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5 days ago · The fact that a small (about 4-pound) meteorite from a planet contains large numbers of bacteria suggests that such bacteria were widespread on the surface of Mars, the researchers say. A stone of similar size from Earth would contain many bacteria.
Sep 8, 2021 · Yes, it is possible for microorganisms to survive the journey from Earth to Mars. That’s why we have a program specifically dedicated to ensuring the spacecraft is as clean as possible before leaving Earth—if we ever detect life on Mars, we are certain that it did not come from our own planet.
Aug 26, 2020 · If so, then a bacterial colony could theoretically survive the journey from Earth to Mars, and vice versa, which would take several months or years cruising through outer space.
- Passant Rabie
- Overview
- A temperate Mars of the past
- Hardy microbes
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 fissures, 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 short-lived 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 appearing 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.
Dry and irradiated, the Martian surface would challenge even the hardiest of Earth’s microbes to survive for more than a moment.
Billions of years ago, though, the planet was warmer and more watery. It’s not clear how long those temperate conditions persisted or exactly how much water there was, but it is clear that ancient Mars contained all the ingredients for life as we know it, including water, carbon-containing organic compounds, and active chemical reactions that provide energy.
Which is why Sauterey, a computational ecologist, decided to see just how habitable early Mars might have been. Previously, his team developed models to characterize how Earth’s early life influenced the planet’s surface conditions some 3.5 billion years ago, when Mars may have been habitable as well.
As described in a paper published in Nature Astronomy, Sauterey and his colleagues considered multiple models of Mars with different atmospheres, surface temperatures, and types of brine, which have different freezing points. They assumed that any organisms populating the planet would have been the sort of hydrogen-gobbling, methane-producing microbes that also populated early Earth—and they assumed that such microbes would be limited to environments at least 10 feet beneath the Martian surface, where life-sustaining brines are plentiful and radiation is not.
The team found that both surface temperature and the type of brine play a crucial role in determining the likelihood of habitability. In the team’s simulations, habitable subsurface environments were less likely to exist on a colder, more ice-covered planet because glaciers limit the amount of hydrogen gas that can reach the subsurface to fuel alien metabolisms. But on a warmer and less icy world—in its most life-friendly form—Sauterey found there was at least a 50 percent chance that swaths of the shallow subsurface were habitable billions of years ago.
“Our result is that Mars, if it was not fully ice-covered, was likely habitable,” he says. “That does not mean it was probably inhabited, because we don’t know how you switch from habitability to inhabitation.”
Another team of researchers approached the question of Martian life in a different way: by seeing how long microbes could survive in conditions mimicking those roughly 30 feet beneath the surface. At that depth, the level of incoming solar and cosmic radiation is about the same as the dose sustained on Earth’s surface—but the soils are frozen and dry.
The team chose to study a bacterium called Deinococcus radiodurans—one of the most famous extremophiles, known for its ability to withstand immense doses of radiation. Found in nuclear reactors as well as Antarctic soils, D. radiodurans survives by quickly repairing radiation damage to its DNA.
“The fact that we have these things on Earth—the fact that radiodurans is found in nuclear reactors—is crazy. We didn’t have [reactors] until not even a hundred years ago,” says the University of Florida’s Williams, who was not involved in the new research.
In liquid culture, D. radiodurans can survive a dose of approximately 25,000 Gray (Gy); in contrast, just 5 Gy will kill humans and most other vertebrates.
The team studying D. radiodurans found a way to make the critter even more extreme, as described in a study published in the journal Astrobiology. First they dried out a culture of D. radiodurans. Then they froze it, mimicking the cold, desiccated state beneath Mars—which caused the culture to enter a dormant state. When they challenged the sleeping bacteria with increasing doses of radiation, they found that cells in suspended animation could withstand a dose of approximately 140,000 Gy.
“That’s really an enormously big number; it’s astronomical,” says lead researcher Michael Daly of the Uniformed Services University in Maryland. “One would expect that microorganisms that evolved on Mars are as resistant—if not more resistant—to radiation than D. radiodurans, which evolved on a relatively mild planet called Earth.”
Aug 26, 2020 · Space 26 August 2020. By Carly Cassella. (Caleb Betteridge/Moment/Getty Images) What if microbes could drift through the vastness of space like pollen in the wind, planting the seeds of life on planets both far and wide? Is that how life started on our own planet? Is such a journey even possible?
Feb 23, 2021 · CNN — The surface of Mars is a harsh frozen desert, but some microbes from Earth could temporarily survive there, according to a new study. And the researchers didn’t even have to send...
Oct 10, 2022 · According to the study, simple microbes that feed on hydrogen and excrete methane could have thrived on Mars some 3.7 billion years ago, at about the same time that primitive life was taking...
