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Waspie_Dwarf

False-positive signs of life on exoplanets

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Research trio suggests exomoon atmospheres could cause false-positive signs of life on exoplanets

(Phys.org) —A trio of space scientists has published a paper in Proceedings of the National Academy of Sciences in which they suggest that current assumptions regarding using spectral signatures as a means to identify exoplanets that may harbor life, has a major flaw—a false positive could occur if the planet has a moon with an atmosphere that contaminates the spectrum. In their paper, Hanno Rein, Yuka Fujii and David Spiegel of the University of Toronto, the Tokyo Institute of Technology and MIT respectively, point out a major problem with using spectral signatures as a means for finding out if life exists on other planets—moons which can cause the false impression of chemical disequilibrium.

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It would be interesting to have a planet evolve life at the same time as its moon.

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if we found life outside of earth in our own solar system first,at least we would know for sure.then i would imagine it would be easier get the funding that is needed for more ambitious projects

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if we found life outside of earth in our own solar system first,at least we would know for sure.then i would imagine it would be easier get the funding that is needed for more ambitious projects

It might be easier and cheaper to accept that there is other life in the universe so we can move on.

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It might be easier and cheaper to accept that there is other life in the universe so we can move on.

Yes because the way humanity has made scientific progress is just to make an arbitrary decision on what the truth is and then make no effort to find evidence to back up this decision.

Oh sorry, my mistake, that is the EXACT opposite of how humanity has made scientific progress.

Whether we are alone in the universe is one of the most important and fundamental questions facing science today. Guessing the answer is not a logical or sane way to answer that question.

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Yes because the way humanity has made scientific progress is just to make an arbitrary decision on what the truth is and then make no effort to find evidence to back up this decision.

Oh sorry, my mistake, that is the EXACT opposite of how humanity has made scientific progress.

Whether we are alone in the universe is one of the most important and fundamental questions facing science today. Guessing the answer is not a logical or sane way to answer that question.

It appears scientific logic already calculates that we are not alone in the universe. Other wise any attempt to find it is an illogical waste of time and money.

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Unless you are talking about an intelligent alien civilization that is emitting readable bands of energy in a form that we might recognize, i.e. radio waves, then it will be next to impossible to determine if life exists on an exoplanet. And it would be the greatest stroke of luck if we even happen to be listening in that direction when they are broadcasting.

Suppose you have a world with the equivalent of (only) plants and insects that inhale and exhale the same gases as our life does. Could you tell from Earth that these gases are not coming from non-organic geological processes? The sad thing is that, barring some practical space warping technology, it is completely impossible to send a probe to these worlds in any appreciable amount of time and have it return any data.

If we really hope to find alien life, I believe the best bet is still the ice moons of our own solar system's outer planets and even then it may only be microbial, if it exists at all.

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It appears scientific logic already calculates that we are not alone in the universe.

No it doesn't.

You can not mathematically extrapolate from a single result. Since Earth is the only known planet with life it is impossible to calculate how common life is.

Whilst most scientists believe life is common this is an assumption and is far from being a unanimous opinion.

Other wise any attempt to find it is an illogical waste of time and money.

The law of averages says that one of your opinions, one day will be correct. this, sadly, isn't it.

The very fact that we don't no whether life exists elsewhere in the universe means that searching for it IS a worthwhile and logical pursuit.

You have repeatedly demonstrated that you don't know how science works, now you are proving that you don't even know what science is.

Science (from Latin scientia, meaning "knowledge") is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.

Source: wikipedia

To be honest, based on past dealings with you, I don't expect you to understand that, so I'll give you a simpler explanation. Science does not accept assumptions or opinions even from experts in the field. For something to be accepted as fact (what scientists call a theory) it must be supported by observation or experimental proof.

The assumption that life exists elsewhere in the universe will remain an unproven hypothesis UNTIL life is observed elsewhere in the universe.

