Could aliens be on earth?

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Could aliens be on earth?

Post by lpm » Mon Jan 06, 2020 12:45 pm

Some idiot who was once transported into space has made headlines (in the Daily Star) by saying aliens could be living here on earth.

By which it seems she meant non-carbon based microbes.

- Is it still believed there can be boron-based or silicon-based life?
- Surely we'd have noticed the effects of such life, in their waste products say?
- Could there be such life deep underground where we carbon-based lifeforms have never explored?
- Could known life be an ancient merger of earth-born replicators and inter-stellar imports of other replicators?

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Re: Could aliens be on earth?

Post by AMS » Thu Jan 09, 2020 10:49 pm

Flicking through the wiki page on hypothetical alternative biochemistries, it says boron wouldn't work in our oxygen-based atmosphere.

Also, it makes the point that silicon is about 1000x as abundant as carbon in the accessible bits of the earth, yet life here is carbon based, which raises some doubts about whether silicon could actually work.

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Re: Could aliens be on earth?

Post by bjn » Thu Jan 09, 2020 11:03 pm

AMS wrote:
Thu Jan 09, 2020 10:49 pm
Flicking through the wiki page on hypothetical alternative biochemistries, it says boron wouldn't work in our oxygen-based atmosphere.

Also, it makes the point that silicon is about 1000x as abundant as carbon in the accessible bits of the earth, yet life here is carbon based, which raises some doubts about whether silicon could actually work.
The problem with a silicon is that it oxidises to sand, which tends to clog up yer lungs.

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Re: Could aliens be on earth?

Post by Boustrophedon » Fri Jan 10, 2020 12:14 am

I'll just point to Betteridge's law of headlines.
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Re: Could aliens be on earth?

Post by Fishnut » Fri Jan 10, 2020 12:39 am

lpm wrote:
Mon Jan 06, 2020 12:45 pm
Some idiot...
Could we please stop with the ableist slurs? They're completely unnecessary and hugely derogatory. Just because someone says something you don't agree with doesn't make them an idiot. This isn't directed just at lpm. "Idiot" and "stupid" appear to have become the go-to insult on this forum and it's really pissing me off. Even if someone is an idiot doesn't that mean we should be more patient, and not throw their perceived intellectual inferiority in their face? If I was someone coming here for the first time to learn and wasn't supremely confident I'd be instantly put off. I thought we were trying to attract new people, not alienate them by acting like intellectually superior a..eholes.0

As to Helen Sharman, she was talking in a regular "fluff" feature in the Observer, and said,
Aliens exist, there’s no two ways about it. There are so many billions of stars out there in the universe that there must be all sorts of different forms of life. Will they be like you and me, made up of carbon and nitrogen? Maybe not. It’s possible they’re here right now and we simply can’t see them.
That seems like a pretty fair statement followed by some speculation that's hedged. I'm not sure why it's inspired such opprobrium. Maybe it's not just the tabloids going for faux outrage.

Personally, I'm more outraged at the Daily Star calling a 56 year old doctor of chemistry a "girl".
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Re: Could aliens be on earth?

Post by dyqik » Fri Jan 10, 2020 1:30 am

Well said.

There's absolutely nothing new or controversial in what she said. It's exactly the same as you'd hear from any astronomer/exobiologist asked the same question.

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Re: Could aliens be on earth?

Post by Martin_B » Fri Jan 10, 2020 7:09 am

AMS wrote:
Thu Jan 09, 2020 10:49 pm
Flicking through the wiki page on hypothetical alternative biochemistries, it says boron wouldn't work in our oxygen-based atmosphere.

Also, it makes the point that silicon is about 1000x as abundant as carbon in the accessible bits of the earth, yet life here is carbon based, which raises some doubts about whether silicon could actually work.
Life around subsea volcanic vents uses methane, hydrogen sulphide, and other, non-oxygen-based compounds to sustain life.

IIRC, one issue with silicon-based life is the high activation energies required for chemical reactions. But I am trying to remember something taught ~30 years ago.
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Re: Could aliens be on earth?

Post by Tessa K » Fri Jan 10, 2020 9:55 am

Yes, we are here.

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Re: Could aliens be on earth?

Post by lpm » Fri Jan 10, 2020 10:30 am

dyqik wrote:
Fri Jan 10, 2020 1:30 am
There's absolutely nothing new or controversial in what she said. It's exactly the same as you'd hear from any astronomer/exobiologist asked the same question.
But do these astronomers/exobiologists say it in a "can't say it's impossible" way, not ruling it out even though they think it's incredibly unlikely? Or do they say it in a genuine maybe way?

