NASA Asks: Will We Know Life When We See It? (nasa.gov) 155
In the last decade, we have discovered thousands of planets outside our solar system and have learned that rocky, temperate worlds are numerous in our galaxy. The next step will involve asking even bigger questions. Could some of these planets host life? And if so, asks NASA, will we be able to recognize life elsewhere if we see it? From a blog post on NASA's website: A group of leading researchers in astronomy, biology and geology has come together under NASA's Nexus for Exoplanet System Science, or NExSS, to take stock of our knowledge in the search for life on distant planets and to lay the groundwork for moving the related sciences forward.
"We're moving from theorizing about life elsewhere in our galaxy to a robust science that will eventually give us the answer we seek to that profound question: Are we alone?" said Martin Still, an exoplanet scientist at NASA Headquarters, Washington. In a set of five review papers published last week in the scientific journal Astrobiology, NExSS scientists took an inventory of the most promising signs of life, called biosignatures. The paper authors include four scientists from NASA's Jet Propulsion Laboratory in Pasadena, California. They considered how to interpret the presence of biosignatures, should we detect them on distant worlds. A primary concern is ensuring the science is strong enough to distinguish a living world from a barren planet masquerading as one.
"We're moving from theorizing about life elsewhere in our galaxy to a robust science that will eventually give us the answer we seek to that profound question: Are we alone?" said Martin Still, an exoplanet scientist at NASA Headquarters, Washington. In a set of five review papers published last week in the scientific journal Astrobiology, NExSS scientists took an inventory of the most promising signs of life, called biosignatures. The paper authors include four scientists from NASA's Jet Propulsion Laboratory in Pasadena, California. They considered how to interpret the presence of biosignatures, should we detect them on distant worlds. A primary concern is ensuring the science is strong enough to distinguish a living world from a barren planet masquerading as one.
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Just like all physics: we theorise, we predict, we observe.
Predict: by current theory, spectral lines of elements on earth should be "this".
Observe: yep, that seems to be true on earth.
Predict: the universe is pretty boring, same rules everywhere, so spectral lines will be the same everywhere, plus (consistent) red/blue shift because stuff is moving (and we can predict that too, with current theory).
Observe: look at distant objects and what do you see... crikey jingo, it matches the prediction.
Sure you coul
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Of course they will be. So let's proceed to other planets, presuming that all lifeforms will consist of the exact same elements that we do.
Can't see any problem with that methodology.
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presuming that all lifeforms will consist of the exact same elements that we do.
Can't see any problem with that methodology.
Sounds like you cannot see the reasons for it either.
It is a reasonable presumption that *most* life will use the same simple elements that earth-life does, and so that is what we should be looking for.
There are other theoretical chemistries or more exotic bases for self-replicating things, but they would be far more difficult to begin.
Silicon chips don't self-assemble, even over billions of years and planets. Water has some very special properties not shared by other simple, common chemicals found in the
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Water is unique among small molecules. But there is some possibility I think that ammonia might be a suitable solvent for a different type of carbon-based life. They are both small polar molecules that are abundant, are often liquid over temperature ranges compatible with organics, and are both excellent solvents.
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There was a SciFi story that sort of riffed on that idea. The aliens in the story came from a parallel universe. I think the Periodic Table was the same, but some details were different--the exact frequency of light put out by lasers was different, for example, because the Fine Constant (or something like it) was subtly different. (And maybe Tellurium and Iodine (and Potassium and Argon, Nickel and Cobalt), had the atomic weights that would have ordered them correctly in Mendeleev's table.)
Found it: Anat
Obligatory Star Trek (Score:5, Interesting)
It's life, Jim, but not as we know it. - Dr. McCoy
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Ah we come in peace.
Shoot to kill. Shoot to kill. Shoot to kill.
Ah we come in peace.
Shoot to kill, men.
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Hah. I didn't expect this reference here...
(for those wondering, ti's a Dr. Demento show song - Star Trekkin'. I think I found a copy off the Internet Archive.
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McCoy was talking about Spock.
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McCoy's line was - "He's dead Jim."
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The only Starfleet captain who has ever boldly gone somewhere is captain Picard.
The meaning of life... (Score:2)
I predict--- The meaning of life will keep changing as we make discoveries throughout the timeline of mankinds exploration.
We barely recognize it here (Score:5, Insightful)
The line between life and not-life is already indistinct here on Earth. Viruses? Not-life...quite. Kinda life?
