DEAD OR ALIVE? No firm evidence exists that the Red Planet hosts life, but some researchers maintain that a living Mars remains a possibility.
Image: NASA
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Microbes similar to those on Earth would have a tough time surviving the harsh environment of Mars, but it is not inconceivable that they could persist there given a little protection, according to a new study. The finding supports similar, previous work and lends credence to the theory that if microbial life ever arose on Mars, it could exist below the planet's surface to this day.
Mars is in most respects a terrible habitat for life as we know it: winter temperatures can dip below –100 degrees Celsius, the atmosphere contains little oxygen, and without the benefit of a robust ozone layer the Martian surface is bombarded with ultraviolet (UV) solar radiation.
In a paper submitted to Planetary and Space Science that was posted to the online preprint repository arXiv.org on February 22, a group of Italian researchers presents the results of submitting a number of terrestrial bacteria to simulated Martian conditions. Giuseppe Galletta, an astronomer at the University of Padova in Italy, and his colleagues introduced bacterial species, including three strains from the Bacillus genus and a strain of Mycobacterium smegmatis, to their LISA and mini LISA experimental chambers.
The enclosures provide a rough facsimile of Mars's surface—they are cooled by liquid nitrogen to create extreme Martian cold, bathed in UV light, and flooded with a low-pressure carbon dioxide atmosphere. (Mini LISA, a series of small enclosures, was built to prolong the running time of the experiments on a single tank of coolant; the laboratory is housed in a medieval castle in Padua, a historic site that can only accept coolant deliveries once a week.) The researchers varied the environmental parameters to simulate the drastically different conditions found on Mars depending on the season and the time of day.
Galletta and his colleagues found that the bacteria handled the temperatures, low pressures and lack of oxygen relatively well but that the UV intensity all but wiped out the colonies in minutes. Even the extremophile Deinococcus radiodurans, which can endure mammoth blasts of gamma rays hundreds of times more powerful than would kill a human, could not last 10 minutes under UV exposure.
Similar experiments have been carried out in the past, including many that have sought to determine the threat of terrestrial microbes stowing away on Mars-bound spacecraft and contaminating the Red Planet. In those studies, UV irradiation was also shown to be a lethal force for bacteria, although the other atmospheric effects seemed to at least retard the growth of bacterial colonies.
The Italian group found that bacterial spores fared much better than active cells; the Bacillus spores survived for more than an hour, albeit in low numbers. (Perhaps counterintuitively, more spores actually endured during simulated Martian winter, at –80 degrees C, than during summer, at 23 degrees C.) The study's authors report that spores shielded from UV light, as might occur on Mars beneath the frozen surface or in a cave, stabilize in a dormant state before reactivating in the presence of liquid water. "This is important for Mars, because if underground water exists this may mean that life could survive in some ecologic niches," Galletta says.
Galletta notes a major caveat of such research—the presumption that Mars life, if it ever existed, bears any resemblance to Earth life. The theory of panspermia, or the early transport of life between the planets, would imply that to be the case if proved out. But if life arose independently on Mars it could take a form completely distinct from terrestrial organisms. "The limitation is that we only ever test on terrestrial life," Galletta says. "We don't know if our conclusions will be universal."
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19 Comments
Add CommentVery interesting. I wonder if much thought has been given to the possibility of chemotrophic organisms living interstitially at depth in the crust down to some depth where temps and conditions make it impossible, much as it is here on Earth. I've read something that claims something to the effect that if all the microbial life that exists deep within the fractured rock of the crust where temps and humitidy allow for life by chemotrophic life were scraped-off and put in one container its mass would excede the mass of all other life. Sounds extreme but it is singularly pervasive at depth where-ever humans have drilled looking for it, in conditions that one would not normally consider likely, if even possible. But there they are, and it's been suggested that the surfaces of minerals could have been the cradle in which the earliest combinations of chemicals resulted in self-reproducing compounds and which then moved away from the source, adapting as they went, once natural selection began to favor those that could live up in the harsher or more varied/better conditions within the panet's watery component or worse: the exposure to air and sunlight.
Reply | Report Abuse | Link to thisI for one would like to see some evidence of past life on Mars but rather think it will be found in its most enduring expression wherever chemicals, temp and water are present and acting on one another as nature suggests it must.
doug l - Well said. I agree especially that the requirement imposed to withstand UV was unnecessarily extreme, given that it can be so easily avoided by microbes. I'm not sure how much subsurface thermal relief is available on Mars, but surely there's enough variety of micro-environmental conditions there for microbial life to survive in some nook or cranny. Perhaps we just haven't looked in the right places yet.
Reply | Report Abuse | Link to thisLately, when I hear questioning discussion regarding the search for life on Mars, I find myself hoping we don't...at least not right on the surface. After reading Kim Stanley Robinson's remarkable novels about the terra-forming of Mars in the not-too -distant future, "Red Mars", "Green Mars" and "Blue Mars" I realize that finding life would mean that any terraforming would have to wait for a very long time as we examined the surface...maybe we could start terraforming Venus instead.
Reply | Report Abuse | Link to thisWhile many think that finding life on other planetary bodies (for all we know there is warm wet crustal material in other contexts besides our planet) would be a discovery of staggering proportions, I think that learning that we could go to another planetary body, or create a platform in deep space, and become a truly space-faring civilization would be even more of a milestone for our civilization. Tally ho!
