some of these compounds may have been generated by photochemical reactions in the interstellar medium before being incorporated into asteroids during solar system formation.

The spontaneous formation of nucleobases on asteroids and potentially other solid bodies in space is a positive sign that at least these building blocks are not so rare as an early step toward more complex extraterrestrial organisms.

References:

 

Identifying the wide diversity of extraterrestrial purine and pyrimidine nucleobases in carbonaceous meteorites

Book Review: "Systems Approach To Astrobiology" By Benton C. Clark & Vera M. Kolb

 

    I have just finished reading this wonderful book on astrobiology. It's not a long read, but some of the language is a little technical and it requires at least some background and understanding of general biochemistry terminology. But overall, if you're looking for a clear introductory book for learning more about astrobiology, I would highly recommend Systems Approach To Astrobiology.

    The first chapter goes through general understanding of what astrobiology is, including what it aims to achieve and what type of scientific field it is. Chapter one also goes through what a system is, and its composition and characteristics. What this book does well is emphasizing the importance of systems analysis and analyzing data through the context of an entire system rather than in isolation. This is very crucial in astrobiology and systems chemistry, because so many subsets and subsystems depend on each other and are highly affected by each other.

    Chapter 4 goes into depth on analyzing the different definitions of a living system and when a system can count as living. This can of course become very unclear as there are many complex steps in the transition from abiotic chemistry to the first protocell. The chapter also goes into the uniqueness of living systems, subsystems of metabolism, ATP, alternative primordial energy currencies other than ATP, and more.     

    Chapters 5 & 6 are about systems chemistry and prebiotic chemistry.  Chapter 5 covers molecular networks, self-replicators, and emerging features as prebiotic evolutionary transitions. Chapter 6 discusses prebiotic chemical feasibility, molecules found in space from meteorites and other sources, differences between modern enzymes and prebiotic reactions, and also goes through some learning phases experienced by origin of life researchers throughout the years and where the field is now. Chapters 7-10 go through all of this through a systems standpoint, and weigh these prebiotic chemistry problems against other factors within a gigantic system with different feedback loops, intricate chemical complexity, etc.

    Chapter 11 is focused on panspermia and the interplanetary transport of life. Chapter 12 is a general overview of systems analysis. 

    I just finished the book today and recommend it to all of you interested in planetary science, astrobiology, origin of life, molecular evolution, etc. Enjoy! 

    

    

In An RNA World: Why RNA Or An RNA-Like Nucleic Acid Is Such A Popular Candidate For The Origin Of Life

 

A Divided Puzzle

The origin of life remains a puzzle, and may always be that way in the sense that we won't ever completely understand the exact chemistry that gave rise to the first protocell. But the main reason as to why this is the case is the fact that there are many plausible scenarios in which it could have occurred. Never mind the complex chemistry that gave rise to the first building blocks - there is still much division as to what these first building blocks even were. Besides the RNA world, we have metabolism-first, panspermia, iron-sulfur world, clay hypothesis, and more. However, the RNA world remains to be the most plausible explanation for abiogenesis for many scientists. 

The Uniqueness Of RNA 

There are certain features and capabilities of RNA that render it unique and favorable in terms of prebiotic chemistry. For one, it somewhat solves the chicken-and-the-egg paradox in the sense that it functions as a genetic molecule that also catalyzes its own replication. And this replication in turn serves as somewhat of a kickstarter to Darwinian evolution in a molecular genetic sense (opposed to purely chemical systems preceding its emergence). Selection based on the efficiency of RNA replication in which those that display improved replication are selected for seems plausible in and of itself. but another chicken-and-the-egg paradox arises. Some form of evolution is required for the first primitive self-replicating ribozyme to emerge, but without the self-replication feature, there can't be an evolutionary search.  One theory that's been suggested as to the origins of RNA evolution without the assistance of an evolved catalyst is template-directed synthesis, in which some copying occurs preceding the first replicase ribozyme. Basically, RNA can drive chemical reactions as well as store genetic information, making proteins and DNA unnecessary in this origin of life scenario. 

Pre-RNA

While RNA seems like a good candidate for the first self-replicating molecule, it's probably not the very first one. There are a few reasons for this:

(1) It's hard to form long RNA molecules without enzymes.

(2) The building blocks of RNA (ribonucleotides) are difficult to create naturally.

(3) Forming RNA requires a specific type of chemical bond (3' to 5' phosphodiester) to happen repeatedly, but many other reactions could interfere.