And forget trying to figure out what counts as intelligent life. Trees communicate with an underground fungus network and through signals in the air, can probably feel pain, count and learn, but we're not quite at the point of calling them 'intelligent'. Birds turn out to be incredibly intelligent, but people are still reluctant to admit the level of intellect the birds have, and how deep it may actually go.
What hope do we have of classifying an indistinct gas-being that gets by just fine when we're not around, but immediately decoheres the moment a human passes through them waving their hand in front of their face? Or some sort of super-cooled snow creature with liquid nitrogen in its veins that reacts too slowly for us to even comprehend?
Life definition (Score:3)
Simplish version: A complex system, constructed and guided by a conserved information pattern, which acts so as to sustain itself (and by "itself" we mean a causally-connected sequence and/or group of instances of its constrained system pattern.)
Bafflegab-level Detail:
A Matter/energy system which embodies/contains a particular (that is, constrained in variation) complex information pattern. When processed by the matter/energy system, the information pattern constructs instances of the system, and by constra
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By that definition, viruses would count, and like I said, those are already up in the air. But maybe you fall on the side of 'viruses are life', which is a perfectly legit position to stake out, IMO.
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Viruses 'evolve' with genetic variation, this makes them life. Living things must have the ability to replicate and have random mutations over time that lead to diversity, etc. Think of a living thing that does not possess this quality.
Re:not evolving (Score:4, Insightful)
I seem to recall a talk about sulphur-eating archaea in a hydrothermal vent environment in which no evolution has taken place for millions of years, because they've apparently reached an optimal solution (local maximum anyway) in utilizing the resources in the simple and small environment.
Evolution only works (and takes place) if you can still do better. Otherwise, you get the "surprising continuation" aspect of life without the (further) evolution aspect.
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Sharks haven't changed significantly in about 100 million years, for much the same reason--already an apex predator.
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Another non-explicitly presented aspect of the question is that NASA is not interested in finding living forms (not it has the ability to do so) but living systems. While we can argue the exact place of virus within a living-non living spectrum, there's no argument that virus-host form a living system.
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"By that definition, viruses would count"
Why they shouldn't? Within this context at least? They need another "really living" thingie to take advantage of their metabolic machine, so what?
- Hey, boss, I think that's interesting...
- What's up, Minion?
Minion: look at this. It comes from our probe at X37-ZirgggK exoplanet and looks exactly like phage T4.
Boss: Oh, no! Do you know what will happen when I present this discovery to our Science Academy? Years, if not decades, of discussions about this being a liv
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Good luck finding a tree foraging that much.
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What did you think roots were for?
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I don't know what roots are for (rethoric) but, certainly, not for foraging.
forage
ËfÉ'rÉdÊ'/
verb
gerund or present participle: foraging
(of a person or animal) search widely for food or provisions.
"the birds forage for aquatic invertebrates, insects, and seeds"
obtain (food or provisions) by searching.
"a girl foraging grass for oxen"
search (a place)
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Not without an extreme twisting of the meanings of those words they wouldn't.
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Re:Life definition and viruses (Score:3)
I think the correct way to think of viruses is to draw the boundary of the living system differently. The virus living-system comprises the virus bodies plus a spatiotemporal subset of host organisms. That is, the parts and mechanisms of the host organism that the virus uses for a period of time to perform its reproduction. The system boundary (of a living system) is the minimum boundary of a matter/energy system that can accomplish the "living" definition above. In the virus case, that boundary is bigger t
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"The line between life and not-life is already indistinct here on Earth. Viruses? Not-life...quite. Kinda life?"
Quite spot on... and shows how the question is the wrong one.
Of course, this is some of a click-bait as the question is not precisely recent, up to the point of guiding our search of exoplanets.
Of course we'll know life when we see it -that's not the question. The question is "will we know *any* kind of life when we see it?" And the answer is, of course too, we don't really know. That's why we
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Any links for that "tree count thing"? Would be interesting!
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The line between life and not-life is already indistinct here on Earth. Viruses? Not-life...quite. Kinda life?
They have heredity and replicate in their environment so I would say so.
Life might be everywhere.... can't see it? (Score:4, Insightful)
it is possible that life is everywhere, all around us in forms we don't recognize...
There are so many things that could make life unlike ours invisible. Imagine for a second a life form that's brain runs 1 billion times slower or faster than ours. Silly example to make my point: Mount Everest could be a slug, but it moves so slow that we would never know it as anything but a lifeless rock.
