\n<\/p>\n
Chalk up another victory for \u201cConan the Bacterium\u201d\u2014a rugged germ that fresh research suggests could conquer the solar system.<\/p>\n
Better known as Deinococcus radiodurans, this microbe is arguably the toughest organism known to science. Past studies have shown it can endure extreme cold, intense radiation, harsh chemicals and profound dehydration\u2014all evolutionary adaptations, perhaps, to what\u2019s thought to be its natural home in the high, dry and sun-scorched deserts of northern Chile.<\/p>\n
Now a new experiment from researchers at Johns Hopkins University shows this hardy \u201cextremophile\u201d can also survive the immense shocks and mechanical stresses associated with asteroid strikes on Mars.<\/p>\n
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D. radiodurans \u201cis the closest thing we can get to what we think a Martian life-form might look like without having an alien in our lab,\u201d says Lily Zhao, a doctoral student at Johns Hopkins University, who led the experiment. \u201cAnd we tried to kill it, but we couldn\u2019t.\u201d<\/p>\n
To do so, the researchers fired a high-speed projectile from a gas gun at colonies of D. radiodurans that were sandwiched between two steel plates. The bacteria could withstand split-second exposures to extreme pressures of up to three gigapascals (GPa). That\u2019s 30 times greater than pressures at the deepest point in Earth\u2019s oceans\u2014and similar to the crushing blow of an asteroid cratering into Mars and blasting fragments into space.<\/p>\n
K. T. Ramesh, an impact expert at Johns Hopkins, who supervised the work, was shocked by the results. \u201cOur expectation was that most of them would die,\u201d he says, because other types of microbes in previous high-pressure studies had survival rates of only about 1 percent or less. Instead nearly all the D. radiodurans microbes survived initial 1-Gpa shots. Even at the highest pressures of 3 Gpa, more than half survived. Subsequent analyses, guided by Johns Hopkins microbiologists Cesar A. Perez-Fernandez and Jocelyne DiRuggiero, showed that some of the microbes had perished from ruptured cell walls but also confirmed the survivors could repair their damaged DNA, regrow and reproduce.<\/p>\n
These images show Deinococcus radiodurans microbes before (left) and after (center, right) high-pressure impact experiments.<\/p>\n
Lisa Orye\/Johns Hopkins University\/Zhao et al.<\/p>\n
Along with the microbe\u2019s other feats of strength, its extraordinary resilience suggests it has all the basics required for interplanetary hops onboard an impact\u2019s ejected debris that could sow life throughout the solar system, the researchers say. Called lithopanspermia, this far-out idea dates to musings in the 1870s about germ-riddled meteorites. Scientists began taking it more seriously in the 20th century, however, as space exploration revealed potentially habitable conditions on other planets and as cellular biology showed some microbes to be astonishingly adaptive and robust.<\/p>\n
\u201cIn terms of fundamentals\u2014radiation, freezing, desiccation\u2014this \u2018pressure\u2019 component was really the last question mark,\u201d Zhao says, \u201cbecause, if life couldn\u2019t even survive impact pressures, then the rest doesn\u2019t matter since cells won\u2019t survive being launched into space in the first place.\u201d<\/p>\n
The team\u2019s results, published on Tuesday in the journal PNAS NEXUS, carry weighty implications for understanding the origins of life on Earth\u2014and the search for life elsewhere in the universe.<\/p>\n
The finding bolsters the case that life across a solar system may spread a bit like the common cold: if one bio-fevered planet sneezes out debris, others can catch it, too. And given that asteroids have been chipping away at the sun\u2019s retinue of worlds for more than 4.5 billion years\u2014and that, eons ago, Mars was a warmer, wetter, more clement place\u2014the result boosts the possibility, however slight, that life on Earth got its start on Mars. Meteorites from the Red Planet routinely pelt our planet, although most burn entirely in the atmosphere or fall into desolate stretches of land or sea.<\/p>\n
Scientists are not suggesting that homegrown D. radiodurans microbes are direct \u00e9migr\u00e9s from Mars. Rather this terrestrial organism\u2019s capabilities are a sort of existence proof. \u201cIf you can get one life-form, an extremophile, to survive these kinds of conditions, that shows there\u2019s a \u2018seed\u2019 for biology to build on,\u201d Ramesh says. \u201cYou\u2019ve got the DNA; you\u2019ve got the cellular structures. And from there, biology can move\u2014it doesn\u2019t start in one place and just stay there.\u201d Evolutionary adaptation handles the rest.<\/p>\n
\u201cThis is a fantastic experimental representation of how microorganisms could propagate between neighboring planets or beyond in the universe by hitching a ride in rocks that were ejected from an impact,\u201d says Moogega Cooper, a planetary protection engineer at NASA\u2019s Jet Propulsion Laboratory, who works on the space agency\u2019s Curiosity Mars rover and wasn\u2019t part of the latest study.<\/p>\n
Planetary protection engineers such as Cooper ensure Earth\u2019s life doesn\u2019t stow away on spacecraft to contaminate and gain a flagellum-hold on other worlds, where it could muddle the search for extraterrestrial life and potentially wreck alien ecosystems. They also safeguard our own planet from otherworldly life-forms brought back from space. \u201cFinding signs of life beyond our planet in a way that clearly differentiates it from Earth life must be done in a clean manner,\u201d Cooper says.<\/p>\n
