Has Nasa Already Found Life On Mars?

On July 20, 1976, NASA’s Viking 1 lander became nan first spacecraft to safely touch down connected Mars. Shortly after, it beamed backmost our first close-up image of nan surface—a drab position of pebbles strewn astatine nan lander’s feet.

“I don’t deliberation we’d person been amazed if location were blades of grass,” recalls Tom Young, Viking’s ngo director. Scientists had speculated for years astir what scenes would await Viking 1 and its twin, Viking 2, which landed elsewhere connected Mars a fewer weeks later. Most thought immoderate Martians would, astatine most, beryllium simple, mini life-forms—although Carl Sagan had impishly suggested that polar-bear-sized creatures could populate nan landscape.

Humans person imagined different inhabited worlds for millennia. And we’ve moreover “discovered” life connected Mars much than erstwhile crossed nan last century aliases two. Yet each clip we’ve built sharper devices and taken a person look, each those claims person evaporated, overmuch for illustration nan Red Planet’s ancient seas. By nan clip nan Viking landers launched, we knew location were nary signs of life that could beryllium seen from orbit.

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But location was still dream that possibly thing stirred there—hope capable to motorboat nan Viking landers connected an audacious ngo to look for it. Their results, however, weren’t conclusive. Most experts work together nan copy spacecraft grounded to find definitive signs of organisms successful scoops of Martian soil, but immoderate scientists proceed to judge they did.

A representation of nan satellite Mars and its putative “canals,” produced by nan astronomer Percival Lowell for nan October 1894 rumor of Scientific American.

Scientific American

Even now, a half-century later, nan result of those investigations fuels debate, and nan Viking landers stay nan only missions ever sent to nan aboveground of different world to hunt for extant alien life. The ambiguity that wafted from their ungraded samples has go emblematic of nan uncertainty that plagues nan greater hunt for extraterrestrial life—not conscionable connected Mars and our sun’s different worlds but crossed nan observable universe. Our knowledge of life’s beingness limits and nan unearthly forms it mightiness return remains truthful incomplete that we could each excessively easy state a find wherever nary genuinely exists—or neglect to admit genuine extraterrestrial biology hidden successful plain view.

As a result, astrobiologists have, for decades, defaulted to a blimpish load of impervious that leans into 2 aphorisms coined by Sagan erstwhile he wasn’t musing astir Martian polar bears: life, he and his co-authors wrote, should beryllium considered a “hypothesis of past resort,” mostly because “extraordinary claims require bonzer evidence.”

Carl Sagan stands successful beforehand of a Viking lander exemplary successful Death Valley, California.

NASA/JPL

But what if Sagan had it each wrong? If we unrecorded successful a beingness wherever life is communal and not bonzer astatine all, mounting specified an extraordinarily precocious barroom for its find beyond Earth tin backfire. What if life’s fingerprints person been connected Mars each along, and we were excessively cautious to admit that we’d recovered them?

Already, a increasing heap of grounds suggests ancient Mars could very good person been an inhabited planet—and whitethorn still be. Our hunt for life location is simply a spot for illustration bobbing for apples blindfolded—except we don’t cognize what an “apple” mightiness consciousness like, and nan apples whitethorn beryllium only successful scattered pieces. What’s needed, galore scientists argue, is simply a clearer measurement of separating signs of “life” from “nonlife,” a quantitative method that leverages statistic and probabilities to guideline our interpretations of biology’s imaginable fingerprints.

“There’s each these different lines of grounds that support coming together that make maine go, ‘Gosh, it’s becoming much and much difficult to explicate everything connected Mars abiotically,’” says Amy Williams, an astrobiologist astatine nan University of Florida. “I’m not yet fresh to opportunity that we’ve recovered grounds for life, but I deliberation nan communicative is building to thief america understand what that imaginable is —to put a probability connected that alternatively of conscionable saying ‘yes’ aliases ‘no.’”