Because of these challenges, scientists think the first self-replicating molecules might have been simpler polymers that were similar to RNA. We don't have any traces of these molecules today, but their simpler structure makes them more likely candidates for the first information-storing and catalytic molecules on Earth.

The transition to an RNA world might have happened when these simpler molecules acted as templates and catalysts to create RNA. Lab experiments show that one such simpler molecule (PNA) can indeed act as a template for making RNA.

These pre-RNA molecules likely also helped form the building blocks of RNA from even simpler chemicals. Once RNA appeared, it could have gradually taken over the functions of the pre-RNA molecules, leading to the RNA world.

Emergence Of RNA On The Early Earth 

RNA emerged from nucleotides, likely in warm, shallow ponds on the early Earth. Organic (carbon-based) compounds would have leeched in through drainage and precipitation. Nucleotides likely formed from simpler precursor molecules in this mish mash of organic compounds, aided by wet-dry cycling as well as UV radiation as an energy source. 

The first cells with membranes likely formed when certain molecules that can interact with both water and fats (amphipathic molecules) spontaneously came together to create a barrier. This barrier enclosed a mixture of self-replicating RNA (or its precursor) and other molecules. We're not sure exactly when in the evolution of biological catalysts this happened.

Once RNA molecules were enclosed within these membranes, they could evolve more effectively as carriers of genetic information. This enclosure allowed for selection based on two factors:

(1) The structure of the RNA itself.

(2) How the RNA affected other molecules within the same enclosed space.

This meant that the sequence of nucleotides in the RNA could now influence the characteristics of what we'd consider a basic living cell. The membrane created a distinct unit, separating the internal environment from the external world, which is a fundamental feature of life as we know it.

References:

The Origins of the RNA World

The RNA World and the Origins of Life

Building Artificial Life: An Introductory Overview Of Synthetic Biology

 

What Is Synthetic Biology? 

While origin of life research generally pertains to figuring out the pathways of chemical systems that produced the earliest protocells (in a geochemically plausible scenario), there is a different yet overlapping field that is constantly approaching new frontiers - Synthetic Biology. Synthetic biology is directly concerned with building artificial life, whether it be in the form of protocells/cells, organisms with expanded or reduced genetic codes, synthetic DNA and genomes, hybrid biological systems, artificial organelles, and more. 

Synthetic biology relies upon multiple scientific fields in order to expand its horizons, including but not limited to - bioengineering, biotechnology, molecular biology, genetics, nanotechnology, systems biology, chemical biology, and more. Although synthetic biology has seemingly limitless potential world-changing capabilities, from gaming to medicine, I am most interested in it's ability to build artificial protocells in order to further understand the origin of life. That is what this blog post will focus on.

Synthetic biologists can be categorized into two main groups. One group uses unnatural molecules to mimic emergent behaviors from natural biology, aiming to create artificial life. The other group seeks to use interchangeable parts from natural biology to construct systems that function in novel ways. In both approaches, pursuing synthetic goals compels scientists to explore uncharted territories, addressing problems that are not easily encountered through traditional analysis. This exploration leads to the development of new paradigms that analysis alone cannot readily achieve.

Building Artificial Life

In 2010, leading genomic scientist Craig Venter and his research team essentially constructed a synthetic copy of a bacterium's DNA that, once transplanted into an organism, took control of its functions. Obviously, this is different than creating a complete living synthetic organism, but nevertheless, it was a massive leap for the field of synthetic biology. 

Cells are not only the building blocks of biological complexity; they are complex systems maintained by the coordinated interaction of multiple biochemical networks. Their replication, adaptation, and computational abilities arise from appropriate molecular feedback mechanisms. As recent decades have showcased the transition from the description-driven biology to the synthesis-driven biology, it has presented a common challenge to the fields of bioengineering and the origin of life - what are the proper conditions that lead to the emergence and persistence of living cellular structures? 

A hypothesis-driven approach to biology has enabled the control and design of new cellular functions and genetic circuits. Two main approaches have been considered towards protocell synthesis. The first one is a top-down approach and involves the construction of a minimal cell by reducing the genome of existing cells. The other main approach, bottom-up, involves starting from scratch: from scratch: a life-like entity is constructed via self-assembling molecular components, whether biological in nature or completely ad hoc chemical components. 

Although self-replication and evolution are important abilities of cells, they do not necessarily need to be end goals of protocells constructed via synthetic biology. The artificial cell (Acell) could replicate but not evolve, or even be completely unable to self-replicate. Either way, a simple self-sustaining Acell could persist under specific conditions, exchanging energy and matter with its surroundings without growing. Although this might seem like a limited scenario, it is quite intriguing: one could design or guide the self-assembly of a protocell capable of performing certain functions or computations in predefined ways.

