Clouds of sulfuric acid float through the crushing carbon dioxide atmosphere of Venus. Tens of thousands of volcanoes pockmark its surface. A runaway greenhouse gas effect turned the planet into a molten hunk of rock, but it wasn’t always like this. Earth’s “sister planet” may have once been covered in a shallow ocean. Had it not been for an alternative evolutionary path, Venus could have been teeming with life.
Still, the possibility that microbial life lives among the clouds of the Venusian atmosphere remains. No signs of alien life have ever been detected. Yet humanity continues searching, hoping for confirmation that we are not alone in the universe. The likelihood of finding extraterrestrial life, especially microbial life, increases as the field of astrobiology explores what makes a planetary body habitable. “How does life begin and evolve? Does life exist elsewhere in the Universe? What is the future of life on Earth and beyond?” According to NASA, these are the questions that astrobiology hopes to answer.
Astrobiology is defined as the origin, evolution, distribution and future of life in the universe. A young science, astrobiology looks at the history of life on Earth as well as the possible existence of extraterrestrial life. The two subjects are in fact interconnected. Life on Earth influences our search for life throughout the solar system and galaxy, which in turn shapes our understanding of life on Earth.
Life as We Know It
One of the main questions that astrobiologists are trying to answer is “What is life?” Life is often characterized by a spark, or essence. This explanation is ill-suited in scientific fields, however. Dating back to Aristotle, scientists and philosophers have struggled to define life, or to draw a boundary between living and non-living entities. The challenge comes from excluding things like fire or crystals, which grow using the same chemical reactions used by some organisms.
There are over 100 definitions for “life,” and NASA defines it as “a self-sustained chemical system capable of Darwinian evolution.” Landing on an agreed-upon definition of life may seem of little importance compared to finding it among the stars. However, in the process of exploring distant worlds, scientists have had to reexamine their criteria for discovering “life.”
July 20, 1976, Viking 1 became the first spacecraft to land on Mars. The lander was equipped with three biology package experiments, one of which came back with promising results. High levels of carbon dioxide in the Martian soil suggested the presence of microbes on the surface of the planet. However, the Viking gas chromatograph mass spectrometer (GCMS) failed to find organic molecules. Events like this have forced astrobiologists to consider the possibility that extraterrestrial life, if discovered, may not resemble life on Earth. Until we find an alternative to carbon-based life, we may never fully understand what it means to be alive.
Down to Earth
To better understand what life might be like on another planet, scientists must consider how life began on Earth. The origin of life, especially the evolution of intelligence, is a mystery that continues to puzzle astrobiologists. In one corner, scientists argue that if the clocks were rewound and animals since the Precambrian period were given a second chance to evolve, the chances of human intelligence emerging would be minuscule. Humanity’s rise depended on countless factors, not the least of which was an asteroid’s impact 65 million years ago.
Other scientists point to convergent evolution, a process in which unrelated organisms develop similar traits. Birds and insects evolved wings independent of each other. Through eyes the size of dinner plates, giant squids see the world not unlike land animals. Nature, it would seem, favors parallel paths that are destined to meet, even when an evolutionary line seems to depend on chance. However, technical intelligence has only evolved once on Earth — and maybe only once in the entire universe.
Are we alone in the cosmos? Is life on Earth the result of a complicated system where, if one element were to misalign, our planet would be as desolate as Venus? Or are habitable planets as abundant as stars in the sky? These questions have been debated for centuries, but as scientific knowledge grows, so too do our chances of answering them.
Humanity is inexplicably drawn to the stars, and its exploration of life in the universe continues. The Mars 2020 Perseverance Rover combs the Martian surface for signs of microbial life. Set to launch in a few short years, the Europa Clipper spacecraft will determine if Jupiter’s icy moon could harbor life. Finding life beyond Earth seems not only increasingly likely but inevitable thanks to achievements made in the field of astrobiology.
Explore the Origin of Life at UF
The University of Florida offers a Master of Science in Microbiology & Cell Science with a concentration in Medical Microbiology and a Graduate Certificate in Environmental Microbiology. Courses are entirely online and focus on microscopic organisms, including those that may have perpetuated life on Earth or that may be found in the cold reaches of space. As both a source of wonder for countless people through the ages and a significant area of scientific research, astrobiology is part of the UF microbiology curriculum as a dedicated course.
A Side Expedition Into Astrobiology
Available to all online graduate students, Astrobiology (MCB 5705) focuses on the origin, evolution and future of life in our solar system. Students in this course explore topics ranging from planetary habitation to planet and star formation to microbiology research aboard the International Space Station. MCB 5705 provides a firm foundation in astrobiology concepts and methodology, empowering students with the skills to analyze and summarize key literature in the field as well as prepare grant proposals on the subject.
Apply to one of our online microbiology programs if you’re interested in studying microorganisms known and unknown and their influence on humanity’s place in the universe.