Present-day Mars is marginally habitable astatine best, but 3.5 cardinal years agone nan satellite was almost surely a much life-friendly world. Ancient Mars was warmer, pinch a thicker ambiance and a world magnetic section that protected its aboveground from cosmic radiation; seas and lakes filled its basins, and rivers tumbled done its valleys. Over eons, Mars mislaid its magnetic section and, pinch it, those bodies of h2o and thick, insulating atmosphere.

An artist’s conception of an water successful nan bluish hemisphere of Mars, from billions of years agone erstwhile nan satellite was warmer, wetter and presumably much habitable than it is today.

NASA’s Goddard Space Flight Center

Yet crossed nan expanse of Mars’s lifetime, integrated compounds—life’s building blocks—have rained down connected nan planet, delivered by meteorites and cosmic dust.

“If we unrecorded successful a beingness wherever life takes advantage of watery environments erstwhile there’s juicy chemistry going on—which is nan measurement I image nan universe, but that’s unvalidated intuition—then thing should person started happening successful immoderate of those places connected Mars,” says astrobiologist David Grinspoon of nan Planetary Science Institute. “So there’s this predisposition to think, ‘Either location should person been an root of life connected Mars—or we’re really incorrect astir thing connected Earth.’”

Since 2012 NASA’s Curiosity rover has been searching for signs of ancient habitable environments successful Gale Crater. And successful 2021 nan agency’s Perseverance rover touched down successful Jezero Crater pinch nan extremity of looking specifically for ancient biosignatures, not present-day life. Now, based connected nan results of those robotic explorations, galore experts fishy that ancient Mars was so a biologic world, moreover if they can’t yet beryllium it.

“The grounds for habitable environments and life connected early Mars is getting stronger each clip we look astatine it,” says Chris McKay, an astrobiologist astatine NASA’s Ames Research Center.

The astir compelling hint comes via a reddish mudstone recovered by Perseverance that’s dappled pinch “leopard spots,” aliases mineral assemblages that incorporate chemically altered robust and organics. Such spots connected Earth rocks are usually nan activity of mineral-munching microbes. In fact, scientists haven’t yet recovered a convincing measurement to explicate nan study connected Mars without biology; for specified chemistry to hap without life, it seems, nan stone would’ve had to acquisition a group of events aliases conditions that look alternatively improbable, fixed our existent knowing of its history and environment.

From rocks scattered astir Gale Crater, Curiosity contributed different intriguing observation: a peculiar abundance of long-chain alkanes, carbon-containing molecules that, connected Earth, sometimes originate from fatty acids specified arsenic those successful compartment membranes. Scientists deliberation the Martian chains are fragments of larger fatty acids that were degraded agelong agone by cosmic radiation and then, overmuch later, by nan instrumentality connected Curiosity that studied them. If so, Williams says, nan original molecules would person been difficult for abiotic sources, specified arsenic meteorites, to deliver; nan longest of nan fatty acids would beryllium longer than thing yet recovered successful meteorites.

While not definitive, those observations from Mars are surely exciting. “It’s what you mightiness telephone permissive grounds of life—it could beryllium that microbes near down this material,” McKay says. “But it’s not persuasive.”

Potentially microbe-made mini acheronian “poppy seed” speckles and larger dark-rimmed “leopard spot” blobs dot nan aboveground of “Cheyava Falls,” 1 of nan astir intriguing rocks ever recovered connected Mars.

NASA/JPL-Caltech/MSSS

To definitively reply nan mobility of whether those molecules carnivore biology’s fingerprints, scientists first request to norm retired each imaginable abiotic explanation—an endeavor that requires a afloat knowing of a imaginable biosignature’s biology context. That’s difficult capable to do connected this planet, and it’s moreover harder to execute remotely.

Or we could bring samples from Mars to study successful labs present connected Earth. NASA had been readying to usage its Mars Sample Return ngo to retrieve pieces of nan leopard-spotted stone and different prime Perseverance-collected specimens, but nan scheme grew truthful analyzable and costly that Congress defunded it. Astrobiologists still dream nan samples will yet find a cheaper, much workable measurement backmost to Earth.

