In 1877, the Italian astronomer Giovani Schiaparelli conducted an exhaustive and detailed observation of the surface of Mars.
He described huge streaks across the surface, which he called canali or "channels." In English, the word was incorrectly translated as "canals," and compared to the recently-built Suez Canal. This set off what would be a long and unabated fixation on the possibility of life on the Red Planet.
NASA's recent discovery of water on Mars has rekindled hopes that we may yet find neighbors in our solar system. But other things we've learned about Mars — and particularly ancient Mars — give us clues suggesting we should consider the possibility that we have already discovered Martian life. They might also hold important implications for the most enduring mystery in science, the origin of life.
In recent years, the idea that life on Earth may have first arisen elsewhere — before migrating to our planet — has gained some traction. The theory is called "panspermia," Greek for "life everywhere," the name given it by the ancient philosopher Anaxagoras. It became particularly popular during the 19th century, partly because it explained some gaps in Darwin's concept of evolution. The evolution of complex creatures, such as human beings, through natural selection was thought to require at least hundreds of millions of years. Such a timeframe was difficult to reconcile with 19th century estimates of the Earth's age, something usually then measured in the tens of millions. Panspermia solved that problem — and two of the most accomplished scientists of the age became key proponents, the Swedish chemist Svante Arrhenius, director of the Nobel Institute, and Lord Kelvin, who was instrumental in formulating the theory of thermodynamics.
In the 20th century, when the age of the Earth no longer presented an obstacle to Darwin's theory of evolution, the theory slipped into the fringes of science. It was resurrected a few times, but without a lot of success. The astronomers Fred Hoyle — who coined the term "Big Bang" — and Chandra Wickramsinge proposed that life began in an outer space and was first transported to Earth via meteorites. Later, Francis Crick — frustrated by the inability to make progress on the question of the origin of life — half-seriously co-authored a book arguing that life was seeded on Earth by aliens. Neither Hoyle and Wickramsinge nor Crick gained much traction.
But in the years since — and particularly the last decade — panspermia has gradually made a comeback among scientists in search of the origin of life. At the very least, scientists have come to accept the idea that some early stages of the long, complex beginning of life took place outside the Earth.
Wickramsinge's hypothesis that the vast clouds of cosmic dust that fill space are filled with organic matter has since been proven true. The world's best-known origin-of-life scientist, Harvard's Jack Szostack, has constructed a model under the assumption that the first organics that led to life may well have been extraterrestrial.
The formation of organics, though, has always been the relatively easy part of the mystery of the emergence of life. The part that has long baffled scientists is getting from there to an actual organism. Mars may hold answers there, as well.
The most important findings of the Mars Rover may not be that water exists on the planet now, but that it held standing water in the past. Rover found proof that Mars contained lakes, rivers and deltas that could have been key incubators for life. Among some who subscribe to the theory of the RNA World, which holds that the earliest life was composed of little-more than a strand of RNA, Mars could even have been a better incubator than the Earth.
One of the more prominent advocates of Mars-based origin theory is chemist Steven Benner, a founder of the Westheimer Institute at the Foundation for Applied Molecular Evolution in Gainesville, Florida. Like others working with an RNA World model, Benner's goal has been to find a pathway from simple organics to a simple organism of self-replicating RNA, something that has proven exceedingly difficult under conditions likely found in the early Earth. But Benner has discovered that the binding of organics into rudimentary RNA can be eased by the presence of borate and molybdate. Oxygen would be required for the compounds to form, and our planet had none until the advent of life. Neither was likely present in the early Earth. However, the atmosphere of ancient Mars likely contained oxygen, and the planet could well have had ample supplies of borate and molybdate.
If life did arise on Mars, the trek to Earth might not have been that difficult, or implausible. Modern tests have shown that microbes could survive such a journey on a meteorite, reviving the old panspermia image of living microorganisms hurling through space. Benner's theory still has a wealth of detractors, but it has become a very enticing explanation for a mystery that continues to baffle scientists. A Mars-based origin could also explain why life's advent has proved so elusive to scientists. They may have been looking in the wrong place all along, and at the wrong conditions.
So, as we continue to hunt for Martians on Mars, perhaps we should consider the possibility that we've already found them — and that they are us.
Bill Mesler is co-author of A Brief History of Creation: Science and the Search for the Origin of Life, which will be published by Norton in December.
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