“How did Life begin?” Humanity has pondered over this question for centuries. It has weighed on not only scientists, as even the common man has always been bewildered by this question. This question is probably responsible for the rising of certain fields over the course of human endeavors, including philosophy, theology, geology and maybe religion. Among the emergence of various hypothesis, conjectures, theories regarding it, none has attracted more publicity than “On the Origin of Species“ by Charles Darwin, which establishes evolution as an aspect for our emergence on the Earth. Many creationists over the past decades have tried to challenge the theory of evolution, but the analogy given by Sir Charles Darwin has been indisputable.
According to his theory, the humans and myriad of other species that inhabit present Earth have evolved over the course of generations on the basis of natural selection. The organisms that survived had formed certain traits that gave them an advantage over others which made them ‘fit for survival’ and hence ensured their species’ emergence.
On the aspect of origin, Darwin discussed the suggestion that the original spark of life may have begun in a “warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity and that a protein compound was chemically formed ready to undergo still more complex changes.” This bold statement popularized at the time, yet was heavily ridiculed and criticized.
The proportionate theory given by Darwin was later somewhat supported through varied scientific experiments, including the concrete ‘Miley-Urey Experiment’.
Among the numerous disparate theories regarding our emergence, one other theory has also garnered a similar response, titled ‘Panspermia’. This theory is similar to The Theory of Evolution on the grounds that is not meant to address ‘how life began’, just the method of how it may have spread over the universe. According to Panspermia Hypothesis, the seeds of life exist all over the universe and can be propagated through space from one location to another.
Supporters of this hypothesis can be found throughout history. One of the foremost individual advocates being the Greek philosopher Anaxagoras (500-428 B.C.) who asserted the basis of the hypothesis itself. Over centuries, this theory lost momentum due to the lack of any validation and remained merely speculative. However, with recent advancements in space science research and astrobiology, The Panspermia Hypothesis could be tested experimentally and a variety of studies from the different field of research has been performed. This interest was revived in the late 70s by the recognition of Martian meteorites here on Earth which proves beyond doubt that intact rocks can be transferred between the surfaces of planetary bodies in the Solar System.
Considering the ecological degradation of Earth, scientists have started considering Panspermia as a mean to initiate life on other lifeless planets and have named the process Direct Panspermia. Life on Earth is vulnerable and limited, but life in multiple worlds will be secure and virtually limitless. The objectives of directed panspermia are to assure that the gene/protein form of life will continue and to maximize life in the accessible universe. No one can predict how long our technological civilization will exist but we must secure and promote life while we are sure that we can. Panspermia missions can assure that life will exist throughout the nearby galaxy.
Can Life Survive on Asteroids and Comets?
We can answer these questions by measuring the nutrient contents in Mars, asteroid meteorites, and the growing living organisms on them. From these studies, we can find out how much biomass each kilogram of the asteroid and similar cometary materials can support.
An early observation that carbonaceous chondrite materials can support life was made in the 1870’s by a Swedish traveler, Dr. Berggren, in Greenland. He observed that black cryoconite dust on the snow was inhabited by cyanobacteria.
Laboratory studies of these interactions started with a chance observation on the Murchison meteorite. Professor David Deamer, a membrane biophysicist, found in 1985 that some components extracted from the Murchison meteorite can form membrane-bound vesicles whose shapes resemble cells. The amphiphilic components that form the vesicles also form a foam when the extracts are shaken in a test-tube. They kept such a solution in a vial and noticed that after a few weeks it stopped forming a foam. This indicated that the surface-active materials might have been metabolized by microorganisms, suggesting that the Murchison extracts support microorganisms.