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Posted (edited)

Unless you are talking about an intelligent alien civilization that is emitting readable bands of energy in a form that we might recognize, i.e. radio waves, then it will be next to impossible to determine if life exists on an exoplanet.

Untrue and rather missing the point of the original article all together.

Life, even microbial life, alters the atmosphere of the planet (the oxygen in OUR atmosphere is the result of life).

With powerful enough telescopes it will be possible to take spectra of exoplanet atmospheres and determine their composition. From these results it may be possible to detect life many light years away.

Edited by Waspie_Dwarf

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Posted (edited)

No it doesn't.

You can not mathematically extrapolate from a single result. Since Earth is the only known planet with life it is impossible to calculate how common life is.

Whilst most scientists believe life is common this is an assumption and is far from being a unanimous opinion.

I see. My bad.

The law of averages says that one of your opinions, one day will be correct. this, sadly, isn't it.

The very fact that we don't no whether life exists elsewhere in the universe means that searching for it IS a worthwhile and logical pursuit.

How can you be so sure its worthwhile? Why does it mean so much to you?

You have repeatedly demonstrated that you don't know how science works, now you are proving that you don't even know what science is.

Source: wikipedia

To be honest, based on past dealings with you, I don't expect you to understand that, so I'll give you a simpler explanation. Science does not accept assumptions or opinions even from experts in the field. For something to be accepted as fact (what scientists call a theory) it must be supported by observation or experimental proof.

The assumption that life exists elsewhere in the universe will remain an unproven hypothesis UNTIL life is observed elsewhere in the universe.

The assumption that life DOESNT exist elsewhere in the universe could be just as valid a belief dont you think?

Edited by taniwha

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How can you be so sure its worthwhile? Why does it mean so much to you?

The real question here is why is scientific progress so meaningless to you?

Why do you not value a better understanding of the universe?

Why do you think ignorance is better than knowledge?

Why would you rather guess than know?

The assumption that life DOESNT exist elsewhere in the universe could be just as valid a belief dont you think?

Read the follow VERY slowly, I have said this to you over and over again, One day it might sink in:-

In science assumptions count for NOTHING, evidence counts for EVERYTHING.

Since assumptions count for nothing all assumptions are equally INVALID if they have no supporting evidence.

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...Since assumptions count for nothing all assumptions are equally INVALID if they have no supporting evidence.

Exactly.

What makes me lean towards there most likely being life elsewhere in the universe (verses there being no other life except here on Earth) is as follows:

1) The basic building blocks for life (amino acids) have indeed been found elsewhere.

2) Conditions on Earth do not appear to be all that extraordinary, other planets are being routinely discovered.

3) The universe is big...very, very big. The odds that there's someplace else with proper conditions for life is pretty good.

That all said, until we find other life we simply don't know for sure.

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I fully expect that there are life forms a lot of places, maybe even several in the solar system. That is a worry to me because such planets, each with its own chemistry. may hence be poisoned to possible human settlement.

What I don't expect is that there will be many advanced star-faring civilizations, for reasons I have posted many times.

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Exactly.

What makes me lean towards there most likely being life elsewhere in the universe (verses there being no other life except here on Earth) is as follows:

1) The basic building blocks for life (amino acids) have indeed been found elsewhere.

2) Conditions on Earth do not appear to be all that extraordinary, other planets are being routinely discovered.

3) The universe is big...very, very big. The odds that there's someplace else with proper conditions for life is pretty good.

That all said, until we find other life we simply don't know for sure.

I fully expect that there are life forms a lot of places, maybe even several in the solar system. That is a worry to me because such planets, each with its own chemistry. may hence be poisoned to possible human settlement.

What I don't expect is that there will be many advanced star-faring civilizations, for reasons I have posted many times.

Equally valid opinions but, of course, the "Rare Earth" hypothesis is also equally valid at the moment.

