The possibility of life arising on Mars and then getting transferred to Earth through meteorite bombardment is a possible and perhaps a highly probable scenario, according to latest research.
Forget the green little beings with antennae on their head and the menacing greys which abduct people and the greyer granular videos claiming to be of unidentified flying objects (UFOs). Parallel to the fantasy-driven UFO-seekers, whose aliens and UFOs have more to do with their own minds than aliens out there, there has always been a serious quest for extra-terrestrial intelligence.
Search for extra terrestrial intelligence or SETI has been, for decades, one of the popular science projects and contrary to what one hears about secrecy surrounding such ventures, the SETI project is one in which the computational powers of the vast network of humans using web-linked computers has been used to search the cosmic signals for potential SETI candidates. No secrecy at all!
Apart from SETI, there are many labs around the world which have been hunting for signs of life on other planets. They have been scanning not only the planets but also satellites of planets like Jupiter and Saturn for tell tale signs of life — particularly microbial life.
On all these fronts we have had candidates for decades.
The way science looks for alien life is by first trying to rule out its possibility. Mostly, natural explanations are sought for an observed phenomenon and only if all such possibilities are exhausted the alien explanation is accepted.
This should be understood as necessary. Easy acceptance of the alien hypothesis would have actually damaged and slowed our understanding of the universe — just like the ‘God did it’ stand.
Yet, we have been seeing candidates pop up now and generate excitement within the scientific community and media.
Consider for example ALH84001, a Martian meteorite fragment that was discovered in Antarctica in 1984.
In 1996, geologist and then chief astrobiologist for NASA published a paper with his team that argued that the meteorite fragment contained in it fossilised proof of microbial life — probably Martian. This generated quite a strong interest in exobiology.
There were polycyclic aromatic hydrocarbons (or PAH) found on the fragments. These are essential building blocks of life. They have also been detected in interstellar dust.
Then there were nanostructures which looked like fossilised remains of bacterial activity. At that time, it held up the tantalising possibility that the meteorite contained fossils of microbial activity.
Since then, many solar winds have generated many auroras. And many meteorite showers have happened.
In 2017, a team of researchers discovered that chemicals have the capacity for self-organisation into structures that can deceivingly look like remains of ancient microbial life forms.
Calcium or barium salts in primordial waters, reminiscent of primitive earth conditions, generated very small structures including tunnels resembling microbial activity.
So, these structures by themselves cannot be considered as proof of existence of Martian microbial fossils, carried to earth on a meteorite.
Most important of all the evidence then considered as a clear signature of life was the magnetite crystals on the meteorite.
Almost one quarter of the magnetite crystals embedded in the meteorite fragment were thought to be of biological origin. These crystals resemble the magnetosomes more, unique crystalline nanoparticles found in magnetotactic bacteria.
These are bacteria that use the magnetic dipole formed by the magnetosomes to orient themselves in relation to the planet’s magnetic field.
Here too, with deeper study, there came a twist.
The characteristics of the magnetite crystals found in the Martian meteorite, which were thought to be of biogenic nature, were later attributed by scientists to ‘an exclusively inorganic origin’.
When scientists tried an inorganic process that mimicked what should have been the Martian process that resulted in the formation of magnetite from iron rich carbonate, they were able to get magnetites that resembled what was thought to be the biogenic magnetites of ALH84001.
Yet, the case for ancient microbial Martian life is not all lost. In fact, it has found some renewed interest.
Christopher Carr, a scientist associated with the Georgia Institute of Technology has argued for a Martian origin of life on earth in his recent paper.
Scientists consider what are called cyanosulfidic compounds as precursors of the present vital and basic bio-chemical components of life. They are considered as precursors for quite a number of amino-acids the building blocks of proteins, lipids — which are important in forming membranes needed for life organisation and for a family of nucleotides called pyrimidines.
This family of nucleotides have in them a uracil and nitrogen base unique to RNA.
The planetary scenario in Mars, compared to the same scenario on Earth, was more favourable to the emergence of the basic components of life. Earth was more of a water world.
But the Martian surface then faced ‘ultraviolet light, wet-dry cycling, and volcanism’, points out Carr.
It is a well-known fact that the transformation of earth into an oxygen-rich planet was a crucial step in the evolution of life.
Oxygen got embedded in the atmosphere of the earth 2.45 billion years ago and it was at least 300 million years ago that oxygen started getting produced on the planet.
The cyanobacteria contributed to this oxygen production. According to Carr, "the timing of the rise of oxygen on Earth is inconsistent with final fixation of the genetic code in response to oxidative stress”.
The possibility of life arising on Mars and then getting transferred to Earth through meteorite bombardment is a possible and perhaps a highly probable scenario, according to Carr.
He also puts forth the possibility of a life-tree evolving with RNA->Protein process instead of the DNA->RNA->Protein process that is almost universal here on Earth.
It is an exciting scenario indeed that life formed on Mars and got transplanted to Earth and became enriched with infinite variation. The canvas of life has became larger and its mystery deeper.
Panspermia within the solar system is no more a wild speculation but nearing the status of a respected hypothesis that will be soon tested.
And on 18 February 2021, NASA’s Perseverance rover landed on Mars. The landing site was a crater measuring 49 km in diameter called Jezero Crater. The spot is geologically interesting because once upon a time in the planet's history, almost 3.5 billion years ago, this was filled with water.
If Martian microbes existed, then this place would be a good candidate to look for them. The rover is equipped to do activities that will soon reveal to us how life existed on Mars, if it existed at all.
And with that comes the even more astonishing possibility of the ‘Out of Mars’ theory becoming a reality.
Journal reference: Christopher E Carr, Resolving the History of Life on Earth by Seeking Life As We Know It on Mars.
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