This article is meant as a general overview of synthetic biology. I will delve deeper into the actual methods that scientists employ in protocell construction in future blog posts. 

References: 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9788358/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2442389/

https://ntrs.nasa.gov/api/citations/20020043286/downloads/20020043286.pdf

The Genomic Imprint of Evolution

 

Over a century ago, scientists relied on physical and anatomical evidence for the reconstruction of the evolutionary past, namely in the form of transitional fossils in geology/paleontology and vestigial structures in anatomy. It wasn't until the late 1960's and early 1970's that biologist Allan Wilson and colleagues utilized protein electrophoresis to analyze genetic variation among different populations, which led to a better understanding of human origins, including the "Out of Africa" hypothesis, which suggests that modern humans originated in Africa. This continues to be the consensus among scientists today.

Whole Genome Sequencing (WGS)

Whole Genome Sequencing (WGS) is a technique utilized in order to obtain complete DNA sequence of an organism's genome. In order for this to be done, all the genetic material of said organism must be analyzed, including both coding and non-coding regions. The first step of WGS involves collection some form of DNA from an organism, which could be blood, tissue, or other kind of sample. Genomic DNA is then isolated from the sample using DNA extraction methods. Following preparation, the DNA fragments undergo sequencing using high-throughput platforms such as Illumina, PacBio, or Oxford Nanopore. These platforms employ diverse sequencing technologies and methodologies, and generally involve decoding the sequence of nucleotides (A, T, C, and G) within each DNA fragment. Upon completion of sequencing, raw sequence data undergoes analysis through bioinformatics tools and algorithms. This process encompasses quality assessment, aligning sequence reads with a reference genome (if available), detecting genetic variations like single nucleotide polymorphisms (SNPs) and structural variants, and annotating genomic attributes.

Genome Sequencing: Evolutionary Relationships & Evolutionary Past 

Once a genome of a species is sequenced, it can be compared with the genome of another, which aids in the construction of phylogenetic trees which show how the two (or more) species are related to one another, including tracing evolutionary splits. The sequences can also uncover genetic changes throughout lineages, such as crucial mutations, gene duplications, and gene losses; all important processes that helped shape the current genome. Genomic data in addition to fossils found in a certain region can help reveal and pinpoint adaptations that assisted in an organisms survival in that specific period and environment. Instances of horizontal gene transfer, in which genetic material is exchanged between species, can also be detected. Analyzing the genetic diversity within a population of a species can illuminate the dynamics of its evolution, encompassing phenomena like genetic drift, natural selection, and gene flow. This knowledge plays a pivotal role in comprehending the evolutionary trajectories of populations across successive generations.

Genomic Fossils

Genomic fossils are remnants of ancient genetic material or sequences that have been preserved within the genomes of modern organisms. Transposable elements (TEs), also called jumping genes, represent a category of genomic fossils. These DNA sequences possess the ability to relocate or "jump" within a genome, occasionally integrating into fresh positions. As time elapses, certain TEs lose functionality, resulting in preserved "fossilized" duplicates within the genome. Investigation of these vestiges unveils the varieties of TEs that were operative in progenitor species, shedding light on their influence on genome organization and operation. Pseudogenes are gene duplicates that have accumulated mutations, causing them to lose their original functionality. These sequences act as genomic relics, mirroring the evolutionary journey of genes and gene families. Through cross-species comparison of pseudogenes, scientists can deduce instances of gene loss, duplication events, and alterations in function that have transpired throughout evolutionary processes. Occasionally, alleles or genetic variations that were previously beneficial can persist as "fossilized" remnants in the genome despite losing their selective advantage. These (known as ancient alleles) offer insights into past adaptations, selective pressures, and evolutionary shifts prompted by changes in the environment. Also, Certain non-coding DNA sequences, such as regulatory elements or sequences involved in genome organization, can be highly conserved across species. 