The NASA-led Mars Sample Return (MSR) program\u2014a decades-in-the-making quest to bring potentially life-bearing Martian material back to Earth\u2014is now in shambles, its budget zeroed-out just as the space agency\u2019s Perseverance rover had gathered the requisite samples, leaving them stranded on the surface of Mars. But another effort is quietly waiting in the wings: the Japan Aerospace Exploration Agency\u2019s (JAXA\u2019s) Martian Moons Exploration (MMX) mission is set to launch later this year on a voyage to grab samples from Mars\u2019s moon Phobos for return to Earth in 2031. In light of the Johns Hopkins study, it\u2019s suddenly conceivable that MMX might deliver some of what MSR had promised.<\/p>\n
\u201cPhobos orbits Mars twice daily at an orbital distance of just 3,700 miles and has effectively been acting as a vacuum cleaner for ejecta from the Martian surface for the last billion years,\u201d says Michael Daly, a pathologist and extremophiles expert at Uniformed Services University of the Health Sciences in Maryland. \u201cThe Johns Hopkins group\u2019s research brings renewed focus to the possibility of detecting not only prebiotic small molecules but also macromolecular remnants of whole cells and viruses ejected from Mars\u2019s surface. Indeed, the remarkable ability [of D. radiodurans] to potentially survive both the immense pressures of meteorite impact and eons of deep-space radiation suggests that the MMX Phobos moon samples returned to Earth may require a higher level of planetary protection.\u201d<\/p>\n
Phobos has been considered uninhabitable and is therefore classified as an \u201cunrestricted\u201d celestial body by the United Nations\u2013affiliated Committee on Space Research (COSPAR), which dictates planetary protection protocols. That status means minimal biohazard measures are required for visiting spacecraft. Daly notes, however, that recent discoveries of sugars, amino acids and other biological building blocks on asteroids could allow impact-delivered organisms to be planted and fertilized in the Martian moon\u2019s soil, allowing long-term survival. That is, COSPAR may need to reconsider its designation\u2014with unclear repercussions for the soon-to-launch MMX mission.<\/p>\n
\u201cSo you go to Phobos, you bring material back, and maybe you bring back [biological] Martian material,\u201d Ramesh says. \u201cMaybe you have to be worried about this now, right? You may have to be more careful than we previously thought.\u201d<\/p>\n
Cooper, the NASA planetary protection expert, notes that the Martian moon\u2019s \u201cunrestricted\u201d status emerged in part from an authoritative 2019 report from the National Academies of Sciences, Engineering, and Medicine and that NASA has already funded an in-progress study to further assess impact-ejected microbial survival on Phobos. \u201cThe burden of proof will require more research,\u201d she says. \u201cBut future experiments could support a deeper conversation exploring unrestricted sample return from Mars in an updated safety assessment like the JAXA MMX mission.\u201d<\/p>\n
Norman Sleep, a Stanford University geophysicist and pioneer in modern lithopanspermia studies, thinks the MMX Phobos samples will justifiably receive extremely careful treatment regardless of the moon\u2019s planetary-protection status. \u201cSome people\u2014I won\u2019t say who\u2014think that demanding planetary protection for bringing samples back from Phobos is like requiring a lifeguard for a swimming test at Death Valley National Park,\u201d he quips. \u201cBut even so, it\u2019s worth taking Herculean efforts to keep the Phobos samples from being contaminated by terrestrial microbes.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"
Chalk up another victory for \u201cConan the Bacterium\u201d\u2014a rugged germ that fresh research suggests could conquer the solar system. Better known as Deinococcus radiodurans, this microbe is arguably the toughest organism known to science. Past studies have shown it can endure extreme cold, intense radiation, harsh chemicals and profound dehydration\u2014all evolutionary adaptations, perhaps, to what\u2019s<\/p>\n","protected":false},"author":1,"featured_media":45952,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50],"tags":[1871,1874,589,265,337,369,3394,22462,188,3415],"class_list":{"0":"post-45951","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-environment","8":"tag-asteroid","9":"tag-debris","10":"tag-earth","11":"tag-impact","12":"tag-life","13":"tag-mars","14":"tag-reach","15":"tag-riding","16":"tag-study","17":"tag-suggests"},"_links":{"self":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/45951","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=45951"}],"version-history":[{"count":0,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/posts\/45951\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=\/wp\/v2\/media\/45952"}],"wp:attachment":[{"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=45951"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=45951"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/naijaglobalnews.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=45951"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}