This news was anticipated by an article in The Guardian as the speculation was building up, "Whatever the Curiosity rover has found, it's not evidence of life on Mars."
The author's evidence for that bold headline claim was earlier reporting on the issue as the speculation built up.
"Whatever Curiosity has found, it is not evidence for life on Mars. It can't be. Curiosity is not designed to look for life. Grotzinger has stated this himself. In a Nasa video about the mission, he says, 'Curiosity is not a life detection mission. We're not actually looking for life; we don't have the ability to detect life if it was there.'
"Following up the internet speculation, Jeffrey Kluger of Time talked to Nasa's Jet Propulsion Laboratory spokesperson Guy Webster and was told, 'It won't be earthshaking, but it will be interesting.'"
Organic molecules (molecules containing carbon) are commonplace in many lifeless places around the Solar system, so this is hardly surprising. It is moderately interesting, but certainly not earthshaking, as previously reported.
AFTER EDIT: Replying to the first reply kindly posted to my comment,
I'm not arguing whether Curiosity has found evidence for life on Mars or not but I would like to point out a logical fallacy in the cited argument; in particular, the statement "device X wasn't designed to do Y" does not imply "device X can't do Y".
I take the statement made by the NASA planners at face value for a simple reason. While the Curiosity rover, with its cameras, would surely be able to detect Martian megafauna, if there were such a thing, for example a Martian elephant, I trust the statement that Curiosity is incapable of providing unambiguous evidence of microorganisms on Mars. I cited the Guardian article in my first posting of this comment. The issue of detecting life, or not, was surely discussed by the NASA mission planners, who included astute exobiologists. The mission profile of Curiosity does not include a task of detecting life on Mars, and the instruments on Curiosity are not reliable for distinguishing organic molecules made by living microorganisms from organic molecules made by purely physical processes. Whatever Curiosity detects with its molecular analysis instruments, it cannot be taken as evidence for life on Mars. That is the statement of the article, based on interviews with people knowledgeable about the planning of the mission, and that is a credible statement, given the amount of thought the mission planners must have devoted to this issue.
They detected organic molecules on Mars decades ago, and we are now seeing proof that those who refused to accept the evidence were wrong. I wish I recalled the name of the scientist that designed the test done in the late 80s. He was far more polite and gracious than he should have been. He detected signs that were EXACTLY what they went in looking for in the first place, no one else even proposed an alternative explanation, they just decided to ignore it with pigheaded stubbornness. I hope news agencies dig up the man (I believe he is still alive, he is mentioned in the fairly recent book '13 Things That Don't Make Sense') and they have some of his contemporaries apologizing for going with their hearts instead of their brains.
I'm not arguing whether Curiosity has found evidence for life on Mars or not but I would like to point out a logical fallacy in the cited argument; in particular, the statement "device X wasn't designed to do Y" does not imply "device X can't do Y".
I think what he(?) was pointing out simply that the lack of design intention doesn't mean lack of functional capability. Certainly my fingers weren't designed to type, yet there it goes. The other side of such a fallacy would be akin to stating that because I can type with my fingers, they must have been "designed" (intelligently?) to type. So abstractly, I have to agree (since it was posed in an abstract variable replaceable way).
In this case, however, since the scientists know what they'd need to "prove" life, they can state that Curiosity doesn't have enough sensor capability to gather such evidence. Rather than stating that Curiosity was not designed to detect life, it would be more appropriate to state that Curiosity is incapable of providing rigorous proof of life.
Now, back to the evidence. Stating that what Curiosity has found is not evidence, may be taken at face value only if we narrow the definition of "whatever Curiosity has found" to the information capable of being gathered and returned, as opposed to the sources of the exhibits under observation (which may or may not have a biological origin, or may or may not be a precursor to biologic functions). A thin metaphysical/epistemological distinction to be sure, but one that is relevant because when we need to trust our senses, we need to know our sensor limits, and when we need to trust remote sensors, extra-terrestrial remoteness is as remote as it gets, and its hard limits cannot be easily overcome once deployed.
Curiosity is loaded with sensors, these can be used to draw conclusions they weren't designed for. Here's an admittedly absurd example: if Curiosity's cameras recorded a Martian puppy running around it, scientists would almost certainly consider that conclusive evidence for life.
It would be evidence but not conclusive evidence. In this case, we might think it was some sort of horrible prank played by a disgruntled scientist who hacked the instruments. But it might be enough for a second mission designed to conclusively verify the existence of life.
What if the Martian puppy started licking Curiosity and started to reprogram the cameras and antennas to communicate with us like an interplanetary telephone system?
That would be a pretty conclusive proof of live even though Curiosity wasn't designed to work in that way.
The ability of a device to detect "life" depends on the assumptions about what types of life one expects to find and what level of certainty is required.
Curiosity could certainly detect certain kinds of life... but not the types of life astrobiologists are guessing might exist near the surface. Curiosity definitely can detect active chemical processes for which there would be few if any non-biological explanations... but after so many false positives in the past the science community has decided that alone would not be definitive proof.
Curiosity was not built to detect life, but it can. However scientific conservatism would likely mean any “yes” result would be interpreted as a ”maybe.”
http://www.guardian.co.uk/science/across-the-universe/2012/n...
The author's evidence for that bold headline claim was earlier reporting on the issue as the speculation built up.
"Whatever Curiosity has found, it is not evidence for life on Mars. It can't be. Curiosity is not designed to look for life. Grotzinger has stated this himself. In a Nasa video about the mission, he says, 'Curiosity is not a life detection mission. We're not actually looking for life; we don't have the ability to detect life if it was there.'
"Following up the internet speculation, Jeffrey Kluger of Time talked to Nasa's Jet Propulsion Laboratory spokesperson Guy Webster and was told, 'It won't be earthshaking, but it will be interesting.'"
Organic molecules (molecules containing carbon) are commonplace in many lifeless places around the Solar system, so this is hardly surprising. It is moderately interesting, but certainly not earthshaking, as previously reported.
AFTER EDIT: Replying to the first reply kindly posted to my comment,
I'm not arguing whether Curiosity has found evidence for life on Mars or not but I would like to point out a logical fallacy in the cited argument; in particular, the statement "device X wasn't designed to do Y" does not imply "device X can't do Y".
I take the statement made by the NASA planners at face value for a simple reason. While the Curiosity rover, with its cameras, would surely be able to detect Martian megafauna, if there were such a thing, for example a Martian elephant, I trust the statement that Curiosity is incapable of providing unambiguous evidence of microorganisms on Mars. I cited the Guardian article in my first posting of this comment. The issue of detecting life, or not, was surely discussed by the NASA mission planners, who included astute exobiologists. The mission profile of Curiosity does not include a task of detecting life on Mars, and the instruments on Curiosity are not reliable for distinguishing organic molecules made by living microorganisms from organic molecules made by purely physical processes. Whatever Curiosity detects with its molecular analysis instruments, it cannot be taken as evidence for life on Mars. That is the statement of the article, based on interviews with people knowledgeable about the planning of the mission, and that is a credible statement, given the amount of thought the mission planners must have devoted to this issue.