Will We Recognize Life on Mars When We See It?

Percival Lowell was not the initially to think he’d discovered existence on Mars, but he was amid the final. In the late 19th and early 20th centuries, the American astronomer posted a collection of books marketing his idea that observable characteristics on the floor of the Pink World were being the handiwork of an intelligent species on the verge of extinction. The objects of Lowell’s fascination—and the wider astronomy community’s scorn—were the so-known as “Martian canals,” which he thought were being employed to route h2o from the planet’s ice caps.

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NASA has been robotically discovering Mars given that the mid-’60s, and due to the fact of these missions we’re now relatively specified that the earth isn’t house to any extraterrestrial engineers. (Sorry, Percy.) But these spacecraft did obtain an abundance of geological proof that Mars may well the moment have had liquid h2o on its floor, a magnetic area, and a thick environment, which leading the record in terms of stipulations for existence as we know it. In other text, there’s continue to a prospect that standard existence kinds the moment existed on the floor of the Pink World. And later this thirty day period, NASA will consider its greatest phase nevertheless towards acquiring out.

On July 30, NASA is anticipated to start its new rover, Perseverance, on a 1-way journey to Mars. The car-sized robotic geologist will commit its initially yr on the earth drilling core samples in search of indicators of historic existence. (An additional robotic mission later this decade will return the samples to Earth.) The rover will collect at least 20 tubes of filth all around its landing web page, the Jezero crater, which scientists believe was a river delta approximately 4 billion a long time in the past. If Mars ever hosted existence, the stagnant h2o of the historic Jezero delta would be the style of position you’d hope to obtain it.

But never hope Perseverance to dredge up any bones or seashells—it’s on the hunt for fossilized microbes, not mollusks. And even acquiring an intact bacterium would be an astonishing stroke of luck. “That would be a complete desire,” suggests Tanja Bosak, an experimental geobiologist at MIT and a member of the ten-individual group that will guide the rover’s sample range. As a substitute, the rover is looking for probable biosignatures, the faint molecular traces left at the rear of by microbes billions of a long time in the past. If Perseverance discovers existence on Mars, it will be considerably less like encountering a stranger in the woods and extra like getting their footprints.

When she’s not searching for historic existence on other planets, Bosak studies the earliest existence on our possess, a course of action she suggests is analogous to what Perseverance will be performing on Mars. To keep track of down historic microbes on Earth, geobiologists seem for patterns in rock formations that could only have been shaped by biological procedures. Stromatolites, for example, are rocks infused with levels of what Bosak phone calls “organic gunk.” These slim sheets of fossilized algae and other primitive organisms form sediments in a unique wavy pattern that is seen to the naked eye.

“With microbes, you never truly see only a one cell. It’s constantly a macroscopic group,” suggests Bosak. “The basic interactions in between natural issue and minerals ought to be the identical on Earth and Mars, so we’ll use cameras to seem for these diverse kinds of microbial styles.”

It would be a major offer if Perseverance finds stromatolites on Mars, but not sufficient to establish the existence of extraterrestrial microbes. The rover would also have to obtain an abundance of molecules that are commonly linked with existence in the identical spot. “All cells metabolize,” suggests Bosak. “They consider in molecules from the setting and spew out something else.” This could include things like standard things like phosphorus and nitrogen, or extra complicated natural molecules like calcium carbonate. In a ideal case situation, the rover would obtain fossilized traces of lipids or other biomolecules that are essential for living matters. The challenge for Perseverance will be acquiring these fossilized molecules smeared across a mote of Martian dust.