?by Larry Klaes
Tau Zero journalist Larry Klaes here gives us a quick overview of the history and future of the Earth, so vital for understanding not only how life emerged here but how it may appear around other stars. It’s good to keep this background in mind as Kepler and COROT go planet-hunting. Thus far we’ve had our share of surprises as we’ve explored other systems, and doubtless there will be many more as future instruments come online, both in space and on the ground. And as Larry reminds us, there is much we still have to learn about our own planet.
Let’s look at our celestial home’s place in time as well as space, namely the long and ancient history of its cosmic birth and development. This story includes a general history of the wide variety of living beings that dwell just about everywhere on this planet.
Planet Formation and the Big Collision
Earth’s geological history began about five billion years ago, roughly eight billion years after the Universe got its start in the Big Bang. Back then, our planet was just another disembodied collection of dust and gas along with the rest of the Solar System in what astronomers call a nebula. It took the dramatic death of a nearby and unknown star to get our system and world started via the shockwaves of the exploding sun, also known as a supernova.
Not only did the supernova impact start condensing the interstellar dust and gas cloud that would eventually become us, that star’s death throes also infused our nebula with heavier elements that helped produce the various worlds and eventually all life on Earth. As the late Cornell astronomer Carl Sagan once famously said: “We are made of star stuff.”
The cosmic cloud that would become our Solar System began condensing and collapsing into many individual worldlets called planetesimals. As the planetesimals collided with each other as they looped around the newborn Sun amidst the nebula that was turning into a flattened disk of debris, the ones that were not destroyed by the impacts slowly built up into larger worlds. One particular collection became our Earth, though at this early stage it was essentially a sphere of molten rock, with no water and nothing living on it.
There were more planets in our Solar System during this era than there are now. Many of them were in chaotic orbits around the Sun. One of these early planets, about the size of Mars (but not the current Red Planet, please note) smashed into the young and still molten Earth, becoming almost totally vaporized in the process. Massive chunks of our world were thrown into space, then began circling Earth and eventually condensed into our Moon.
Image: Heavy bombardment from space may have caused life to ‘reboot’ multiple times. Credit and copyright: Julian Baum.
Over time our planet cooled enough so that the surface, or crust, hardened into solid rock. Water began to appear both from condensation and various comets that struck Earth, as there was still plenty of nebula debris left over from the Solar System smashing into itself and into our planet. Our Moon bears the scars of that ancient bombardment period to this day: We call them craters.
Let There Be Life
Though solid evidence for the first signs of life on Earth currently go back over 3.5 billion years, scientists think simple organisms may have started when our planet cooled and water formed on it over four billion years ago. However, these earliest living natives may have been wiped out by the relentless impacts of space debris, causing life on Earth to restart more than once. The fact that life did begin on our planet so relatively soon after its violent formation could mean that life may also have begun and exists on many other worlds throughout the Universe.
For most of the time that organisms have been on Earth, native creatures had been no more sophisticated than microorganisms, some of which gathered themselves into colonies called stromatolites. Then just over half a billion years ago, Earth’s climate underwent changes, perhaps in part due to these ancient microbes giving off oxygen for ages, which brought about what scientists call the Cambrian Explosion or Radiation. In a relatively short time geologically speaking, life grew and developed into multicellular forms which became the ancestors of the wide variety of organisms that crawl, walk, fly, and swim all over our planet, including us, humanity.
Image: This view of the shallows of Shark’s Bay, Australia, shows a colony of living stromatolites. ©Isao Inouye (University of Tsukuba), Mark Schneegurt (Wichita State University), and Cyanosite.
Though impacts from large space objects in later epochs did disrupt ecosystems and cause many extinctions – the most famous being the death of the dinosaurs 65 million years ago – life on Earth has managed to survive and thrive just about everywhere in numerous forms.
