Enveloping Unvierse

October 4, 2011

Carl Sagan wrote that if the Earth were the size of a globe our atmosphere at that scale would be about as thin as a single sheet of paper. Yet the air we breathe is so fundamental to life that even the tiniest changes in the composition of our air could cause cascading climate change on a global scale. While carbon dioxide is present in only trace amounts, scientific consensus indicates at a change from 292 parts per million today to 380 parts per million by the next century could spell disaster for human civilization through rising sea levels, changes in established wind and ocean currents, melting ice caps and desertification associated with the overall average trend of global warming. And so atmospheric regulation is essential to the continuing survival of all life; this biogeochemical process is mainly controlled by single-celled organisms.

Our atmosphere on Earth is mostly made of nitrogen, but it’s also about 20% oxygen. Oxygen is a corrosive gas that is dangerous under high concentrations because of how reactive it is with other chemicals. But this concentration of oxygen has been by no means stable over the last four-and-a-half billion years; oxygen levels in our atmosphere have been virtually non-existent until about half a billion years ago, when the so-called Great Oxidiation Event (GOE) took place. The GOE released huge plume of oxygen into the sky over the course of a few million years, radically altering the compostition of life on Earth and giving rise to the ancestors of the eukaryotes. Early life on Earth was anaerobic, meaning that it could function without oxygen. While aerobic animal life takes in oxygen and burns it during metabolism to create carbon dioxide and energy as waste, anaerobic life uses a myriad of metabolic pathways to produce energy, reducing molten iron, acetate, sulfate, hydrogen gas, or other inorganic molecules to produce their energy.

It wasn’t until the rise of cyanobacteria that any appreciable oxygen could be produced. These cyanobacteria are blue-green algae that performed photosynthesis by taking in sunlight, carbon dioxide and water to grow. One byproduct of this reaction was oxygen gas. The early Earth environment was highly reducing, meaning that it would readily absorb any oxygen and quickly oxidize something in the environment. Substrate like iron (III) dissolved in the water would readily oxidize and become iron (II) oxide, which was insoluble in water and would sink to the bottom of primordial seas. We find these banded iron deposits around the world and they are a ready source of the iron we use in modern manufacturing. The presence of banded iron formations would indicate the presence of oxygen being produced by cyanobacteria at the time, so we can reasonable assume that aerobic photosynthesis was going on around 2.1 billion years ago. In fact, cyanobacteria were so pervasive on Earth that their combined exhalations of oxygen radically altered the composition of air.

Areios’s atmosphere is mostly nitrogen, like the Earth’s atmosphere, but the outgassing of volcanoes and the rapid destruction and creation of crust means that oxygen is less abundant in the atmosphere, which has profound implications for the development of animal life. Combine this with the later start for photosynthesis, and this means that aerobic life doesn’t appear until about 12 billion years into Areios’ existence, yet this kind of more complex life persists for over 3 billion years before the surface temperature gets too hot for photosynthesis to maintain itself permanently. Fifteen billion years after creation, the planet’s atmosphere undergoes another profound change. As Hemera gets brighter, the atmosphere would start to slump off and this would alleviate some of the heat that gets trapped in the Areiosan atmosphere. Eventually the atmosphere becomes so thin with carbon dioxide that there isn’t enough CO2 to fuel photosynthesis and plants would die off en-masse. This drop in carbon dioxide would eliminate the greenhouse effect on Areios, and in turn this massive die-off would incite the next ratcheting up of carbon dioxide, which would in turn lead to a positive temperature feedback loop. Oceans would boil over until the last life left on the planet would paradoxically resemble the earliest life; a halophilic thermophile. Eventually, even this hardy creature wouldn’t be able to survive Areios would once again be a world sterile of all life. Temperature would still rise, though, and would boil the carbon dioxide out of the carbonate rocks in the crust, causing a runaway greenhouse effect like the one that we see on Venus. Sadly, this is the fate of all terrestrial planets as their parent star grows old; the same fate awaits our own planet earth in the coming eons.

Long after the Earth's atmosphere boils away, our Sun will evolve into a Red giant star.