This contends that for multicellular life to take hold not only do you need a planet in the habitable zone, you also need the following:

  • The correct kind of galaxy. Some galaxies have far greater levels of x-ray and gamma-ray radiation than ours, greater rates of supernovae are also problematic.
  • The correct location within the galaxy. Radiation levels rise and the amount of metals decrease as you approach the centre. Stars are packed closer together and so near-by supernovae and perturbations of planetary and asteroid orbits by passing stars are more common.
  • The right kind of star, so that the planet is not bathed in harmful radiation, the habitable zone is not prohibitively small causing the planet to become tidally locked, the star's output is stable for extremely long periods of time and the star must have formed from a nebula containing enough metals for complex chemistry.
  • The planet must have a continuously stable orbit.
  • The planet must have large moon to produce tidal pools and stabilise the axial tilt of the planet.
  • The planet must be in a solar system that has gas giant in roughly the same position as Jupiter to protect the terrestrial planet from excessive cometary impacts.
  • The planet must be of the right size.
  • The planet must have plate tectonics.

It is possible to make a good case for life being extremely common. It is also possible to make a case for life being extremely rare. If we don't look we will never know which is correct.

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Indeed, the 'rare Earth hypothesis' has a great deal of evidence in its favour as well.

It could also be that there is other life, but do to its rare occurance, it's in another galaxy far, far away from us. So incredibly far as to essentially render us 'alone' for all intensive purposes!

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It could also be that there is other life, but do to its rare occurance, it's in another galaxy far, far away from us. So incredibly far as to essentially render us 'alone' for all intensive purposes!

Exactly. As the old saying goes,"absence of evidence is not evidence of absence."

Finding extraterrestrial life will prove that it exists. Not finding extraterrestrial life will NOT prove that it doesn't.

It is virtually impossible to prove the non-existence of something, this is why logic and science demand that the burden of proof is on proving a hypothesis, not on disproving it. A hypothesis can not be logically accepted (however much sense the proposer thinks it makes) if it is not supported by evidence.

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It is virtually impossible to prove the non-existence of something, this is why logic and science demand that the burden of proof is on proving a hypothesis, not on disproving it. A hypothesis can not be logically accepted (however much sense the proposer thinks it makes) if it is not supported by evidence.

If just this aspect of logic were to be understood and accepted discussion would be far more productive.

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I might modify your principle a little to say that while absence of evidence is not proof of absence, depending on the circumstances it can be pretty good evidence of absence. In the case of extraterrestrial life we haven't enough of a sample to draw conclusions, but often the assertion of the existence of a phenomenon can be pretty much dismissed when people check thousands of samples and don't find it.

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Posted (edited)

.... In the case of extraterrestrial life we haven't enough of a sample to draw conclusions, but often the assertion of the existence of a phenomenon can be pretty much dismissed when people check thousands of samples and don't find it.

If in the future if we send probes to large numbers of other planets and no sign of life is ever found, then the probability of life elsewhere would be considered as being quite remote. However, we have not done this as of yet. The only other planet we've managed to 'scope out' is Mars. A sample of "one" tells us nothing.

Edited by Lilly
typo
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The real question here is why is scientific progress so meaningless to you?

Why do you not value a better understanding of the universe?

Why do you think ignorance is better than knowledge?

Why would you rather guess than know?

Read the follow VERY slowly, I have said this to you over and over again, One day it might sink in:-

In science assumptions count for NOTHING, evidence counts for EVERYTHING.

Since assumptions count for nothing all assumptions are equally INVALID if they have no supporting evidence.

Scientific progress will never be able to prove that we ARE alone in the universe I will guarantee you that for free. Thats why the scientific drive is being funded to find it, unless they are spending all that money on mars trying to prove life doesnt exist? Does it seem logical to try and detect UNLIFE before sending humans? Yes. The moon was found to be lifeless before we landed. The trend will continue until life is found then a high authority will be enforced on Earth. A rule to rule all others. But thats the future so when you eliminate the impossible whatever is left is certainly possible.

For the present only Earth is known to have Life consisting of a solid liquid and a gas. Life here is an abundant truth so it is a just cause to look after our planet and its people firstly.

