With the increasing discoveries in space each year, more people are coming to believe that life may have originated from outer space. Alongside this belief, followers of the Panspermia hypothesis have been on the rise in recent years.
Carl Sagan, a renowned global astronomer, once stated that the nature of life on Earth and the possibility of extraterrestrial life are two sides of the same coin. Both of these issues could find their answers within the framework of the Panspermia hypothesis.
The Panspermia hypothesis suggests that life exists beyond Earth and that life as we know it on our planet has extraterrestrial origins. It posits that various celestial bodies, including other star systems, asteroids, comets, and even Mars, may have contributed to the formation of life on Earth.
What Is the Panspermia Theory?
Panspermia is an age-old concept dating back to ancient Greece. According to the Panspermia hypothesis, humans could be organisms that developed in other regions of the universe and whose genes infiltrated Earth via comets or meteorites impacting its surface. In modern times, notable astronomers like Chandra Wickramasinghe and Fred Hoyle have supported this hypothesis.
Although there is still no clear evidence to prove this concept, significant discoveries in the past century have made the Panspermia hypothesis more plausible. Some supporting evidence for the Panspermia hypothesis includes the existence of life in uncontrollable geological records that occurred approximately 3.8 billion years ago, close to the Late Heavy Bombardment (LHB) period. LHB was a time when the collision rate between planets in the solar system was much higher than today.
Many argue that any life on Earth before the LHB would have been wiped out, and today’s life might have originated from space through impacts on Earth. This is speculative, but when compared to the timing of life’s appearance on Earth, it carries weight in the argument.
Did Life Truly Come from Mars?
One particular meteorite discovered in 1984 in the Allan Hills region of Antarctica was initially cataloged as ALH8400 and garnered little attention at the time. However, in 1994, scientists conducted geochemical and microscale studies and discovered that this meteorite had originated from Mars, making it an exceptionally unique Martian meteorite.
ALH84001 was found to contain complex organic molecules called polycyclic aromatic hydrocarbons (PAHs), often associated with microbial activity. Additionally, it was found to contain iron sulfide combined with magnetite; typically, these two minerals do not coexist with carbonate minerals unless formed by biological processes.
Furthermore, scientists examined the meteorite and discovered peculiar nanostructures resembling certain bacterial species. These unique findings within the meteorite led many experts to believe they were evidence of the possibility of life on Mars.
These recent revelations about the ALH84001 meteorite forced some scientists to reevaluate it, sparking renewed interest. Over time, the data supporting the idea of life on Mars has been questioned by proponents of non-biological origins.
PAHs can form relatively easily in a non-biological environment when organic molecules are subjected to heat, and que-shaped entities resembling bacteria might be too small to have ever been living organisms.
However, magnetite and iron sulfide still stand as evidence for the presence of biology within ALH84001, as many of the magnetite particles have shapes and sizes resembling those of bacterial particles.
Currently, there is no known non-biological process for the formation of such magnetite particles combined with iron sulfide, making the question of whether life existed on Mars or not still unanswered. Even if it is established that life once existed on Mars, the possibility of life originating on Mars seeding life on Earth remains uncertain.
According to scientists, there are two major concerns regarding the prospect of life on Mars seeding life on Earth. First, is whether any form of life can survive the journey from Mars to Earth. Second, is there a basis to believe that life could potentially thrive on Mars more and earlier than on Earth in the past? Surprisingly, both questions may have affirmative answers.
Even if bacteria can survive the harsh conditions of space and a high level of hostility outside of Earth, can they endure the journey of millions of years from Mars to Earth? Interestingly, bacterial spores found in extinct bees preserved in ancient amber and saltwater mixtures trapped in ancient salt crystals suggest that bacterial spores can survive for up to 250 million years.
However, immersing in saltwater or amber within Earth’s environment is still milder compared to the conditions inside a wandering space rock.
Additionally, scientists argue that there’s reason to assume that life may have originally formed on Mars rather than Earth. While water is essential for life as we know it, its presence inhibits the production of life’s building blocks. Earth’s early history suggests it was nearly covered by a global ocean.
In contrast, Mars experienced periodic wet and dry phases throughout its early history. According to a current idea about the origin of life, life began in shallow water or puddles, exposed repeatedly to sunlight and drying cycles. This would lead to the stable accumulation of complex organic molecules over each drying cycle, eventually forming the basis of life.
Thus, it’s possible that life had a relatively easier time forming on early Mars than on Earth. There’s now a substantial body of scientific evidence supporting this as a highly credible theory.
The Possibility of Life from Comets or Asteroids
Another popular hypothesis among Panspermia proponents involves comets and asteroids. Chandra Wickramasinghe, an astronomer and mathematician, has argued that life could very well have originated from the inner portions of comets.
He continuously contends that the billions of cometary objects predicted to exist in the solar system have a much higher chance of supporting life than Earth’s early hostile environment.
Another suggestion is that a comet could have passed through the upper atmosphere of a life-rich planet, allowing life to hitch a ride on the comet.
If comets delivered life to Earth, they almost certainly brought water with them. While it has long been believed that comets provided Earth’s water, isotopic checks of comets have shown many of them to have different deuterium-hydrogen ratios than Earth’s oceans.
Did Life Come from Other Stellar Systems?
To begin with, most scientists have questioned whether bacteria residing in tiny dust particles or rocks could travel vast interstellar distances, especially considering that the chances of an object from another stellar system approaching a planet within the necessary range for collision are exceedingly low. This view has changed considerably in recent years, largely due to the discovery of two interstellar objects passing through our solar system a few years ago.
This has led many scientists to consider the possibility of life not only moving between planets within the same solar system but also potentially between stellar systems.
The Current Scenario of the Panspermia Hypothesis
Since the Panspermia hypothesis was first considered a scientific explanation, it has sparked a great deal of controversy. However, recent discoveries and technological advances have shown that the Panspermia hypothesis might indeed be feasible.
Although no evidence has been disclosed to prove that life exists on other planets or stellar systems, every new discovery increases the likelihood of finding extraterrestrial life in the not-so-distant future.