Eurytopic Universe

August 2, 2011

Temperatures are on the whole lower on Areios and combined with lower levels of oxygen means that all organisms on Areios are limited by these conditions. The aliens we find on this world are not towering monsters; Areiosans are tiny by comparison to their Terroan cousins. The largest animals on Earth are creatures like sequoias or blue whales, but Areiosans pale in comparison to this. The largest Areiosans are about the size of a horse. Clonal colony organisms like honey mushrooms and coral reefs however, are a different story. On Earth, aspen trees are a conglomerate of root systems that some ecologists argue could be construed as a single organism. Areiosans have much more surface area to sprawl out, more wide open spaces to colonize. The immense gravity keeps them down though. One wouldn’t find anything resembling a giraffe on Areios; most creatures heed gravitropism on Areios, growing outward not upward. Fungi cover huge swaths of Areiosan continents, filling up niches usually afforded to moss or lichens on Earth. And the oceans are just as teeming with life; purple and red algae blanket the surface of oceans, tinting the seas blood-red. These algae colonies are the lifeblood to all animal life because they serve as the organisms on the planet to replenish oxygen by virtue of the dearth of plant life on Areios. Their origin paves the way for animal life to evolve later on.

The first algae don’t appear on Areios until there is enough sunlight penetrating the lower atmosphere to support photosynthesis. The smog of the Areiosan atmosphere blocks most of Hemera’s light from breaking through, but as the star brightens, it begins to overcome the hazy atmosphere and penetrate to the surface of the planet. The first algae descended from aquatic organisms floating on the surface of oceans, eating the iron dissolved in the water. When the faint slivers of ultraviolet light broke through the atmosphere, it would cause die-offs of the surface protists. A mutation in a gene that coded for a membrane protein changed the function of a surface protein, allowing it to transmit and reflect light instead of absorbing it, acting like a sunscreen. Channeling those ultraviolet photons outside of the cell, this novel protein is of benefit to these protists because they no longer risk exposure to dangerous ultraviolet rays. This rudimentary sunscreen is the first step towards building photosynthesis on Areios.

Plants on Earth are fine-tuned to utilize the light coming from the Sun, which means that plants transmit mostly red and yellow light while green light bounces off the pigments and into our eyes, which is why we plants as green. But these colors are only specific to plants on Earth, which are calibrated to maximize the amount of energy they can extract from the light from our Sun. But on another planet, a different Sun would put out a different range of the visible light spectrum more than our Sun and this would mean that plants on those planets would reflect a different color on the spectrum and we could see plants that range from jet-black to silvery-white and any color in between. On Areios, there are no plants because sulfur dioxide withers cellulose and burns the chlorophyll pigments plants use. While algae possess a unique bacterial form of chlorophyll, they are not true plants. The only way to run photosynthesis on Areios is within the insulating environment of the ocean. Photosynthetic algae on Areios have to rely on the dim light from Hemera, so photosynthesis on this planet relies on yellow and green light, so instead algae have a dark blue-violet color to help their pigments absorb light.

Over time, mutations accumulated in this population that led to the appearance of very basic mechanism for electrons to pick up the photons that strike its surface. With successive generations cells evolved more efficient ways to pick up photons and ferry them outside the cell. Somehow in piecemeal additions to the mechanisms of these cells, the photons that once were an occupational hazard for these surface-dwelling protists became a source of fuel for future populations; these photons got gobbled up by electrons and passed like a game of hot-potato through the cell membrane of these protists. Those electrons became a currency for a metaphorical toll booth that allowed protons passage out of the cell. These protons carry a positive charge and there is a charge gradient when you compare the inside of the cell with the outside of cell. But protons would not ordinarily want to move outside of the cell, and so special proteins embedded within the cell have to facilitate the movement of protons outside of the cell. This movement of protons across the cell membrane of a protist is called the proton motive force that fuels ATP synthesis.

On our world, plants appear green, but not this need not be the case; planets orbiting different stars could host different-colored plant life

Empyreal Universe

July 5, 2011

ATP synthase is an enzyme embedded at the end of the electron transport chain that creates ATP. Protons from outside the cell pass through the ATP synthase enzyme into the cell. This energy drives the ATP synthase to string phosphates onto a molecule of adenosine and create ATP. Areiosan cells function remarkably in the same way, except ATP synthase strings molecules of arsenate to a molecule of mercapto-adenosine, which is an analogue of adenosine that features sulfur built into the structure. It’s remarkable how analogous our biochemistry is with Areiosan life. Despite a different set of chemicals, the reactions inside our cells seem to mirror those on Areios. Our biochemistry is so analogous that it is reasonably clear to suggest that life adheres to a specific set of chemical pathways and even from one world to another, the same kinds of chemical reactions are preserved, albeit with slight changes in the chemical reagents used.