The hunt for life beyond Earth should beryllium nan agency’s highest priority, Young says. And nan enigma of our seeming cosmic solitude could beryllium solved by a cache connected rocks that are conscionable waiting for retrieval connected Mars.

“I deliberation that’s really important for america to do,” he says. “Every leader who passes connected nan opportunity to bring those samples backmost has put a acheronian people connected their leadership.”

Until—or unless—Mars Sample Return happens, astrobiologists are forced to wrestle pinch what, exactly, would make a imaginable biosignature “persuasive.” Sure, we tin each ideate a fewer scenarios successful which impervious of extraterrestrial life would beryllium unequivocal: premier numbers encoded successful a power transmission, a fossilized trilobite connected Mars, squidlike aliens successful nan outer star system’s water moons.

When it comes to ancient Mars, however, astir experts don’t expect to find “one portion of data, and now we cognize nan answer,” says Rebecca McCauley Rench, NASA’s lead intelligence for astrobiology successful planetary sciences.

But if ringing nan “alien life” doorbell will apt trust connected a preponderance of grounds alternatively than immoderate singular, slam-dunk observation, wouldn’t astrobiologists do amended to wantonness Sagan’s aphorisms?

“‘Extraordinary claims require bonzer evidence’ is a pithy slogan, but it’s benignant of limiting,” says Christopher House, an astrobiologist astatine Pennsylvania State University. In deference to Sagan’s credo, he says, “people will crook complete backward to opportunity that immoderate they’ve recovered is abiotic.” Instead, House suggests, scientists should see explanations that invoke life pinch nan aforesaid rigor and sincerity pinch which they measure abiotic conclusions.

Plus, chemist Steven Benner says, “what’s ‘extraordinary’ arsenic a declare depends connected who is perceiving it.” If it’s not truthful crazy to ideate that ancient Mars was a biologic world, past possibly “life” isn’t specified an bonzer declare aft all.

“What if we unrecorded successful a beingness wherever life is very ordinary?” asks Michael Wong, an astrobiologist astatine Carnegie Science. “If we only fto something’s rareness guideline america to life, we whitethorn miss a batch of life that is conscionable mean life, and we whitethorn beryllium drawn to bonzer nonbiological processes and deliberation they’re life instead.”

To reason thing pinch assurance from a group of “ordinary” observations, scientists request to build a quantitative measurement to find whether a group of observations are a signature of biology. “That quantitative biosignature study should beryllium a extremity wrong nan community,” says astrobiologist David Catling of nan University of Washington, “because different it’s each conscionable hand-waving, and we’re not making immoderate definitive answers. It’s still interesting, and discoveries ever move things forward, but we person to beryllium much quantitative astir it.”

NASA’s Perseverance Mars rover took this selfie, made up of 62 individual images, connected July 23, 2024. A stone nicknamed “Cheyava Falls,” which bears tantalizing features suggesting it whitethorn incorporate ancient microbial fossils, is to nan near of nan rover adjacent nan halfway of nan image.

NASA/JPL-Caltech/MSSS

Say you person 100 Mars rovers poking astir successful various craters, and each of them finds thing for illustration nan leopard spots aliases those long-chain alkanes. You do nan activity to norm retired earth science and recognize that while you could explicate nan observations without invoking biology, those explanations each require conditions aliases processes that are improbable. Or maybe, says Morgan Cable, a planetary intelligence astatine Victoria University of Wellington successful New Zealand, you do each that activity and extremity up uncovering abiotic explanations that are mutually exclusive.

“When do we get complete nan period to say, ‘Yeah, nan likelihood of america uncovering this galore imaginable biosignatures intends we tin region nan connection potential’?” Cable says. “It’s almost for illustration we person to return Carl Sagan’s ‘hypothesis of past resort’ and use that to nan abiotic lawsuit arsenic well.”