For dark matter we could see the effects first, then we try to figure out what it's made of. If there was dark biology on earth, why wouldn't we be seeing the effects? We can see the legacy of microbes that lived 4 billion years ago and the impact of incredibly rare extremophiles. Anything that processes energy becomes food for other lifeforms, so why wouldn't we carbon-DNAers exploit and be exploited by the unknown biology? Carbon-DNAers created the atmosphere and much of the rock on the planet, yet there could be a dark biology that does nothing? Where's the equivalent of the gravitational pull?
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Re: Could aliens be on earth?

Post by shpalman » Fri Jan 10, 2020 11:01 am

Martin_B wrote:
Fri Jan 10, 2020 7:09 am
AMS wrote:
Thu Jan 09, 2020 10:49 pm
Flicking through the wiki page on hypothetical alternative biochemistries, it says boron wouldn't work in our oxygen-based atmosphere.

Also, it makes the point that silicon is about 1000x as abundant as carbon in the accessible bits of the earth, yet life here is carbon based, which raises some doubts about whether silicon could actually work.
Life around subsea volcanic vents uses methane, hydrogen sulphide, and other, non-oxygen-based compounds to sustain life.

IIRC, one issue with silicon-based life is the high activation energies required for chemical reactions. But I am trying to remember something taught ~30 years ago.
What my A-level chemistry teacher said, was that you just don't get long-chain Si compounds.
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Re: Could aliens be on earth?

Post by science_fox » Fri Jan 10, 2020 11:14 am

shpalman wrote:
Fri Jan 10, 2020 11:01 am

What my A-level chemistry teacher said, was that you just don't get long-chain Si compounds.
Poly-siloxanes and the like are quite common now. Sealants and rubber analogues and the like. They may not be at the DNA length, but they're into small-protein mass range easily.
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Re: Could aliens be on earth?

Post by dyqik » Fri Jan 10, 2020 11:38 am

lpm wrote:
Fri Jan 10, 2020 10:30 am
dyqik wrote:
Fri Jan 10, 2020 1:30 am
There's absolutely nothing new or controversial in what she said. It's exactly the same as you'd hear from any astronomer/exobiologist asked the same question.
But do these astronomers/exobiologists say it in a "can't say it's impossible" way, not ruling it out even though they think it's incredibly unlikely? Or do they say it in a genuine maybe way?
Depends on how much time they are given to say it, and whether the question is sprung on them in a different context, who's asking, etc.

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Re: Could aliens be on earth?

Post by lpm » Fri Jan 10, 2020 11:43 am

How about if their profession is communicating science to the public and they have 30 years expertise in dealing with tabloids and the mass media?
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Re: Could aliens be on earth?

Post by Gfamily » Fri Jan 10, 2020 11:46 am

I refer to Clarke's first law
Arthur C Clarke wrote:When a distinguished but elderly* scientist states that something is possible, they are almost certainly right. When they state that something is impossible, they are very probably wrong.

* ahem, over 30 for Physics, Maths, Astrophysics
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Re: Could aliens be on earth?

Post by Tessa K » Fri Jan 10, 2020 12:52 pm

lpm wrote:
Fri Jan 10, 2020 11:43 am
How about if their profession is communicating science to the public and they have 30 years expertise in dealing with tabloids and the mass media?
Even then there is a tendency to wilfully misquote to get a good headline.

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Re: Could aliens be on earth?

Post by sheldrake » Fri Jan 10, 2020 1:30 pm

lpm wrote:
Fri Jan 10, 2020 10:30 am
dyqik wrote:
Fri Jan 10, 2020 1:30 am
There's absolutely nothing new or controversial in what she said. It's exactly the same as you'd hear from any astronomer/exobiologist asked the same question.
But do these astronomers/exobiologists say it in a "can't say it's impossible" way, not ruling it out even though they think it's incredibly unlikely? Or do they say it in a genuine maybe way?

For dark matter we could see the effects first, then we try to figure out what it's made of. If there was dark biology on earth, why wouldn't we be seeing the effects? We can see the legacy of microbes that lived 4 billion years ago and the impact of incredibly rare extremophiles. Anything that processes energy becomes food for other lifeforms, so why wouldn't we carbon-DNAers exploit and be exploited by the unknown biology? Carbon-DNAers created the atmosphere and much of the rock on the planet, yet there could be a dark biology that does nothing? Where's the equivalent of the gravitational pull?
One of the mainstream hypotheses for how life started on earth was the arrival of organic molecules in comet impacts, but I don't think they go as far as saying those organic molecules came from actual living organisms.