Microbial life on Mars may have been already found?
Reply | Report Abuse | Link to thisMovement of Microorganism-like objects caught on the Mars Phoenix Microscopic imager by time-lapse imaging. Judge for yourself -- is this the first real Martian Life forms that the world will ever see?
http://www.youtube.com/watch?v=zhfSjJeQf58
I used to imagine the surface of Mars being barren, but the more stable areas being excavated and revealing fossils. ...with a few specimens frozen in ice.
Reply | Report Abuse | Link to thisIt's nice to imagine.
How can I understand this video on the youtube is trick?
Reply | Report Abuse | Link to thisHow can I understand this video on you tube is not trick?
Reply | Report Abuse | Link to thisIt's not a trick, go to the original website at NASA JPL here:
Reply | Report Abuse | Link to thishttp://www.nasa.gov/mission_pages/phoenix/images/index.html
and extract out the raw Images from the Optical Microscope, they are raw grayscale images in order to make a color image you need the RGB images, red, green, blue, take the images from the same sol listed on the YouTube time lapse movies and you can animate it yourself.
rlb2 – Cool – it’s not a fake. It could be life, but motion doesn’t necessarily indicate life and not all life produces motion. Other explanations for the motion indicated have not been ruled out. The youtube animation runs a few seconds producing a dramatic effect from apparent motion that occurred in a few frames shot over 15 min. All said though, it could be some form of microbial life!
Reply | Report Abuse | Link to thisIn the interest on accuracy and precision, I'd like to modify my statement from "Cool - it's not a fake" to "Cool - It does appear to be a valid transformation of genuine images from the Mars Phoenix Lander that indicates motion of some sampled objects, but I am not qualified and haven’t investigated it enough to fully authenticate it."
Reply | Report Abuse | Link to thisThanks jtdwyer there were some input from mhhecht on the Phoenix Lander science team in the comment section of the YouTube section that tries to explain it but I am not sure that is what she claims happened in a few of the sol's as listed below.
Reply | Report Abuse | Link to thismhhecht comment -
"Ron,
These substrates are vertical, and we moved them in and out between frames to adjust the focus. The stage vibrates when we do this, and some particles slide down. Most of your animations are of our magnetic substrates, and the sliding tells us which particles are more or less magnetic (the reddish glassy ones move more readily than the coarse brown ones). This helps us understand how the various types of particles formed.
By the way, I admire your initiative, and apologize for the slowness of the Phoenix project in posting our own color composites."
Keep in mind the Phoenix science team has confirmed that the Phoenix Lander was in a place on Mars that was nutrient rich with all the ingredients to sustain life as we know it today...
I have a lot of respect for mhhecht answer above and don't have the tools to collaborate the above statement, because that was one of my first concerns. I would need access to all the data pinpointing the times of sols they moved the substrates or turned the magnetic instrument on and off to agree or disagree with her statement, this is buried in the mass amount of data they received.
I did suspect that before I put together the final time lapse images and saw the matrix of some of the daily sol in question JPL put out and according to it the magnetic substrate instrument wasn't turned on during sol 70, maggot-like movement and sol 123 scorpion-like object movement, don't know how accurate that matrix was.
There is a lot of unanswered questions that's why in a tongue and cheek type way I called it a UMO, unidentified moving objects....
rlb2 - I should have explained that my comments were my own conclusions from examining the video and the discussion accompanying it - that no explanation for the apparent motion had been determined, and that the possibility that it represents microbial activity has not been definitively ruled out.
Reply | Report Abuse | Link to thisOnce the Spanish arrived in South America--they took the gold. Even though there was "life" already there.
Reply | Report Abuse | Link to thisSo, with the precedent set, if there is life on Mars we should immediately tax them of all their gold.
Of course, getting it home may cost more than its worth. But, since when has that ever stopped us? Iraq, anyone?
Interesting comments, thank you, and refreshing to see some properly scientific thinking and modesty amongst these comments.
Reply | Report Abuse | Link to thisI am more concerned that over 36 years of Martian landings by earth spacecraft may have released earth bacteria into the Martian environment. This earth bacteria, in the absence of competition or predators, may have gone underground on Mars and multiplied exponentially since the 1970s, accounting partially for the recent observations of methane outgassing from the Martian subsurface.
Reply | Report Abuse | Link to thisRick Dickson - Good point. That is a real concern, although NASA has has taken steps to avoid such an occurrence, it could only be ruled out by very close examination. With the levels of cosmic and Solar particles and extreme conditions encountered, even adapted Earth bacteria might be quickly unrecognizable, except perhaps through DNA analysis.
Reply | Report Abuse | Link to thiswhat if we are looking at Mars all wrong. what if instead of living on the outside it could be inhabitated on the inside maybe!
Reply | Report Abuse | Link to thisThough Mars atmosphere is uninhabiable for life as we know it on earth. But some extremophiles might survive there. Some of these organisms can live in extemely hot temperatues. Others live freezing below zero temperatures. There might be extremophiles like organisms living on Mars at this time.
Reply | Report Abuse | Link to thisThere are organisms on earth called extremophiles. Some of them live in scalding hot temperatures. and others live in freezing below zero temperatures. These organisms might survive the harsh martian atmosphere. Also there may be extremophile-like organism currently living on Mars.
Reply | Report Abuse | Link to this