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perhaps Hiding Life accounts for the missing mass of the universe
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it is possible that life is everywhere, all around us in forms we don't recognize...
. . . maybe other life won't recognize us as life either . . . and instead see us as a tasty snack . . .
Re:Life might be everywhere.... can't see it? (Score:4, Funny)
it is possible that life is everywhere, all around us in forms we don't recognize...
. . . maybe other life won't recognize us as life either . . . and instead see us as a tasty snack . . .
We'll call them popplers!
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Imagine for a second a life form that's brain runs 1 billion times slower or faster than ours.
WTF? Did you mean whose?
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Imagine for a second a life form that's brain runs 1 billion times slower or faster than ours.
WTF? Did you mean whose?
Nope. I meant THAT. Whom/whose refer to PEOPLE.
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Wrong. Whose stands in for both of whom and of which/of that.
You now owe me a €10 consulting fee for teaching you something [dictionary.com] you actually could have checked on your own in 30 seconds or less and thereby not made a fool of yourself by getting caught out making shit up [lmgtfy.com].
Please make your payment for that amount within the next ten days to a charitable organisation that promotes literacy.
We appreciate your business! Välkommen åter!
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It's a nice idea, but not unexplored. You might be unaware of it, but there are people who do study things that operate on such long timescales. They're "geologists" (and a number of astronomers play in this end of the paddling pool of process rates too). Sorry, nothing wildly interesting there.
We do a fair bit of "origin of life" work too - because if there is any evidence of the origin of life
Can NASA Telescopes Get Enough Data to See Life? (Score:3)
An interesting (thought) experiment would be to determine how much data would be required to determine if there was life on Earth.
How many photons would it take for a telescope mounted spectrometer require to detect chlorophyll, C02 or other signs of life (industrial pollution) and how far away/how long would it take to collect them?
Humans are broadcasting light and radio waves from Earth, could Hubble, the James Webb telescope/other instruments detect them same amount of radiation from other solar systems?
Are there other characteristics of inhabited Earth that could be used to determine whether or not other planets have life?
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Radio waves coming from Earth require something on the order of the Arecibo dish at the orbit of Pluto to be detected. From just a few light years, away detection would be pretty much impossible. And that's for old fashioned analog broadcasts. Modern digital broadcasts are much harder to detect, since they look like broadband noise.
Our optical spectrum would probably be easier to detect from a distance.
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Our brightest "passive" emissions are our ballistic missile early warning radars. Most transmissions/emissions from Earth fade rapidly with distance. A signal that is tightly focused, powerful, and with a narrow spectrum will far outshine everything else on Earth in the electromagnetic spectrum.
So if aliens detect us from a distance they will be seeing the bright pulses of FPS-115 PAVE PAWS (Precision Acquisition Vehicle Entry Phased Array Warning System) whose signals are now 41 light years out.
These rada
Best prediction based on current observations (Score:1)
It will be large, orange, wearing yellow Tribbles on top, have small hands that move frequently, an O-shaped mouth that makes a lot of continuous and intense sounds, and rides over grass in a little vehicle containing lots of metallic sticks in a bag.
It will prefer to communicate with Earth dictators and Earth supermodels, and will spend a good deal of energy probing the limits of Earth's social media infrastructure while consuming organic materials high in lipids. It will prefer to surround itself with lar
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I had to check my finger for a tied string, then check my to-do list, in order to remember to laugh at that one.
What happens when the base chemistry changes? (Score:4, Interesting)
Our search for extraterrestrial life, such as it is, has been on the assumption that "as we know it" means carbon-based. But because right here and now we are in the early stages of a transition from carbon-based to silicon-based on Earth, what does this imply for other intelligent species?
Is this kind of change inevitable as soon as a civilization can accomplish it, and what does it mean for the possibility of communication? It could be that digitized silicon lifeforms produced by any given 'wet biology' will become good at concealing its own existence in the same way that good encryption is indistinguishable from noise.
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There are reasons rooted in the chemistry of carbon [bigpictureeducation.com] to believe that carbon-based life is more likely than anything else, like silicon. (And the practical supporting evidence that silicon is far more common in earth's crust than carbon, yet all life on earth is carbon based.)
Other bases are possible, in theory, but since there's limited resources for the search, it makes no sense to spend those resources looking for something we have no idea how to identify if we do find it, versus something familiar.