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Re: Could aliens be on earth?

Post by shpalman » Fri Jan 10, 2020 1:51 pm

sheldrake wrote:
Fri Jan 10, 2020 1:30 pm
lpm wrote:
Fri Jan 10, 2020 10:30 am
dyqik wrote:
Fri Jan 10, 2020 1:30 am
There's absolutely nothing new or controversial in what she said. It's exactly the same as you'd hear from any astronomer/exobiologist asked the same question.
But do these astronomers/exobiologists say it in a "can't say it's impossible" way, not ruling it out even though they think it's incredibly unlikely? Or do they say it in a genuine maybe way?

For dark matter we could see the effects first, then we try to figure out what it's made of. If there was dark biology on earth, why wouldn't we be seeing the effects? We can see the legacy of microbes that lived 4 billion years ago and the impact of incredibly rare extremophiles. Anything that processes energy becomes food for other lifeforms, so why wouldn't we carbon-DNAers exploit and be exploited by the unknown biology? Carbon-DNAers created the atmosphere and much of the rock on the planet, yet there could be a dark biology that does nothing? Where's the equivalent of the gravitational pull?
One of the mainstream hypotheses for how life started on earth was the arrival of organic molecules in comet impacts, but I don't think they go as far as saying those organic molecules came from actual living organisms.
Depends how interesting those organic molecules were, but they would still need to have formed somewhere in the first place, it just shifts the question of where. https://en.wikipedia.org/wiki/Panspermia
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Re: Could aliens be on earth?

Post by sheldrake » Fri Jan 10, 2020 2:32 pm

shpalman wrote:
Fri Jan 10, 2020 1:51 pm
sheldrake wrote:
Fri Jan 10, 2020 1:30 pm
lpm wrote:
Fri Jan 10, 2020 10:30 am

But do these astronomers/exobiologists say it in a "can't say it's impossible" way, not ruling it out even though they think it's incredibly unlikely? Or do they say it in a genuine maybe way?

For dark matter we could see the effects first, then we try to figure out what it's made of. If there was dark biology on earth, why wouldn't we be seeing the effects? We can see the legacy of microbes that lived 4 billion years ago and the impact of incredibly rare extremophiles. Anything that processes energy becomes food for other lifeforms, so why wouldn't we carbon-DNAers exploit and be exploited by the unknown biology? Carbon-DNAers created the atmosphere and much of the rock on the planet, yet there could be a dark biology that does nothing? Where's the equivalent of the gravitational pull?
One of the mainstream hypotheses for how life started on earth was the arrival of organic molecules in comet impacts, but I don't think they go as far as saying those organic molecules came from actual living organisms.
Depends how interesting those organic molecules were, but they would still need to have formed somewhere in the first place, it just shifts the question of where. https://en.wikipedia.org/wiki/Panspermia
It does. iirc the panspermia hypothesis is based on the idea that some of the original synthesis of these moleculues might be more likely in unusual conditions found in space.

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Re: Could aliens be on earth?

Post by Gfamily » Fri Jan 10, 2020 3:33 pm

sheldrake wrote:
Fri Jan 10, 2020 2:32 pm
shpalman wrote:
Fri Jan 10, 2020 1:51 pm
Depends how interesting those organic molecules were, but they would still need to have formed somewhere in the first place, it just shifts the question of where. https://en.wikipedia.org/wiki/Panspermia
It does. iirc the panspermia hypothesis is based on the idea that some of the original synthesis of these moleculues might be more likely in unusual conditions found in space.
I'm not an expert on astrochemistry, but I don't think there are any particularly exceptional circumstances required to generate even quite complex molecules or radicals. We've seen the evidence for basic components (water, methane, ethane, CO2, NO2 etc) forming tholins (a mix of polymers) on the surfaces of bodies irradiated with UV or cosmic rays.
Yes, unusual for Earth, but not unusual in space.
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Re: Could aliens be on earth?

Post by Boustrophedon » Fri Jan 10, 2020 8:56 pm

This was Fred Hoyle's idea first, I think? Most commentators think he started taking his work of fiction "The Cloud" way too seriously.

Complex molecules have been detected in interstellar space, from absorption spectra, but near a sun with lots of hard ultra violet none survive. I think given that the same proto life chemicals have been detected near hydrothermal vents in the deep ocean, Occam's razor comes into play.
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Re: Could aliens be on earth?

