Probably not. But it certainly has lifeforms on it that are still viable, because it wasn't 100% sterilized. That's very hard, almost impossible with modern technology because though you can sterilize things 100%, it usually involves temperatures and other conditions that are extreme enough to damage modern scientific equipment. Instead they use methods that remove "nearly all" the microbes.
Indeed for Curiosity the aim was a maximum of 300,000 dormant microbes over the entire spacecraft on launch (not including internal electronics which are protected from the exterior by a microbe barrier). That's cultivable spores. There could be as many as a hundred times as many non cultivable dormant spores. But those numbers would be reduced a fair bit during the long flight there and the landing and then on the surface of Mars through UV, cosmic radiation and vacuum conditions, for that matter the chemicals in the dust. Also they managed a bit better than the objective so probably less than 300,000 originally.
But though Mars is very hostile for most forms of life, almost certainly some still survive at least in dormant states. (With the populations continually reduced further by the harsh conditions there, but there may still be a few that are viable to this day).
As for types of life, tests of spaceship assembly clean rooms show that they have a wide range of microbes including extremophiles, indeed the conditions rather favour extremophile lifeforms.
If there were any habitats on Mars for them, then they would have a chance of contaminating Mars. But they think that there are no habitats in the equatorial regions where it is. There's some evidence that there might be "warm seasonal flows" close enough for it to visit them. If that is true, then it is not sufficiently well sterilized to go right up close to them.
I think though it's important to know that none of this is tested with any measurements on Mars to test to see how well our planetary protection measures are working. We haven't sent any mission to look at our Mars rovers and their vicinity to see if there is any life there. It's more like a prediction, that they think they are suffiicently clean so that mars is not contaminated.
I actually think this should be a priority - to send missions to look at our previous landers on the ground to see if there are microbes left on them or whether they have spread, at all, to the land around them. One way to do that might be to send a life mission to search for present day life - maybe also past life - and then at the same time to try searching for life on a previous rover sent to Mars earlier as part of the mission, and in the ground around it.
Hopefully that would show no contamination around the rover - though we'd expect to find some viable microbes on the rovers themselves, just dormant doing nothing.
And then we could have complete confidence, or reasonably so, that our planetary protection measures are working in the equatorial regions. And once we can sterilize sufficiently, do the same in the polar regions e.g. around the Phoenix landing site. And if we do find that some life has started to spread, say from the vicinity of Phoenix or whatever, maybe we can reverse it, if we catch it early enough, given that life would grow very slowly in such conditions. In any case whatever has happened or, hopefully, not, is good to find out so we can decide how to continue based on good information about the situation now.
Once again, scientists when they discuss this generally say that though we have undoubtedly brought dormant life to Mars on our rovers, the chances are high that it is still in dormant state, just sitting there doing nothing because the surface is so hostile.
One exception here though is Gilbert Levin. He thinks that Viking discovered life already in the 1970s. He thinks that there may be habitats for life even in the equatorial regions, perhaps using the frosts that form every morning, in some way, to get water. Or just the humidity of the air. If he is right, there is a higher risk that contamination from our rovers could have introduced Earth life to Mars. Or indeed if there are any other undiscovered present day habitats in the equatorial regions, for instance the recently discovered thin water layer below the level of the surface in sand dunes (indirect detection through humidity measurements), thought to be too salty in daytime and too cold at night for life. But what if,through some fluke, there are occasional micro-habitats for life there. One exobiologist, Nilton Renno, speculated about this, observing that microbes are often able to control their own micro-environment, so what if they are able somehow to make the conditions just a bit more humid in daytime than you'd expect from the underlying chemistry of the situation?
I think we very much need good direct evidence on the ground about possible habitats, from rovers able to drill, and with life detection capabilities, before we know for sure what exactly is the risk whether we have contaminated Mars with Earth life.
Meanwhile scientists act on the assumption, probably justified, that there are no habitats for life in the equatorial regions except for the warm seasonal flows already discovered, and that this 300,000 spores on launch requirement is sufficient planet protection for Mars. They may very well be right.
See also Did we contaminate Mars with life?
