Life just might exist on Mars after all

    The red planet may have once been home to an abundance of microbes. New studies suggest it's possible that some hardy microbes managed to survive underground in a frozen state.

    About 3.5 billion years ago, two of the planets that orbited the sun may have had biospheres of similar bulk. One, Earth, evolved in a way that allowed life to flourish and splinter into endless forms most beautiful. Mars, the other world, followed a different path.

    Today the Martian surface is hostile to life as we know it, but as this scientific story goes, Mars may have once hosted a rich abundance of microbes. Residing in the planet’s briny underworld and shielded from the lethal radiation that bathes the surface, these organisms could have grown in nooks and ____________, multiplying until their collective heft rivaled Earth’s cache of life. Called methanogens, Mars’s microbes would have inhaled atmospheric hydrogen and carbon dioxide and exhaled methane gas - and in a twist, they may have turned out to be their own worst enemy.

    Over time, their growing, insatiable appetite would have robbed the Martian atmosphere of hydrogen - a powerful greenhouse gas during the planet’s early days - ultimately casting a deadly freeze over the planet and driving microbial populations into deeper, warmer crannies. How long those burrowing microbes could have survived in the deep is unknown. It’s possible they were only a shortlived flash of life on an otherwise sterile world.

    “Maybe extinction is the cosmic default of life in the universe,” says Boris Sauterey of the Institut de Biologie de l’Ecole Normale Supérieure in Paris. “It’s not the process of life ____________ that is limiting; it’s life maintaining itself that is limiting.”

    But perhaps, more than 30 feet beneath the surface and encased in ice, these ancient single-celled organisms achieved a state of dormancy - a sort of cryopreserved slumber, ready to perk up when more life-friendly conditions arise.

    The Martian interior may not be as lifeless as its face. It could host a world of alien organisms that are capable of waiting thousands of years between each turn of their metabolic engines.

    This ____________ may sound farfetched, but recent results from scientists modeling the habitability of ancient Mars and studying the hardiness of microbes in labs and beneath our own planet’s surface all point in the same direction: It’s a long shot, but it’s possible life evolved on Mars and still exists. And scientists may just find signs of that life when meteors barrel into Mars and excavate buried layers of ice, or when new spacecraft arrive to plumb this underground realm.

(Fonte: National Geographic - adaptado.)