Life on another Planet? Gliese 581d

[peter grimes]

For starters, only send robots. Like we're doing currently in our own solar system. But it's not foolproof.

I have a nagging fear that the first evidence of life beyond earth will be DNA-based, and will be closely related to some bacteria here on earth. Contamination, whether by us or by natural means.

In other words, this sort of discovery won't shed any light on the possibility of life arising more than once.

 

[LucyDuke]

I think if what we find is similar to what we have, it's very likely contamination. It doesn't take very long for populations to diverge completely, even if they have the same origin. That's just wrt to the actual genetic sequences. I expect that what we find will be wildly different from what we have.

 

[Abaddon]

For starters, only send robots. Like we're doing currently in our own solar system. But it's not foolproof.

I have a nagging fear that the first evidence of life beyond earth will be DNA-based, and will be closely related to some bacteria here on earth. Contamination, whether by us or by natural means.

In other words, this sort of discovery won't shed any light on the possibility of life arising more than once.

We could end up stuck with the "bacteria from a meteorite" theory.. which doesn't help us with the actual origin of life at all

 

[LucyDuke]

It's something new, though. If we find something that appears related to what we've got, and we can rule out having contaminated it ourselves (with the spaceship), then we no longer assume life on Earth originated on Earth. That's interesting! Frustrating, yes, but interesting.

 

[Abaddon]

Do we assume it originated on earth? I thought it was a more popular idea that we got seeded by a meteorite?

 

[LucyDuke]

I'm not sure which is more popular. I wouldn't expect it to be panspermia, since that involves an unnecessary passing of the buck. I see no reason to believe anything else is more likely than Earth having its own abiogenesis.

 

[Abaddon]

Well that is also true. Either way, poking around another planet with the potential to have life can old help.

Hows our search for ice on the moon going anyway? Why isn't there algae in that moon ice?

 

[classical_hero]

I just love the speculation being done in this thread.

 

[emzie]

I just love the speculation being done in this thread.

And I just adore your speculations outside this thread.

 

[LucyDuke]

There's almost no speculation being done in this thread.

 

[Millman]

Then there's philosophical arguments like what do other life forms believe in? "Is intelligence only one form of life out there."

If there's other intelligent life out there I agree with Hawking and the other physicists that we should wait before making contact. While they might be intelligent enough to easily detect us we might start something if they are not looking.

There is a fiction book sending two alien cultures into war at the discovery of humanity. But in reality there's no telling what will happen until it does.

On the other side of the coin we could not only be lucky in having at least one habitable planet in our solar system, but also being alone. That would mean we get the entire universe to ourselves.

No matter what the scenario it's more important to make peace with one another and yourself before really exploring space for any reason imo.

Imagine a universe without light or oxygen or even the third dimension. We should be happy and lucky we have natural people and places complex enough and diverse enough to want to explore them.

 

[emzie]

For starters, only send robots. Like we're doing currently in our own solar system. But it's not foolproof.

I have a nagging fear that the first evidence of life beyond earth will be DNA-based, and will be closely related to some bacteria here on earth. Contamination, whether by us or by natural means.

In other words, this sort of discovery won't shed any light on the possibility of life arising more than once.

Robots, as you said, aren't fool proof. Bacteria have survived intentional and unintentional exposure to space for years at a time. I have a hard time imaging a truly foolproof system to eradicate any and all microorganisms, so a probe that wants to test extraterrestrial soil needs to be able to rule out contamination.

I think much of your fear is unwarranted. First, being DNA or RNA-based alone doesn't mean it must be of Earth. We don't have enough data points to know if either form of genetic coding is unique or uncommon, seeing as we have a single data point at the moment. However, doing a comparison between DNA life found on say, Europa and the stuff we have on Earth should demonstrate if there's no link. Second, we have the ability to determine how closely related two species are through genetics. If we find something that is DNA based and we run it against current earth specimens and get a return of 3 billion years, that could mean that it's of Earth origin but was ejected 3 billion years ago by an impact event, and thus proves the ability of microbes to travel through space. Or... it could just happen to have no ancestor more recent than 3 billion years with any of the species compared, but we didn't test enough bacteria. We're no where near close to cataloguing all the species of life on this planet to rule out that possibility. People have been to name more than a thousand new species of bacteria merely by taking random samples of ocean water in exotic locals like Italy.

Personally, I'd find a really cool result being we share an ancestor with microbes on say, Europa, but that ancestor is too far back into Earth's history for it to have originated here. That's a small window though, smaller than the error bars you'd have at such an age.

 

[Millman]

Another speculation is that we might be some left over advanced aliens science project. I'm sure Futurama has an ep. about that.

I argue the right set of circumstances. Be it unintentional or not. If we are lucky enough to live to the time we can know the truth on these matters.

 

[emzie]

Another speculation is that we might be some left over advanced aliens science project. I'm sure Futurama has an ep. about that.

I argue the right set of circumstances. Be it unintentional or not. If we are lucky enough to live to the time we can know the truth on these matters.

Anything short of an award issued to Slartibartfast would leave me skeptical of alien seeding. Okay, perhaps finding life outside the solar system that shared common descent with earth-based life, with a last common ancestor older than either planetary body would make me take notice.

 

[peter grimes]

Robots, as you said, aren't fool proof. Bacteria have survived intentional and unintentional exposure to space for years at a time. I have a hard time imaging a truly foolproof system to eradicate any and all microorganisms, so a probe that wants to test extraterrestrial soil needs to be able to rule out contamination.