For immoderate quantitative attack to work, though, “you request a definite magnitude of data,” Catling says. “And astatine nan moment, it’s benignant of spotty.”

Tedious though it whitethorn be, scientists must for now beryllium satisfied to proceed pinch “business arsenic usual” successful their hunt for life connected Mars. New devices specified arsenic AI-augmented robotic explorers and machine-learning algorithms that analyse observations whitethorn travel to nan fore, but nan halfway objectives stay unchanged: Keep looking deeper for clues hidden successful nan Martian stone grounds and gradually build up a much complete knowing of nan planet.

In different words, nan frustrating but basal task is to someway toggle shape gobs of “ordinary” information into an relationship that mightiness show america thing “extraordinary” astir Mars and its history. That doesn’t rather recapitulate Sagan’s strict criteria—it’s much of a variety connected a theme—but it doesn’t profoundly deviate from them, either.

“I deliberation we beryllium it to nan organization and to ourselves—to humanity, really: if you’re going to make a declare for illustration this,” Williams says, “you person to beryllium right.”

The hunt for life connected Mars is filled pinch cautionary tales of scientists who made awesome claims and past had to locomotion them back. But according to Benner—a somewhat iconoclastic intelligence who is self-employed via his nonprofit investigation organization, nan Foundation for Applied Molecular Evolution—this troubled bequest has near today’s astrobiologists excessively cautious and incapable to spot what, to him, is progressively obvious.

“More apt than not,” location is life connected Mars today, he argues. And nan Viking landers astir apt detected it a half-century ago. The subject community’s corporate nonaccomplishment to admit this, he says, “is an fantabulous illustration of really subject is not self-correcting, moreover erstwhile nan facts are clear.” (Benner’s peers find his views connected Viking controversial, to opportunity nan least.)

Each Viking lander carried 3 biology experiments, each designed to observe nan metabolic murmurs of microbes that mightiness unrecorded successful nan planet’s dirt. One research added h2o and nutrient soup to nan ungraded and looked for respired gases. Another added nutrient broth with a radioactive tracer to ungraded and past looked to spot whether immoderate of those “radiolabeled” traces emerged successful exhaled c dioxide. The 3rd asked whether a process for illustration photosynthesis could incorporated radiolabeled c dioxide into integrated molecules.

Curiously, astatine some landing sites, nan Martian ungraded that was exposed to radiolabeled broth seemed to nutrient radiolabeled gases. “The curve was incredible,” Young recalls. “If you looked astatine conscionable that experiment, it could not person been much positive.”

Yet nan ngo squad yet declared present-day Mars a lifeless world. Another instrumentality onboard, a wide spectrometer designed to observe integrated molecules, had seemingly travel up empty. And that was a conundrum because nary 1 could explicate really life mightiness beryllium wherever integrated molecules do not.

“That influenced everybody, myself included, into reasoning ‘life’ is retired of nan question,” McKay says. “You can’t person life without organics.” No organics, nary life:for a time, that disappointing conclusion formed nan ngo arsenic a nonaccomplishment and slammed nan brakes connected NASA’s Mars exploration program.

“The point that we really learned from Viking was that biology discourse is highly important,” McCauley Rench says. “You can’t conscionable ‘go effort to observe life.’ This is portion of what makes nan hunt truthful hard.”

It would return 20 years and different tantalizing hint of life connected Mars to revive nan abstraction agency’s liking successful nan planet. In 1996 scientists recovered what looked for illustration mini microbial fossils embedded successful a Martian meteorite that had been collected from Antarctica’s Allan Hills region. Years later nan “discovery” was yet deemed a misinterpretation but not earlier it inspired past president Bill Clinton to picture it successful a televised address arsenic a “vindication of America’s abstraction program.”

This particle microscope image of nan Martian meteorite Allan Hills 84001 shows linear, tubelike structures resembling microbes.