References:

Darwinian genomics and diversity in the tree of life

Worlds Beyond: The Search For Other Life In The Cosmos

 

Astrobiology, Geobiology, and Life Beyond 

The field of Astrobiology is concerned with finding biology on other planets or other solid bodies in space.  Geobiology is the study of the interactions between living organisms and their geological environment. It explores how life influences geological processes and how geological factors, such as minerals and rocks, shape and affect life forms. The two fields of course overlap in many ways, as emergence of life throughout the cosmos is greatly dependent on geochemical conditions.  Besides a solid surface with minerals, whether in the form of a rocky planet, dwarf planet, or meteorite, other predictors of life are gaseous atmospheres and water. Chemical reactions are the kick starter for chemistry to turn into biochemistry. These reactions could come about through meteor impacts, volcanic activity, solar rays, hydrothermal vents, and more (or a combination of things). We know that one or a combination of these things led to life emerging on our wet rocky planet of Earth, but how can we detect life on solid surfaces that are beyond our reach? Read on. 

The Pool Of Possibility 

What pool do we have to work with in terms of our options we have to work with? In an (observable) universe that may contain 100 billion to 200 billion galaxies, tens of billions to hundreds of billions of solar systems in each galaxy, and about 10^22 planets, the possibilities may seem endless, but when we go back to the requirements, we need to be more cautious and specific in what we're looking for.  For examples, many planets in the universe are (like Neptune and Saturn in our solar system) gaseous, and therefore highly unlikely to contain life. Other planets may be solid and rocky, but lack the other necessary components such as water and gaseous atmospheres. We can even get more detailed than that, and say that some wet rocky planets may have all the necessary ingredients except carbon, which is crucial for life on Earth because of its unique ability to form complex molecules through chemical bonding. Is non carbon-based life a possibility? Yes, but there's a lot of extraterrestrial chemistry that we know nothing about that would have to be studied in order to even begin to find out. The point is, the problem complexifies with the more (necessary) questions that we ask, and since astrobiology is a multidisciplinary field that incorporates astronomy, biology, chemistry, geology, physics, and more, we need to examine these problems through a systems-approach instead of a singular approach, meaning that we need to tackle each problem within the context of other factors instead of on its own. 

Life Detection Methods

In order to improve and expand our search for extraterrestrial life, we need to employ the most high-quality and cutting edge technology. Spectroscopy as a generalized technique in science is a scientific method of studying objects and materials based on color.  As applied to astrobiology, it's a technique that entails examining the light released or captured by a planet's atmosphere or surface. Researchers search for distinctive patterns, like indications of water, organic compounds, or gases such as oxygen and methane, which might indicate potential biological processes. Chromatography in astrobiology is achieved through simulation experiments and analyses conducted in laboratories using Earth-based analogs or synthetic environments designed to mimic extraterrestrial conditions.  Types of chromatography include gas, liquid, and ion. Gas chromatography is extensively used in astrobiology for analyzing volatile and semi-volatile organic compounds in samples related to extraterrestrial environments or analogs. Liquid chromatography is used in order to separate non-volatile and polar compounds, including biomolecules. Ion chromatography is employed to analyze ionic compounds, including inorganic ions and organic acids. Of course, direct imaging through telescopes is also employed,

but is subject to challenges because stars emit significantly brighter light than the faint reflections from planets. Methods such as coronagraphs, starshades, and interferometry are employed to obstruct or reduce starlight, thereby enhancing the detectability of exoplanets. Capturing images of distant exoplanets in our galaxy or neighboring galaxies necessitates the use of high-powered telescopes equipped with sophisticated adaptive optics technology in order to minimize atmospheric distortions.  Advanced telescopes like the Hubble Space Telescope (HST), the James Webb Space Telescope (JWST), and future space observatories are capable of high-resolution imaging. They can capture detailed images of planetary surfaces, including features like mountains, craters, valleys, and atmospheres.  Space probes and rovers have delivered detailed images of planets and moons within our solar system, revealing their geological characteristics and surface environments. Hopefully sooner than later, advancements in aerospace engineering and long distance space travel can put more rovers, probes, and astronauts deeper into space. We have already observed nucleobase formation in various meteorites, showing that spontaneous formation of genetic building blocks happens elsewhere.

Life Beyond Us: Conclusion 

Some scientists, like biochemist and molecular biologist Dr. Steven Benner think that microscopic microbial life is common on wet rocky planets. Dr. Benner has said that he thinks about 90% of wet rocky planets will have microbial life on them. Other scientists who work (in some way) in astrobiology are less optimistic in terms of the figures they cite. In terms of intelligent life, it largely depends on evolutionary biology and processes in evolution that would produce an intelligent organism. The fascinating endeavor of space exploration and life detection will be an evolving puzzle throughout the 21st century and beyond, and you can contribute to it by pursuing research in one of the many relevant scientific fields that make up astrobiology. 

References:

Astrobiology At NASA - Life Detection

Search for Life outside the Solar System