DIRECT PANSPERMIA: TECHNICAL ASPECT
In proposals of directed panspermia there are two major types of targets:
(a.) The first target may be planetary systems that are relatively close, say within 50 light-years from the sun. Major efforts are underway to find solar systems with Earth-like habitable planets. If they are found we can check whether they harbor life by looking for telltale gases such as oxygen and methane in their atmospheres, and for the green color of chlorophyll on their surfaces. If we find planets that are habitable but uninhabited, they would be prime targets to seed with life by panspermia missions
(b.) The second type of target is the star-forming zones in interstellar clouds. These are areas of relatively dense gas and dust which form new stars, their planets, asteroids, and comets. These star-forming zones are large and can be reached with less precise targeting. In addition, each such zone typically forms 50 – 100 new solar systems simultaneously, which increases the chances that some will have habitable environments in which the panspermia payloads may be captured
Speed is a critical factor because we are aiming at moving stars and interstellar clouds, and their positions become increasingly uncertain with time. Also, long exposure to space radiation degrades the biological payload. At the realistic speed of 10-4 c, a solar system 10 ly (light-years) away will be reached in 100,000 years, and an interstellar cloud 100 ly away will be reached in 1 million years, well past the lifetimes of the senders and possibly of their civilization. Advanced technologies such as nuclear or ion drives and even anti matter drives may later reach speeds of 0.1 c, reducing the travel times by a factor of 1,000, but it is uncertain if these can ever be realized.
3. Biological Payloads
It must include a variety of organisms, ensuring that some will survive in the diverse and extreme environments whose conditions cannot be predicted accurately. They must include algae that can develop into plants to support higher life. They must also include eukaryotes and small multicellular organisms that can evolve into animals and intelligent life forms. In this respect we are aiming to reproduce terrestrial evolution, while we recognize that on diverse targets, evolution may follow different paths to promote this purpose, panspermia missions with diverse biological payloads will maximize survival at the targets and induce evolutionary pressures. In particular, eukaryotes and simple multicellular organisms in the payload will accelerate higher evolution. Based on the geometries and masses of star-forming regions, the 1E24 kg carbon resources of one solar system, applied during its 5E9 yr lifespan, can see all newly forming planetary systems in the galaxy.
As discussed above, we are looking primarily at methods to propel the panspermia missions that are relatively simple, based on known technology, feasible on a modest scale, and inexpensive. These criteria would seem to be difficult to satisfy for interstellar missions, but solar sailing can do so. Solar sailing is based on radiation pressure. When photons from the Sun recoil from a reflecting surface, they impart forward momentum to the surface. Under this pressure, the object accelerates slowly but steadily, building up speed away from the sun
Petrographic analysis of the Martian meteorites demonstrated that these rocks experienced heat in the range 40ºC to 350ºC and acceleration of 3.8 x 106 m/s. As discussed above, we are looking primarily at methods to propel the panspermia missions that are relatively simple, based on known technology, feasible on a modest scale, and inexpensive. These criteria would seem to be difficult to satisfy for interstellar missions, but solar sailing can do so. Solar sailing is based on radiation pressure. When photons from the Sun recoil from a reflecting surface, they impart forward momentum to the surface. Under this pressure, the object accelerates slowly but steadily, building up speed away from the Sun. Based on these data, mechanisms for the transfer of planetary material have been proposed.
The most well-accepted mechanism indicates that materials can be expelled into interplanetary space under modest temperature increases. In fact, recent measurements in the Martian meteorite ALH84001 have shown that it was probably not heated over 40ºC before it was ejected from Mars. These results led to the question whether living organisms have been transported between the planets by the same mechanism. The viable transfer from one planet to another requires microorganisms to survive the escape process from one planet, the journey through space, and the re-entry/ impact process on another planet. In this context, a variety of studies has been performed in order to simulate different aspects of panspermia.
Once the payload has been propelled to the target planetary system, it all leads down to deceleration of the payload on the system and its growth on the planet itself. Eventually, the evolution of the target species could give rise to a genetical preservation of our human race on another planet. Hopefully, we might be able to achieve and replicate the same process that gave us life.
We know that life exists on Earth, but its future here is finite and uncertain. We understand that life is unique and precious. We know that we can now plant our family of life in other solar systems where other intelligent beings may evolve who will further promote life in the galaxy. We are a force of nature that can expand life in the universe. We are impelled to do so by the patterns of life imprinted in our very being. If we advance life, our human existence will acquire a cosmic purpose. Directed Panspermia will fulfill our human purpose of securing and expanding the family of organic life in the universe.
Edited by: Kaylynn Crawford and Shreya Singireddy