The Final Days
There will come a time in the far future, however, when all life on this planet will have to either leave or perish. Several billion years from now, our Sun will begin to expand from a yellow dwarf star into a red giant sun. Earth may escape being engulfed and vaporized by the bloating Sun, but it will become very hot, enough to evaporate the oceans and turn our planet’s surface into molten slag.
Image: A possible end for the Earth. Credit: fsgregs/Wikimedia Commons.
Eventually, the Sun will shrink and cool down into a white dwarf star and later a dead cinder of itself. Earth will become a barren, frozen, and dark place and may one day drift off into interstellar space, no longer held in place by the remnant mass of the Sun. Hopefully long before our Sun comes to the end of its life, our very distant descendants will have left Earth and the Solar System to start new lives in other parts of the galaxy.
The K/T extinction might have been caused by an impact, but the evidence that the other mass extinctions were impact caused is a lot more shaky. Volcanic eruptions seem to be strongly implicated in several of the other ones, and various other causes seem probable. Catastrophe from the stars is not the only way to wipe out large numbers of species, it would seem…
Heh — this sentence will give any creationist who drop in fits.
I tend to agree with it, but I’m also of a mind that the next sentence is where the much of the uncertainty is:
Four billion years, give or take, is an awfully long time and may be a clue–along with the half-billion years it took Earth to develop intelligent life–as to why we are still searching the skies for company.
The good news is that we may have overcome two of the three hardest barriers to becoming a galactic civilization—the advent of life and the advent of intelligence—and we only have one more to go—the advent of interstellar travel. Fortunately that’s the one that is (mostly) within our control and capacity, and I firmly believe we will get there eventually.
But I am inclined to think that this last barrier is not one that many species who reach it will fall at. Which leads me to think that while the galaxy may be is teeming with life, we won’t find much intelligence in amongst it.
Either that, or we are being held at arm’s (tentacle’s?) length as we continue to be observed from afar until we make that first step into interstellar space, because if there is other intelligent life out there, the odds are that they already know we’re here.
Even if intelligent life is rare, there is still hope for contact from further afield. While the technological issues may be orders of magnitude more difficult, an intelligent race had found no companionship within their home galaxy, might feel the need to reach out across the gulf between galaxies to find someone they can call friend.
Finally, if we do find that life is plentiful in the Milky Way, but we alone have evolved to sentience, what are the odds that we will be able to resist tinkering with life on other planets (perhaps after transporting to another barren world) in order to give it a nudge in the right direction? Then, in a few million years, we could have some new friends to play with!
Hey — perhaps that’s already happening…..
Fully agree with tacitus, very well said.
In addition, I wonder, with ref. to another recent thread and ensuing discussion (https://centauri-dreams.org/?p=8992#comments), to what extent the late arising of complex life may have been correllated with the much more ‘aggressive’ young sun (emitting vastly more dangerous radiation, particularly the harder types of UV). Complex life and in particular land-dwelling life may not have had a chance under those circumstances.
It is often mentiond, also in the above article, that the rise of complex life depended on the appearance of (abundant) oxygen in the atmosphere:
“Then just over half a billion years ago, (…), perhaps in part due to these ancient microbes giving off oxygen for ages, which brought about what scientists call the Cambrian Explosion or Radiation”.
However, this just seems to shift the problem to the question why those oxygen producing microbes appeared on the scene so late. Moreover, once you have them, the earth’s atmosphere could be filled with oxygen very quickly (probably on the order of a couple of hundred thousand years only).
Could it be that the real root cause of all this was the over-abundance of solar hard UV (also producing large amounts of ozone, O3, which is very nice at high altitudes, but not at low level)?
The last part of Tacitus’s post reminds me of Clarke’s 2001 series (I am presently reading 3001, after just having finished 2061; spending a lot of time on the train commuting). Yes, we and probably intelligence in general, longs for communicatin with other intelligence. However, since intelligence seems to be such a rare fluke, I wonder whether it is possible/predictable at all to tinker with life in order “give it a nudge in the right direction”.