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Let's assume that this is true of the original wet biology that arises from each planet's primordial soup. Some subset of these lifeforms survives the early planetary filters to become stable technological civilizations that have curiosity beyond their immediate environment and at the same time can build silicon-based systems of increasing complexity, leading to artificial intelligence. My question is what happens when that silicon becomes a self-aware lifeform in its own right?
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I think that once/if silicon-based intelligence gets the capability to generate power for itself (e.g. building solar and wind farms and energy storage) and the capability to reliably produce copies of its host computers and networks, and the ability to defend all of that against harm, then there's no reason to say at that point that it wouldn't be life.
Carbon-based chemistry (the "wetness" of it, non-fragility of forms, versatility of variation and chaining in the chemistry and physical properties of organ
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It is of course misleading to speak of AIs as being "silicon-based". They are right now due to a particular cost-driven technological choice (eliminating GaAs for example), but our current computing technology is a transitory phase. For example, the idea of building circuits with doped carbon nanotubes is being explored now and looks like it has real potential.
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Good point - general information processors are an emergent system with a good amount of substrate-independence.
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Say that thee times quickly at Bletchley Park and you'll resurrect the unholy trio of Lovelace, Babbage and Turing.
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biochemistry is not fundamental to (a generalized but valid definition of) life.
All that is fundamental is a constrained-form complex system that is capable of continuing itself, including, by necessity probably, a capability to adapt to changing or new environments, and to adapt to competition.
Nothing in that definition mandates biochemistry.
Biochemistry is a way by which the definition can be met, and may be the only way the definition can be met in a "bootstrapping from nothing but molecules in a gravity
doubtful (Score:2)
Life at different scales... (Score:5, Insightful)
My father (who only went to school for seven years, and started working at 14, and isn't precisely highly educated) asked me the other day wether water is a pre-requisite for life. I answered as most do; yes, probably. Without some kind of solvent, reactions and material exchange is slow.
That got me thinking of scales... what if "slow" isn't a problem. What if we encounter beings with metabolism rates which are 100 000 slower or faster than ours? Would we be able to recognize it as life? Which other dimensions could scale so that we wouldn't recognize it? DeGrasse talks about intelligence - would we recognize life that is 100 000 times smarter or dumber than us? Could there be life at extreme temperatures? I don't mean 1000 deg C, I'm talking about life inside stars. There is for sure a thermal and entropy flow - could there be fusion plasma solutions to Maxwell that could make basic building blocks for something life-like? If so, could we ever observe it?
At any rate, it may be material for a star trek episode...
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That got me thinking of scales... what if "slow" isn't a problem. What if we encounter beings with metabolism rates which are 100 000 slower or faster than ours? Would we be able to recognize it as life? Which other dimensions could scale so that we wouldn't recognize it?
Exactly.
For beings with much slower metabolisms the universal speed of light wouldn't be as much of a limitation to interstellar travel, since they would perceive time more slowly, so could in theory establish functional societies on multi
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Is the universe old enough for such creatures to have evolved? It took at least 5 billion years to create us, even if you don't count the sources of the metals (in the astronomical sense) that make up the Earth and us.
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That's a thorny question. Certainly there is a question of "stellar generations", needing several cycles of material through stars to produce substantial quantities of the various different elements involved in life. If you think about stars like the Sun with a 10^10 (10 Gyr) year life span, then that becomes an issue. but since those stars tend to die quietly, they don't contribute much variety to the interstellar medium and so the next generati
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Yes, from a time perspective it seems feasible that we're not the first generation of carbon-based life (although I could just as well believe we are, at least in this part of the universe). My question was more about DrTJ's original question (a couple-three messages higher in this thread, along with Trogre's a bit lower), namely would we recognize life if its metabolism were orders of magnitude (OOM) slower than ours. DrTJ said 5 OOMs, but I guess his point would hold for smaller OOMs as well. If some p
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would we recognize life that is 100 000 times ... dumber than us?
Yes. That seemed to be a requirement for becoming the Press Secretary of the White House.
They're all around us now (Score:2)
Personal definition (Score:2)
I like the definition of life that basically says that anything that reproduces itself and evolves through natural selection is alive. That would include viruses, which would be the simplest form of life on earth.
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Process: natural selection created human generalist engineers, who created computers, computer networks, and then self-reproducing computer viruses.
So at least the "human + computer viruses" system is alive.