 
All life uses an electron transport chain to shuttle electrons through their cell membrane, powering pumps to make their fuel source, the molecule called adenosine troposphere (ATP). The electron transport chain for an organisms that can undergo photosynthesis begins when a discrete packet of light called a photon gets passed around through a cell‘s machinery. First of all, light can behave as a particle called a photon. Photons can come in different ‘colors’ that correspond to the wavelength of that photon. The visible light spectrum ranges from blue-violet on one end of the spectrum, and red on the other end of the spectrum. Blue light has the shortest wavelength of visible light while red light has the longest wavelength. Wavelength corresponds with how many times a wave of light cycles from start to finish. Each wave can be thought of a single photon, so blue light has more energy per unit length because a shorter wavelength means more waves per unit length and therefore more energy and photons are available.  

 
Photosynthetic organisms on Earth rely on mainly red and yellow light to power photosynthesis, but this need not be the case. Scientists proffer that plants could use light as far from the lower end of the infrared spectrum to the upper end of the ultraviolet spectrum. The output of the parent star determines the color that a plant will utilize; red and yellow light are the most abundant wavelength of photon emitted from our Sun, so the vast majority of organisms utilize that most abundant source of energy rather than blue or green, which is not as available. But Areios’ star Hemera is characteristically dimmer than our Sun, so it shines with an orange-red glow. For algae on Areios, they tend to absorb more green and yellow and reflect blue and violet light. Because there is no plant life on Areios, redish and purple algae are among the few photosynthesizing organisms on the planet and the ocean surfaces are covered in it, giving much of the world a blood red or violet hue. These algae are amongst the oldest photosynthetic life forms on Areios, and while they cannot undergo photosynthesis or produce oxygen, they play a major role in most ocean ecosystems; because they can tolerate high concentrations of salts in Areios’ briny seas, they are the basis for several aquatic food webs. Some of these purple algae don’t rely on chlorophyll at all, but use a pigment similar to rhodopsin, like the coloring found in human retinas, to absorb light and power their ATP synthesis.
But every photosynthetic creature faces a limitation on how far down the visible spectrum they can utilize. Called the red edge, plants on Earth avoid absorbing light coming from the infrared end of the spectrum because they have to protect themselves from overheating. This isn’t as big of a problem for Areioan life because Areios is on the whole colder than Earth in terms of average temperatures.

Infrared red light is essentially what we perceive as heat and while algae on Areios can absorb infrared light, they too meet a limit on much they tolerate. Their red edge is around infrared wavelengths of 1.5 μm or so, but there are other organisms on Areios that can tolerate much greater into the infrared. Some creatures can see well into the infrared rage enough that their eyesight does not depend on any visible light. Their eyesight would be nearly identical to the infrared telescopes that are used to study astronomical bodies. Perhaps the most astonishing impact of this is that some creatures on Areios would be able to see the universe from a totally different perspective than humans; their infrared vision could view the oldest objects in the universe unaided by a telescope or observatory like we humans must use. Perhaps most amazing of all is that these creatures can do so without the need for cryogenic coolants. Our earth-borne telescopes need to be cooled down to near-absolute temperatures to work in the far infrared spectrum, but Areiosans are not encumbered by that limitation at all. Outside their murky atmosphere lies an exotic universe that they can see with their own eyes. Or eye.

 

This photo of the milky way galaxy shows a different view of our galaxy when viewed in the infrared. This is how our universe looks from view of Areiosan life.

Eavesdropping Universe

June 30, 2011

The Search for Extraterrestrial Intelligence (SETI) is on the brink of discovering habitable worlds in our own galaxy. With probes like the Kepler telescope already searching the stars in our galaxy and the Terrestrial Planet Finder probe soon to be launched, we have begun the search for worlds that resemble for own. While the thought of ever visiting these alien planets is still a fantasy, science fiction writers are already speculating on what we might find on these planets. Check out these links to discover more about the search for habitable worlds, the science beyond science fiction, and one curious collaboration between science and music that is truly out of this world.

 

Edge of the Universe

June 11, 2011

Check out this latest press release from the  NASA Science News webpage; the Voyager probes are beaming back some very interesting information on what its like at the far reaches of our own solar system.