Intelligence might very well leave living planets (particularly with complex life) alone and intact, apart from observation and study, to develop on their own, but the seeding of life on lifeless but terraformable worlds (“transporting to another barren world”) indeed seems a logical move and maybe even an irresistable temptation for an advanced civilization.
“As the late Cornell astronomer Carl Sagan once famously said: “We are made of star stuff.””
Or as Joni Mitchell said earlier and more melodiously, “We are stardust”.
tacitus – Apparently you do not know many creationists. That statement certainly does not give me fits. It is one reasonable interpretation of the scientific information that we have so far. Other than that I agree with Ronald that your post is ‘well said’.
Paul,
I’m afraid though that our distant descendants won’t have several
billion years to find another home. The Sun is slowly becoming brighter so that it is estimated that the Earth will become too hot for complex life in 0.5 to 1 billion years. Eventually it will resemble present day Venus.
Hi Folks;
I am duly impressed regarding the fine analytical and numerical models of exo-planetary dynamics that are being developed.
As some one trained in physics, as well as being a son of a deceased former U.S. Navy Officer who worked within the U.S. Navy’s Naval Reactors Division as a nuclear engineer, I have for many years focused most of my attention and interest regarding physics on the sub-atomic and sub-nuclear realm and plan to continue to do so. However, even though we can run advanced lattice QCD computations and gleam insight into the world at the level of quarks and gluons and the electroweak interaction, even the long term prediction of weather events of Earth as to it accuracy has defied our efforts.
We are now coming up with good climatological models for the environmental dangers we face with global warming and the like, and such super-computer intensive models and methods have made their way into exo-planetary dynamics and studies of the pathways in which life can emerge on other planets.
We are familiar with the notion of various eras, epochs, and phase changes within the current Big Bang paradigmatic models such as the three symmetry breaking events that lead to the decoupling of the 4 known forces, inflation, the photon-plasma decoupling at T ~ 3000 Kelvin and the like. Perhaps the emergence of sentient rational life is yet another phase change albeit a long duration one that for some deep reason, nature has preferred to undertake.
Regardless of whether sentient rational and affective self awareness is some principle all to its self, perhaps another dimension of mattergy, or is some emergent holistic phenomenon that is more than the sum of its parts, modern neuropsychology, neuropsychiatry, cognitive science and the like have irrevocably proven the extreme degree of coupling between conscious activity and neuro-physical substrates which are ultimately based on or comprised of quarks, gluons, leptons, photons, weak force bosons and the like.
The beauty we see in the development of planets which seems ubiquitous throughout our universe, and the development of any exo-biospheres is a process that can continue in ever greater richness and variety to the extent that new thermodynamic states can be achieved on such worlds, i.e, the set of possible thermodynamic state is not used up as to its uniqueness.
I guess the main point I am trying to make is that I am really enjoying these exo-planetary science threads. From someone who has also had a love for natural scenes such as shore side, lake side, and mountain top vantage points,. I like to point out when the subject comes up that the set of all such unique vantage points throughout just our universe or small but cosmically large portion thereof must be some sort of infinity scrapper in number.
If we don’t have the wherewithal to complete the colonizing other solar systems within 1/2 million years, then I doubt it will matter whether Earth has 1/2 billion or 5 billion years left.
Indeed, unless there is some calamitous world-changing event within the next 500 years, I fully expect we will have plenty of scouting missions well on the way to the stars by then, and 5,000 years from now we are likely to be activity colonizing other star systems (terraforming, if necessary).
Throw in a couple of collapses of civilizations before we get to that point and perhaps the day when human beings awake under an alien sun will be delayed a few thousand years, but in terms of the expected lifetime of life on Earth, that would be a mere blip.
I am not terribly optimistic about our chances of manned missions to other planets within my lifetime (another 35 years, touch wood), but given a few hundred years, I think humankind’s ingenuity will be successfully applied to the problems of space travel within and beyond the solar system.