For the Viking measurements, see Rhythms From Martian Sands - What Did Our Viking Landers Find in 1976? Astonishingly, We Don't Know
Indeed for Curiosity the aim was a maximum of 300,000 dormant microbes over the entire spacecraft on launch (not including internal electronics which are protected from the exterior by a microbe barrier). That's cultivable spores. There could be as many as a hundred times as many non cultivable dormant spores. But those numbers would be reduced a fair bit during the long flight there and the landing and then on the surface of Mars through UV, cosmic radiation and vacuum conditions, for that matter the chemicals in the dust. Also they managed a bit better than the objective so probably less than 300,000 originally.
But though Mars is very hostile for most forms of life, almost certainly some still survive at least in dormant states. (With the populations continually reduced further by the harsh conditions there, but there may still be a few that are viable to this day).
As for types of life, tests of spaceship assembly clean rooms show that they have a wide range of microbes including extremophiles, indeed the conditions rather favour extremophile lifeforms.
If there were any habitats on Mars for them, then they would have a chance of contaminating Mars. But they think that there are no habitats in the equatorial regions where it is. There's some evidence that there might be "warm seasonal flows" close enough for it to visit them. If that is true, then it is not sufficiently well sterilized to go right up close to them.
I think though it's important to know that none of this is tested with any measurements on Mars to test to see how well our planetary protection measures are working. We haven't sent any mission to look at our Mars rovers and their vicinity to see if there is any life there. It's more like a prediction, that they think they are suffiicently clean so that mars is not contaminated.
I actually think this should be a priority - to send missions to look at our previous landers on the ground to see if there are microbes left on them or whether they have spread, at all, to the land around them. One way to do that might be to send a life mission to search for present day life - maybe also past life - and then at the same time to try searching for life on a previous rover sent to Mars earlier as part of the mission, and in the ground around it.
Hopefully that would show no contamination around the rover - though we'd expect to find some viable microbes on the rovers themselves, just dormant doing nothing.
And then we could have complete confidence, or reasonably so, that our planetary protection measures are working in the equatorial regions. And once we can sterilize sufficiently, do the same in the polar regions e.g. around the Phoenix landing site. And if we do find that some life has started to spread, say from the vicinity of Phoenix or whatever, maybe we can reverse it, if we catch it early enough, given that life would grow very slowly in such conditions. In any case whatever has happened or, hopefully, not, is good to find out so we can decide how to continue based on good information about the situation now.
Once again, scientists when they discuss this generally say that though we have undoubtedly brought dormant life to Mars on our rovers, the chances are high that it is still in dormant state, just sitting there doing nothing because the surface is so hostile.
One exception here though is Gilbert Levin. He thinks that Viking discovered life already in the 1970s. He thinks that there may be habitats for life even in the equatorial regions, perhaps using the frosts that form every morning, in some way, to get water. Or just the humidity of the air. If he is right, there is a higher risk that contamination from our rovers could have introduced Earth life to Mars. Or indeed if there are any other undiscovered present day habitats in the equatorial regions, for instance the recently discovered thin water layer below the level of the surface in sand dunes (indirect detection through humidity measurements), thought to be too salty in daytime and too cold at night for life. But what if,through some fluke, there are occasional micro-habitats for life there. One exobiologist, Nilton Renno, speculated about this, observing that microbes are often able to control their own micro-environment, so what if they are able somehow to make the conditions just a bit more humid in daytime than you'd expect from the underlying chemistry of the situation?
I think we very much need good direct evidence on the ground about possible habitats, from rovers able to drill, and with life detection capabilities, before we know for sure what exactly is the risk whether we have contaminated Mars with Earth life.
Meanwhile scientists act on the assumption, probably justified, that there are no habitats for life in the equatorial regions except for the warm seasonal flows already discovered, and that this 300,000 spores on launch requirement is sufficient planet protection for Mars. They may very well be right.
See also Did we contaminate Mars with life?
For the Viking measurements, see Rhythms From Martian Sands - What Did Our Viking Landers Find in 1976? Astonishingly, We Don't Know
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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