I can't think of anything foolproof either, the closest I can come is having something assemble itself from material that's far from earth (asteroid belt? oort cloud?). But even that isn't a guarantee.

First, being DNA or RNA-based alone doesn't mean it must be of Earth. We don't have enough data points to know if either form of genetic coding is unique or uncommon, seeing as we have a single data point at the moment.

See, I interpret the data point as being the opposite: ALL of the life we know is DNA based - we've never found any that's not. It could be that we don't know how to look for it, for one.

All Life As We Know It (ALAWKI) also has a specific chirality, not to mention a very limited vocabulary of amino acids. I think a stronger argument for non-earth related DNA would be from DNA that is fundamentally different from Earth's - fundamentally incompatible.

If we find something that is DNA based and we run it against current earth specimens and get a return of 3 billion years...

It would be very tough to arrive at a hard and fast conclusion due to the unknown behavior of molecular clocks off-earth. As it is there's already a bit of controversy about how reliable this relative dating technique is the further back in time you look. It works well for a relative ordering, but not necessarily for an absolute date.

Personally, I'd find a really cool result being we share an ancestor with microbes on say, Europa, but that ancestor is too far back into Earth's history for it to have originated here.

I see this as being a very dissatisfying possibility: it won't bring us any closer to figuring out how life arose on earth, or if it's possible to arise somewhere else.

My personal belief is that life did indeed arise here on earth, and terran microbes have been transported within the solar system, and that life has arisen independently in places not only in the universe but also in the galaxy.

 

[r_rolo1]

See, I interpret the data point as being the opposite: ALL of the life we know is DNA based - we've never found any that's not. It could be that we don't know how to look for it, for one.

All Life As We Know It (ALAWKI) also has a specific chirality, not to mention a very limited vocabulary of amino acids. I think a stronger argument for non-earth related DNA would be from DNA that is fundamentally different from Earth's - fundamentally incompatible.

Well, the chirality is about right , but there are some more exotic forms of bacteria in our planet that use some very wierd aminoacids ( especially the thermophile bacterias ) and there are some bacteria that use diferent bases for their DNA ( not mentioning the theory that states that DNA is not the original genetic material of life on earth ... ).

To be honest, ( and I say this behind my BioChemistry degree ) if we found anything that resembles DNA in other planet I would assume that it was terran contamination until proven otherwise, no matter where it would be found. I can imagine thousands of molecules that could make the role of carrying genetic material and that are not DNA or even similar, so getting any DNA out there from independent evolution is of crazy low odds.

It would be very tough to arrive at a hard and fast conclusion due to the unknown behavior of molecular clocks off-earth. As it is there's already a bit of controversy about how reliable this relative dating technique is the further back in time you look. It works well for a relative ordering, but not necessarily for an absolute date.

Well, it would obviously not work ... it barely works here on earth. The genetic mutation clock is a direct function of the ammount of radiation that can alter DNA that strikes the surface of the planet in question ( and of the average temperature ), and that is not even constant on this planet. OFC there are some absolute maximums in the area ( say, you can't have more than 20% mutation per generation in average, because it would be certain that it would shot some critical part of the DNA and make it unable to reproduce in 1 or 2 generations ... and even then only virus in earth can cone close of that ) but any datation from that method would need to be taken with a huge grain of salt

I see this as being a very dissatisfying possibility: it won't bring us any closer to figuring out how life arose on earth, or if it's possible to arise somewhere else.


My personal belief is that life did indeed arise here on earth, and terran microbes have been transported within the solar system, and that life has arisen independently in places not only in the universe but also in the galaxy.

Well, I would not be the least surprised if our life had started in Mars or Venus and then brought here via meteorite ( it is widely known that the three planets exchange lumps of rock with some consistency due to meteorite blasts that blow planetary material to outer space ), but in the end you are right: it would be simply tossing the problem to other planet if we simply state that life started on mars/venus . Not that it would not solve the fossile gap ...

 

[Bootstoots]

Ack! I meant to reply to this thread, but I forgot to.

Anyway, I think your math is probably right, contre. But I don't think you have to be able to resolve the disk of a planet in order to analyze its light. Keep in mind that we can't visually resolve any star we see with our naked eye, but we still see several thousand of them as point sources of light. I don't see any reason that we wouldn't be able to analyze the spectra of objects that appear in telescopes as point sources. The trick is in somehow subtracting out the light of the parent star so we can directly see the planet at all, and that's what I'm not sure if we're getting close to being able to do.

 

[emzie]

We can resolve some of them. This is Betelgeuse from Hubble. I imagine it's been cleaned up though in photoshop. Of course the star would fully envelop Jupiter's orbit in the solar system. It's rather big.

Spoiler :

But anyway, yeah, it should be possible to block out the light from the star while not blocking out the whole system. You'd then be able see planets positioned right and if enough light is reflected off, or they're emitting brightly in say infrared.

Of course, those are some very very big ifs.

 

[choxorn]

It might be, but the problem is, even close star systems are so far away that the system occupies only a very slightly larger viewing field than the star does. Blocking out the star but not the system would require both a crazy amount of precision and the ability to see the light from planets in other star systems in the first place, neither of which we can really do right now.

 

[emzie]

It might be, but the problem is, even close star systems are so far away that the system occupies only a very slightly larger viewing field than the star does. Blocking out the star but not the system would require both a crazy amount of precision and the ability to see the light from planets in other star systems in the first place, neither of which we can really do right now.

Continent-spanning radio telescope arrays can do .001 arcseconds, an order of magnitude better than my hypothetical 10m optical in orbit. I can imagine the precision at least.