I believe long before the required time we’ll be able to move the Earth and Mars outward and then inward again billions of years later. Maybe even Venus if we want to terraform it someday.
Here is one of the many sites that propose a similar method to first move the planets outward and then inward.
http://www.newscientist.com/article/dn14983-moving-the-earth-a-planetary-survival-guide.html
@tacitus:
”
Indeed, unless there is some calamitous world-changing event within the next 500 years, (…).
Throw in a couple of collapses of civilizations before we get to that point and perhaps the day when human beings awake under an alien sun will be delayed a few thousand years.
”
Maybe you are right, but I was thinking something else at the same time: perhaps a few serious but not all-out destructive (chance) events, or at least the realistic menace of those events, might wake up humankind to the seriousness of interstellar travel and settlement as a long-term goal, in order to preserve our civilization or even our species.
A new ice age, supervolcanic eruption, meteorite impact, pandemic, …
If humanity fails to colonize the stars and goes extinct, 0.5 to 1.0 billion years might just be enough for a second intelligent species to evolve and succeed where we fail. (Or, if we leave the earth and somehow abandon it, join us in space).
I suppose some bacteria-grade life could survive beyond the 1.0 billion year mark, but probably bacteria won’t be able to develop a space program. (Though they might still get to colonize other worlds by fortuitous meteor impacts ejecting them into space)
@forrest noble:
“I believe long before the required time we’ll be able to move the Earth and Mars outward and then inward again billions of years later.”
I would argue that if we get to the point where we have the technology to move the planets around, we wouldn’t actually need to.
I suspect the same logic applies to megastructures like Dyson spheres as well.
Besides at the present epoch there are plenty of other worlds out there. Interstellar travel seems far easier than moving planets around: bear in mind if you’re doing planet moving you have to prevent the system going haywire as you shuffle the various resonances around… heavy bombardments from destabilised asteroid belts would be bad, planet-planet scattering would be worse. (There’s an interesting, if somewhat implausible idea for a sci-fi story: eccentric exoplanets as examples of solar system engineering gone horribly wrong…)
Besides why go to all that effort to try to save a planet that will die thanks to the shutting down of various geological processes (plate tectonics, the geomagnetic field, etc.) anyway?
It was said: “Hopefully long before our Sun comes to the end of its life, our very distant descendants will have left Earth and the Solar System to start new lives in other parts of the galaxy.”
Hopefully this migration will occur sooner rather than later since there will be threats capable inducing human extinction on a timescale much less than the time it will take the Sun to evolve into a red giant. Asteroidal and cometary impacts immediately come to mind and fit this description.
Will governments ever come together and invest monumental resources (and half-hearted “faster, better, cheaper” efforts will surely not suffice) into ensuring that this migration takes place? Is there any sign that governments will undertake this project when in the coming decades humanity will be faced with several major issuess, such as: natural resource depletion, environmental degration, and climate change? Will they do what it takes to make it to the stars before it is too late? I hope so, but it may take special guilds or societies apart from governments who make it their end all and be all to bring about interstellar migration. I would quit my job in human services to join such a group tomorrow even if success was not likely in my lifetime. What could be more exciting than exploring the geology, let alone biology of endless numbers of worlds and being able to finally break away from failed isms and deadend zombie ideas that clearly aren’t working here on Earth? Who else is with me on this?
Hi spaceman;
Regarding your above rhetorical question,
“What could be more exciting than exploring the geology, let alone biology of endless numbers of worlds and being able to finally break away from failed isms and deadend zombie ideas that clearly aren’t working here on Earth?”
I could not agree with you more. The wide, perhaps unlimited variety of life forms in the cosmos, and the perhaps infinity scrapper varieties of physical life forms just within our universe based on the huge number of possible thermodynamic states afforded intelligent and rational organisms with a rest mass on the orders of 10 EXP -1.5 metric tons to 10 EXP – 0.5 metric tons is astounding at the very least, and at the very least, inspires me with a sense of reverential awe for the size, existentially and ontologically, dimensional extension wise, and elemental set wise, of just our universe alone, which may be but a dust spec in a vast ocean of created existence, which is likely infinity vast and ultimately incomprehensibly grand.
