Seven minutes of harrowing descent to the Red Planet occured on February 18th when NASA’s Perseverance rover — a robotic “scientist” weighing 2,260 pounds–parachuted through the tenuous Martian air, marking a new era in red planet exploration. Once at the top of the Red Planet’s atmosphere, a science-fiction movie descent began as it dropped through temperatures equivalent to the surface of the Sun, along with a supersonic parachute inflation, and the first ever autonomous guided landing on Mars delivering the biggest, heaviest, cleanest, and most sophisticated six-wheeled robotic geologist ever launched into space north of the Martian equator.
The rover touched down at the ancient Jezero Crater, a 28 mile-wide impact crater (image below) that the site of home to the remains of an ancient river delta where researchers have found deposits of hydrated silica, a mineral that’s especially good at preserving microfossils and other signs of past life.
First “Sample-Return” Mission
Once it landed, Perseverance will begin executing the first-ever “sample-return mission” –an extremely rare type of space exploration mission due to its expense—and collect and store Martian rock and soil samples, which will eventually be returned in a decade to Earth. The Rover will search for signs of ancient microbial life, which will advance NASA’s quest to explore the past habitability of Mars. The rover has a drill to collect core samples of Martian rock and soil, then store them in sealed tubes for pickup by a future mission that would ferry them back to Earth for DNA analysis.
Attached to the Perseverance Mars rover is the Mars Helicopter, the first aircraft in history to attempt power-controlled flight on another planet. The helicopter will be deployed about two-and-a-half months after Perseverance touches down.
Biotic Ping Pong?
But what, some scientists speculate, if Martian life was ferried to Earth in our ancient past more than 3.5 billion years ago, when a bombardment of meteors ricocheted around the solar system, passing material between the two fledgling planets in a Mars/Earth shuttle –a planetary game of ping pong, creating a shared genetic ancestry between the two planets.
Earth May Not be the Center of the DNA-based Universe
“Earth may not be the center of the DNA-based universe,” says Gary Ruvkun, professor of genetics at Harvard Medical School and Massachusetts General Hospital.
Galactic ‘Island Species’
The iguanas of the Galapagos Islands, observes Ruvkun in Detecting Our Martian Cousins, “have evolved many unique characteristics due to their isolation from mainland iguanas. Because they can’t swim long distances, biologists believe that the first Galapagos iguanas arrived on natural rafts made from vegetation. The same phenomenon may have happened across the ocean of space. With Some researchers speculating that life on Mars may be composed of ‘island species’ that were carried away from Earth on interplanetary meteorites. Or, suggests Ruvkun, perhaps both planets were seeded by life from an even more distant “mainland.”
Scientists have found evidence that some biologically important molecules, such as the ingredients for amino acids, are delivered by comets. And we know that around 3.5 billion years ago, meteorite impacts often kicked up rocks from the Earth’s surface and launched them into space. Martian rocks found on Earth, ALH 84001, was not heated along its journey to more than 40 degrees Celsius (104 f) and could have carried life. Microbes and/or bio-molecules, conjectures Ruvkun, may have hitched a ride on one these cosmic “rafts.”
If there was life on Mars that found in the Jezero rocks and soil, it’s not too farfetched to believe that such Martian species may share genetic roots with life on Earth. Analyzing alien DNA will require a common reference point – that is, a stretch of DNA that would likely be conserved in both Martians and Earthlings.
Common Thread –RNA Gene
In 2010, Ruvkun and his collaborators proposed that this common thread should be in the 16S ribosomal RNA gene, which is vital to the protein-making process in cells, and has regions of its sequence that have barely changed over billions of years of evolution. In fact, Ruvkun observed, short segments in the 16S ribosomal RNA sequence are exactly identical in more than 100,000 species that have so far had their ribosome genes analyzed. Any Martians that share our genetic heritage will presumably carry the 16S ribosomal RNA gene with the same conserved pieces that all of us Earthlings have.
“If you were to go and find remnants of life on Mars, which we hope to do with Perseverance rover, I would be personally surprised if they were not connected at the hip to terrestrial life,” says Erik Asphaug, a professor of planetary science at the University of Arizona.
Mars –The First Habitable
“But just looking at our own solar system, what planet was likely to be habitable first?” asks Asphaug. Almost certainly Mars, he suggests, “because Mars formed before Earth did. Early in Martian history when Mars was cooling down, Mars would have had a ‘hospitable’ environment and water long before Earth.”
“The origin of life on Earth is the biggest mystery of human beings. Scientists can have totally different points of view on the matter. Some think that life is very rare and happened only once in the Universe, while others think that life can happen on every suitable planet. If panspermia is possible, life must exist much more often than we previously thought,” says Dr. Akihiko Yamagishi, a Professor at Tokyo University of Pharmacy and Life Sciences and principal investigator of the Japanese space mission Tanpopo.
In 2018, Yamagishi and his team tested the presence of microbes in the atmosphere. Using an aircraft and scientific balloons, the researchers, found Deinococcal bacteria floating 12 km above the earth. But while Deinococcus are known to form large colonies (easily larger than one millimeter) and be resistant to environmental hazards like UV radiation, could they resist long enough in space to support the possibility of panspermia?
To answer this question, Dr. Yamagishi and the Tanpopo team, tested the survival of the radioresistant bacteria Deinococcus in space. The study, published in Frontiers in Microbiology, shows that thick aggregates[a meteorite for example] can provide sufficient protection for the survival of bacteria during several years in the harsh space environment.
“Mars tugs at the human imagination like no other planet,” wrote John Noble Wilford in Mars Beckons. It seems entirely possible that life Perseverance may discover at the ancient Jezero Crater may have been delivered to Earth billions of years ago safely buried in “mountain-sized blocks” of the Red Planet.
Image credit: NASA/JPL