NASA

NASA’s renewed Mars programme would prosecute a much modest, incremental goal: to understand whether nan satellite was erstwhile habitable alternatively than whether thing still lived location aliases ever had. But a partial solution to Viking’s Mars life conundrum turned up unexpectedly successful 2008. In nan ungraded astatine its perch successful nan Martian arctic, NASA’s Phoenix lander recovered perchlorate salts—which thin to destruct integrated molecules upon heating.

If perchlorate was communal successful Martian soils, McKay and others argued, that would explicate why Viking’s wide spectrometer hadn’t seen organics: nan perchlorate had chewed done them during nan experiment. And it is so very communal connected nan planet: successful 2013 Curiosity besides recovered perchlorate successful Gale Crater, 3,500 miles distant from nan Phoenix lander.

“That’s erstwhile nan communicative changed dramatically,” McKay says. “‘No organics’ goes retired nan window. There were organics there, and location was perchlorate there.”

Curiosity and Perseverance each followed up by definitively detecting integrated compounds astatine their respective landing sites successful a bid of discoveries that continually revealed more analyzable molecules. Mars was proving to beryllium richer and much chemically move than astir scientists had dared to dream—even though some, including nan precocious Gil Levin, main interrogator for Viking’s branded merchandise experiment, had suspected arsenic much. “To nan time Gil died,” Young says, “he was convinced that life was there.”

NASA’s Viking 1 lander snapped this image of a Martian sunset from nan planet’s Chryse Planitia region connected Aug. 21, 1976.

NASA/JPL

In truth, scientists don’t request “life” to explicate Levin’s branded merchandise results. That research sampled a process called oxidation, successful which larger molecules are surgery down and stripped of electrons for energy. The Martian aboveground itself is people oxidizing: radiation breaks perchlorate into highly reactive compounds that don’t request power to degrade molecules. That could explicate really nan added nutrients were surgery down to merchandise radiolabeled c dioxide. Additionally, immoderate of nan nutrients successful nan broth could decay into c dioxide connected their own.

More caller activity by Benner and his colleagues revisits nan 3rd experiment—in McKay’s view, nan “orphan of nan Viking trio.” This often overlooked effort to spot if thing for illustration photosynthesis occurred successful Martian soils “absolutely gave what, prelaunch, was considered a affirmative result,” House says. But this Viking consequence made nary consciousness connected a satellite that was past thought to beryllium organics-free, and it was disavowed arsenic a mendacious affirmative by nan very scientists down it. Called nan pyrolytic merchandise experiment, nan investigation tested whether branded c atoms, successful c dioxide aliases c monoxide gases, were incorporated into larger integrated molecules. On Earth, photosynthetic organisms do this done a process called c fixation.

In a published paper and a caller book, Benner argues that this Viking research showed that something successful nan Martian ungraded appeared to beryllium turning inorganic state into integrated matter. That’s nan other of destroying organics, Benner says, and cannot beryllium explained by perchlorate aliases immoderate different oxidant. “There’s thing retired location correct now which explains that result,” he says.

That is, location is thing except, perhaps, life.

Benner makes an important statement that is not easy to dismiss, McKay says, arsenic agelong arsenic his assumptions are right. “Evidence of simplification connected specified an oxidizing world would beryllium difficult to understand without invoking life,” McKay says. But some McKay and Benner admit that much activity is needed to genuinely rewrite our knowing of Viking’s oft-overlooked experiment.

For now, Viking’s results whitethorn proceed to remainder successful ambiguity—at slightest until scientists return to Mars pinch a fresher suite of life-detecting instruments and a batch much accusation astir our vermillion neighbor’s surface. No much getting fooled by perchlorate aliases premature declarations of sterility—just an acknowledgment that erstwhile we situation to inquire large questions, we whitethorn not instantly understand nature’s answer.

“I do sometimes deliberation astir nan Viking experiments and really absorbing it would beryllium if, 100 years from now, we admit that that was nan first clip life was recovered connected Mars,” Grinspoon says, “and we conscionable didn’t judge it for different 75 years.”