The number of unique possible personalities, unique personality profiles, psychodynamic traits and attributes such as abstract thinking ability, logical thinking ability, introspective intelligence including but not limited to auto-biographical memory, sexuality in its various forms (a topic that is of personal interest to me in many ways including from a scientific standpoint), emotional intelligence, social intelligence, volitional intelligence, athletic intelligence, intuitive and creative intelligence, and even the unique temperament profiles including instinctual and drive based psychodynamic traits, and any paranormal skills that any such ETI persons might have is potentially as limitless as the possibly perfectly continuous nature of the possible statistical variations in the make up of the psyches and personalities of human and any ETI persons.
I like to go hiking, for short hikes of course since I weigh quite literally about 1/4 of a ton and am thusly out of shape, in the Shenandoah National Park in Virginia which is about 60 miles from where I live. Every time I visit the park, I am elated at the beautiful mountain scenery and overlooks especially on a clear autumn day. The potentially innumerable unique vistas and geological formations against the backdrop of the essentially numberless unique star light spectrums or star shines that illuminate the day time scenes on such planets is the stuff of story book dreams as well as a potential reality for we humans as we venture out into the universe.
The point is, I am greatly inspired by your above post and could not agree with you more. As we squabble over the rather this or that politician should be impeached, or which Hollywood actor dissed who, or who will fund the Euro Missile defense systems, and a whole host of other trivial that mean nothing in the grand scheme of things, we are squandering our civilizations opportunity to do some thing really big and bold such as interstellar human space travel. The opportunities are far too big to miss out on.
“Besides why go to all that effort to try to save a planet that will die thanks to the shutting down of various geological processes (plate tectonics, the geomagnetic field, etc.) anyway?”
What’s the time frame for the persistence of geological processes on earth? I last heard it was in the order of 45-50 billion years, much longer than the lifespan of the sun.
This leads to the paradoxical possibility that life could survive longer on earth if earth got ejected from solar orbit (say by some close encounter with another star or other mechanism), since geothermal activity could still melt seawater around vents at the seafloor, providing a viable habitat even if the rest of the wandering planet froze solid.
Also, a sufficiently advanced technological civilization may not necessarily require a geologically active planet to survive. Most of the “services” provided by geo-activity could in theory be replicated by sufficiently advanced geo-engineering.
Depends on what level of geological activity you’re looking for. It may well take 50 billion years for the planet to cool stone dead, but geodynamic habitability models tend to predict the maximum habitable lifetime for an Earth mass planet as roughly 6-10 billion years (even when neglecting changes in stellar luminosity). Main problem is the growth of non-subductable continents which increases the rate of chemical weathering, which combined with lower levels of volcanic activity cause catastrophic fall in the level of carbon dioxide. Then it doesn’t matter where you put it, the habitable conditions become unstable.
Well, I heard many theories concerning the beginnings of the existence of our planet. One of them said that our Solar System was created by centrifugal forces, which were acting in a nebula. The scientist call it “the theory of the cigar”.
There is the theory head-on collision too. It says that the Earth and either planet had the head-on collision. As a one of results of this horrible event, the Moon was created.
It was a fact the poles on the Earth were changing their places in the past. The falls of huge celestial bodies in surface of our planet, such as planetoids and meteors, were a reason of this phenomenon. These uninvited visitors from outer space caused the changing angle of inclination of the Earth in relation to the Sun. As a result of this changing were the changes of the climate.
As for end of our planet, I always say: “We have to wait the five billions years and see”. I have a hope the humanity will be able to find the method necessary to survive. Even to rescue the Earth.
Chemistry of atmospheres formed during accretion of the Earth and other terrestrial planets
Authors: L. Schaefer, B. Fegley Jr.