Post by Boustrophedon » Fri Jan 10, 2020 8:59 pm

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Re: Could aliens be on earth?

Post by Gfamily » Fri Jan 10, 2020 9:24 pm

Boustrophedon wrote:
Fri Jan 10, 2020 8:56 pm
This was Fred Hoyle's idea first, I think? Most commentators think he started taking his work of fiction "The Cloud" way too seriously.

Complex molecules have been detected in interstellar space, from absorption spectra, but near a sun with lots of hard ultra violet none survive. I think given that the same proto life chemicals have been detected near hydrothermal vents in the deep ocean, Occam's razor comes into play.
I can see that hard UV radiation in free space is very likely to be destructive of complex radicals, but with surfaces it can equally allow construction (as with tholins) - and we have seen them on the surface of Pluto and other far solar system objects.
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Re: Could aliens be on earth?

Post by Fishnut » Fri Jan 10, 2020 9:55 pm

This is a good piece that points out the problems with looking for other forms of life and then discusses why silicon-based life would be hugely difficult (but not entirely impossible) to evolve on earth.

I really like how they discuss the problem with defining life. Biology is not an area where absolute definitions are possible. I remember having to learn about 30 different definitions of a "species" for my masters, and that was only a subset of all the definitions out there. Trying to find a definition that covers birds and bacteria is not at all straightforward. Same with a definition that covers both living and extinct organisms. "Life" has similar problems - there's always something that will manage to defy the rules. And as the piece says,
Not being able to define life other than “we’ll know it when we see it” means we are truly limiting ourselves to geocentric, possibly even anthropocentric, ideas of what life looks like.
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Re: Could aliens be on earth?

Post by jimbob » Sat Jan 11, 2020 11:14 pm

Fishnut wrote:
Fri Jan 10, 2020 9:55 pm
This is a good piece that points out the problems with looking for other forms of life and then discusses why silicon-based life would be hugely difficult (but not entirely impossible) to evolve on earth.

I really like how they discuss the problem with defining life. Biology is not an area where absolute definitions are possible. I remember having to learn about 30 different definitions of a "species" for my masters, and that was only a subset of all the definitions out there. Trying to find a definition that covers birds and bacteria is not at all straightforward. Same with a definition that covers both living and extinct organisms. "Life" has similar problems - there's always something that will manage to defy the rules. And as the piece says,
Not being able to define life other than “we’ll know it when we see it” means we are truly limiting ourselves to geocentric, possibly even anthropocentric, ideas of what life looks like.

I think that the problem of identifying life is similar to the discussion about abiogenesis. And in the more general discussion about life, we already have known examples of not-organisms (um, systems?) that are subject to natural selection and Darwinian evolution whilst not being alive - most obviously, viruses, but possibly particular folded versions of prion proteins too.

Coming back to this, it's quite plausible to imagine a proto-life where collections of proteins in a membrane imperfectly self-replicate given the right chemical environment, and that these would thus be subject to natural selection even though they don't independently reproduce. If some descendent starts preferentially taking in* the raw materials (given the right external environment) then, I guess that would be the start of a metabolism. There wouldn't be any sensing or movement but there would be growth and something akin to a metabolism and excretion.

Such a descendant would presumably have a selective advantage over those versions that just rely on the correct chemical gradients, and so its descendants would presumably experience a selective pressure to increase the utilisation of the raw materials - moving the successful descendants closer what was more obviously a metabolism and a more adapted excretion. Sensory response and then movement could evolve after this.


Returning to the idea of a shadow silicon biosphere on Earth. I can imagine a machine life that imperfectly self-replicates, but I'd struggle with any type of life that doesn't have some analogue of metabolism.

If such silicon-based microorganisms (I'm assuming that trolls are fiction) existed, and utilised the plentiful silica available, I'd have expected it to have left a chemical signature in a similar way to the oxygen signature on earth, or coal and oil. That would suggest that at the most, it's very rare and limited in its environments where it can live.

Or it's the limitations of my understanding as a non-biologist.

*I suppose viruses outsource the problem of metabolism to their host cell, and their resources are external to the viruses.
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Re: Could aliens be on earth?

Post by Fishnut » Sat Jan 11, 2020 11:29 pm

There's an excellent book called What is Life? How Chemistry Becomes Biology by Addy Pross that asks and attempts to answer some of those questions. I can't remember too much about it as I read it a while ago but I do recommend it. As a non-biochemist I found it accessible.
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