If computer viruses got better, and knew how to sustain their hardware and software and trick humans into helping repair their infrastructure on occasion, then maybe they would be getting close to a life definition. All, if you go back far enough, via natural selection. And if different self-modifying co
If you're in this situation (Score:2)
I don't think you'll see it either. https://vignette.wikia.nocooki... [nocookie.net]
We've been thinking about it for decades (Score:1)
Sofar (Score:2)
Will we even be able to see life? (Score:1)
Not if it sees us first, most likely.
Life in what forms? Is the better question.. (Score:3)
Microbial. Mounting evidence suggests microbial life *might* be very common. If it spends a long time dormant and comes to replicate itself only under ideal conditions, then we'll need to experiment with conditions to see if we can bring it back to life to observe..
Animal. Even if microbial life is plentiful, multicellular life seems likely to be very uncommon. We've only had it on Earth for the last half-billion years, seemingly by some freak accident.
Lingual. Dolphins and whales exhibit languages with complex grammars, refer to each other by name even gossip about each other while the other is away, have an exquisite sense of past, present, and future and yet man has only uncovered a fraction of their languages. There is no known capability of human languages that bottle nosed dolphins lack. If we cannot even hack their language, what hope is there of extra-terrestrials if ever encountered? All we need is a dolphin drone, remotely controllable with VR headset and computer translation of phonemes (both ways), in order to learn through immersion... Nobody is even trying.
Technological. To be a technological species, you need (A) dexterous manipulators, (B) social behavior, and (C) imitation learning/substitution problem solving. You cannot build things without dexterous manipulators and cannot pass along knowledge and skills without both imitation and social behavior. Imitation must be substantial enough to do without a reason for doing so. Chimpanzees imitate but do not continue with behaviors that serve no obvious purpose. Humans continue regardless... We don't seem to care what customs are for. Substitution problem solving the other side of the imitation coin. In order to imitate one person/thing for another, you need to build a mental model of each, identify similarities, and swap one for another. For example, a rock with a flat side might substitute for a hammer. This is analogy -- the essence of conceptual knowledge.
I suspect that, if celestial bodies with subsurface liquid water oceans are as common as they seem then an aquatic technological species would have a far lower bar to entry into space than a surface species, such as ours. On Earth, octopi species have requirements A and C and recently two small examples of B (social behavior) have also been found (look up "Octopolis and Octlantis"). Unlike most octopi species, they build small city-like collective settlements and the mothers live for a time simultaneously with their offspring. This strongly suggests they are building knowledge and/or at least skills across generations. It seems to me likely that species such as these could be more common than surface species, such as us. Furthermore, Pluto suggests they might more so inhabit the colder regions of space... They might even be averse to places as close to stars, as Earth is to the Sun.
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"Dolphins and whales exhibit languages with complex grammars... There is no known capability of human languages that bottle nosed dolphins lack. If we cannot even hack their language..." Putting on my linguist hat (and yes, I am a linguist), IMO, all three sentences are simply false. But under the assumption of your third clause ("we cannot even hack their language"), the second sentence and probably the first are undecidable. We can tell that there is variability in the sounds a whale makes, but that
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Animal. Even if microbial life is plentiful, multicellular life seems likely to be very uncommon. We've only had it on Earth for the last half-billion years, seemingly by some freak accident.
The appearance of animal life does not seem to be a freak accident (that would be the development of tool-making animals who also communicate symbolically). I suspect you are thinking of the endosymbiotic event that led to the Eucaryotes. But this happened a long time ago, more than 1.5 billion years. Eucaryotes remained microscopic single cell organisms for more than a billion years.
The development of animal life about 600 million years ago looks like it is tied to oxygen level of the atmosphere reaching s
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The appearance of animals with hard parts about 600 million years ago post dated the appearance of multi-cm body animals by approaching 100 Myr. At the same time eyes also appeared, and there was also a change in the phosphate chemistry of seawater - and the earliest "hard parts" of several phyla were composed of phosphates.
There are vocal advocates for all three explanatory narratives. I'm not
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The Ediacaran faunas go back to around 700 million years (but remain of "uncertain affiliation"). A number of examples from a number of regions currently widely separated going back to well over a billion years suggest mobile organisms grazing on or under microbial biofilms. Which would be early animals - though whether
"-barren planet masquerading-" (Score:1)
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This is not a reply to a wrong thread... this is a gibberish nonsense post, probably computer generated.
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Re: Not a chance... (Score:2)
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That's 1993. Publication date. The research was done in December 1990. Since then, a number of other Earth gravitational assist manoeuvres have been done by other spacecraft, and taking "ground truth" measurements as a way of checking instruments, systems and procedures remains a useful ploy.