(Submitted on 22 Sep 2009)
Abstract: We used chemical equilibrium and chemical kinetic calculations to model chemistry of the volatiles released by heating different types of carbonaceous, ordinary and enstatite chondritic material as a function of temperature and pressure.
Our results predict the composition of atmospheres formed by outgassing during accretion of the Earth and other terrestrial planets. Outgassing of CI and CM carbonaceous chondritic material produces H2O-rich (steam) atmospheres in agreement with the results of impact experiments. However, outgassing of other types of chondritic material produces atmospheres dominated by other gases.
Outgassing of ordinary (H, L, LL) and high iron enstatite (EH) chondritic material yields H2-rich atmospheres with CO and H2O being the second and third most abundant gases. Outgassing of low iron enstatite (EL) chondritic material gives a CO-rich atmosphere with H2, CO2, and H2O being the next most abundant gases. Outgassing of CV carbonaceous chondritic material gives a CO2-rich atmosphere with H2O being the second most abundant gas.
Our results predict that the atmospheres formed during accretion of the Earth and Mars were probably H2-rich unless the accreted material was dominantly CI and CM carbonaceous chondritic material. We also predict significant amounts of S, P, Cl, F, Na, and K in accretionary atmospheres at high temperatures (1500-2500 K).
Finally, our results may be useful for interpreting spectroscopic observations of accreting extrasolar terrestrial planets.
Comments: 41 pages, 1 table, 7 figures, submitted to Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:0909.4050v1 [astro-ph.EP]
Submission history
From: Laura Schaefer [view email]
[v1] Tue, 22 Sep 2009 17:29:27 GMT (158kb)
http://arxiv.org/abs/0909.4050
Ancient Ocean Oxygen Production Began 100 Million Years Earlier than Thought
http://www.spaceref.com/news/viewpr.html?pid=29531
“Scientists widely accept that around 2.4 billion years ago, Earth’s atmosphere underwent a dramatic change when oxygen levels rose sharply.”
According to the BBC, though, living stromatolites have just been found in a place frequented by bazillions of tourists—the Giant’s Causeway, a formation of basaltic hexagons in Northern Ireland:
In a small grey puddle tucked into a corner of the world famous Giant’s Causeway, scientists have made an extraordinary find.
A colony of stromatolites – tiny structures made by primitive blue-green algae.
Stromatolites are the oldest known fossils in the world.
The tiny algae or bacteria that build them are also thought to be the most ancient life form that is still around today, after more than three billion years.
What makes the discovery in Northern Ireland so remarkable is that until now these structures have been found mainly in warm and often hyper saline waters which discourage predators.
The stromatolites in the Giant’s Causeway are in a tiny brackish pool, exposed to the violence of waves and easy prey to the animals that are already living amongst them.
http://whyevolutionistrue.wordpress.com/2011/10/14/living-stromatolite-found-in-ireland/
The Origin of the Solar System
Authors: Michael Perryman
(Submitted on 5 Nov 2011)
Abstract: This article relates two topics of central importance in modern astronomy – the discovery some fifteen years ago of the first planets around other stars (exoplanets), and the centuries-old problem of understanding the origin of our own solar system, with its planets, planetary satellites, asteroids, and comets.
The surprising diversity of exoplanets, of which more than 500 have already been discovered, has required new models to explain their formation and evolution. In turn, these models explain, rather naturally, a number of important features of our own solar system, amongst them the masses and orbits of the terrestrial and gas giant planets, the presence and distribution of asteroids and comets, the origin and impact cratering of the Moon, and the existence of water on Earth.
Comments: 14 pages, 3 figures. Invited contribution to the European Review, the Interdisciplinary Journal of the Humanities and Sciences of the Academia Europaea
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1111.1286v1 [astro-ph.EP]
Submission history
From: Michael Perryman [view email]
[v1] Sat, 5 Nov 2011 08:11:47 GMT (500kb,D)
http://arxiv.org/abs/1111.1286