It is a sign of intelligence to ask the question, " is there life out there? "

The most intelligent answer has always been yes.

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I think the search for life on Mars is secondary and not really expected to find anything but worth it just in case. The real reason for all the study of Mars is to understand planets better, including our own.

We may never find ET out there, which would probably be a loss to us in overcoming our species chauvinism and in learning who knows what. If we do it will be a shock, especially to religions based on the idea that man is the center of God's plan. It won't help other religions much either (I don't expect to see them in saffron robes any more than Praising Allah).

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Scientific progress will never be able to prove that we ARE alone in the universe I will guarantee you that for free. Thats why the scientific drive is being funded to find it, unless they are spending all that money on mars trying to prove life doesnt exist? Does it seem logical to try and detect UNLIFE before sending humans? Yes. The moon was found to be lifeless before we landed. The trend will continue until life is found then a high authority will be enforced on Earth. A rule to rule all others. But thats the future so when you eliminate the impossible whatever is left is certainly possible.

For the present only Earth is known to have Life consisting of a solid liquid and a gas. Life here is an abundant truth so it is a just cause to look after our planet and its people firstly.

It is a sign of intelligence to ask the question, " is there life out there? "

The most intelligent answer has always been yes.

You seem to have a issue with spending money on pure science. What do you think pure science is taking money away from? Bombs and tanks is the most logical thing that would come to my mind. Obviously it is not going to go for education.

I want to know, I don't like guessing. Guessing usually gets me in trouble. My best guess is there is lots of life, but it is still only a guess. Sitting on this rock, fighting over little pieces paper isn't much of a life in the end. It is not something intelligent life does.

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You seem to have a issue with spending money on pure science. What do you think pure science is taking money away from? Bombs and tanks is the most logical thing that would come to my mind. Obviously it is not going to go for education.

I want to know, I don't like guessing. Guessing usually gets me in trouble. My best guess is there is lots of life, but it is still only a guess. Sitting on this rock, fighting over little pieces paper isn't much of a life in the end. It is not something intelligent life does.

Yes good point i wonder if the answer to if we are alone or not really matters. What good would it do if we were confirmed to be alone or not anyway. On a self extinction catergory We are war faring species. Our lives are short.

I cant see how a measure of life in outer space will change this at all. We might stumble across life and it starts communications what are we to say and do? well thats a guess too.

One day unfolds into the next even though we cant see one billionth of a second into the future.

Heres some neat science fiction

http://www.discovery.com/tv-shows/other-shows/videos/stephen-hawkings-universe-alien-grazers.htm

http://www.discovery.com/tv-shows/other-shows/videos/stephen-hawkings-universe-our-interstellar-future.htm

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I don't really see why this is a problem. If there's oxygen in a planet's atmosphere and methane in its moon's atmosphere, then there will be a period at extremely regular intervals when the methane signature vanishes as the moon passes behind the planet. Obviously, no scientist worthy of his job description would say that a result this important had been conclusively proven until it had been checked many, many times. The basic method of detecting exoplanets already involves spotting the very slight periodic dimming of a star as planets pass in front of it; all you need to do is apply the same technique to the planet itself.

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I don't really see why this is a problem. If there's oxygen in a planet's atmosphere and methane in its moon's atmosphere, then there will be a period at extremely regular intervals when the methane signature vanishes as the moon passes behind the planet.

There are two problems with your idea.

The first is that you would have to observe one exoplanet almost permanently for long periods of time in order to detect the regular drop in the methane signature. With over 1700 exoplanets already discovered and new satellites and ground-based telescopes under construction that will increase that figure many fold there simply is not the instrument time to spend on a single planets in this way.

The second problem is that you assume that the Earth, the exoplanet and the exomoon will be perfectly aligned so that the moon will always pass behind the planet. in many cases this will only occur during certain parts of the exoplanet's orbit around the star. For most of it's orbit the exomoon will (from Earth's point of view) pass above or below the planet rather than being occulted by it. In many cases there will no occultation at all.

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