 

Encompassing Universe

March 8, 2011

The Earth’s crust is made mostly out of oxygen and silicon, but that need not be the case for terrestrial planets. Terrestrial planets can be iron-rich, carbon-rich, water-rich, or silicate-rich. As terrestrial Earth-type planets go, any planet with a significant amount of mass will accumulate an atmosphere, but if the planet gets too massive, it will take on too much atmosphere and become a gas giant more akin to Neptune or Uranus. If a planet is too small, it won’t accumulate much of an atmosphere at all and that will prevent liquid water from accumulating on the surface making the surface of the planet dry and frozen like Mars. A smaller planet will have its liquid outer core and mantle solidify faster, so volcanism and the planet’s magnetic field will shut down much quicker than on Earth. With no volcanism to replenish the atmosphere, no magnetic field to keep solar wind at bay, and a generally smaller gravitational field that can’t hold on to as much atmosphere, smaller planets are less habitable than Earth-mass planets and greater and aren’t habitable for as long, either.

A terrestrial planet more massive than Earth but less than about 10 times the mass of the Earth is considered a super earth. Anything more than 13 times the mass of the Earth would cause the planet’s gravity to hold on to too much gas and the thick envelope of a gas giant’s atmosphere would form. One astronomer suggested that a gas giant could be stripped of its atmosphere and may became a chthonian planet if a nearby massive star goes nova and tears the atmosphere off the planet, which you would expect to find in a galactic area with high-metallicity and many nearby aging stars. Super earths can be classified by their composition and internal structure and they come in two major varieties; water-rich and rocky super earths.

Iron-rich planets would form closer to the protoplanetary disk of the star they orbit, where metal content is highest. Planets rich in iron would cool quicker than silicate-based planets and that means volcanism, plate tectonics and a magnetic field would halt much sooner on a planet that cools that quickly. Mercury in our solar system is most similar to this; Mercury’s lighter silicate crust could have been boiled away, leaving behind the iron core, which makes up a greater proportion of the planet’s mass.

Our Sun has a carbon: oxygen ratio of about 0.5, so CO2 is common in the atmosphere of planets with silicate crusts. Bur for super earths that would accumulate much more carbon than a planet like Earth, there would be less CO2 in the atmosphere and the crust would be made predominantly of silicon carbide and graphite, and a layer of diamonds would be present deeper within the crust as graphite gets squeezed by heat and pressure to form diamonds. During volcanic eruptions, molten diamonds would gush from the volcano along with silicon carbide.

Planets covered by ocean are called water worlds, and because of the pressure of the atmosphere, this water would form a layer of ice VII over the entire surface of the planet. Ice VII is a truly alien form of water that would be crushed into a solid form at near-boiling temperatures. Water worlds resemble planets like Uranus or Neptune that would have migrated closer to their star and melted. These planets would be composed of a volatile content identical to the ice-bearing comets where their water would have come from. Rocky-type super earths might have the amount of water comparable to what one might find on Earth, but because the planet has a much bigger radius, oceans would straddle less of the planet’s surface, like it does on Areios. In fact, the amount of volatile content like water that gets captured by a planet might vary on an order of magnitude of about 1,000. This means that a planet could wind up with next to no water on its surface, or it might be flooded with water all over its surface. While a water world may be habitable to life, space faring intelligent life can’t arise on a water world because if a species can’t even build fire, these creatures certainly couldn’t discover rocketry, radio telescopes or even metallurgy. This means that unless we build a rocket and fly to one of these water worlds, we may never come in contact with an intelligence that dwells there.

A silicate-rich planet would resemble the terrestrial planets in our solar system; the crust would be made of silicon dioxide mostly, and plate tectonics would control the amount of carbon dioxide in the atmosphere by virtue of subduction. Areios is a silicate-rich planet like our Earth, but because of its more massive size, volcanism wipes the atmosphere clean of carbon dioxide just as fast as volcanoes can spurt it out. The same volcanic processes on Earth appear on Areios, but at a much faster pace. The crust on Areios is the same thickness as on earth, yet with a larger mantle and more gravity pushing down on the crust; plate tectonics operate in the same mechanism as they would on Earth, with the denser basalt plates getting driven beneath the lighter continental crust.

Enterprising Universe

March 5, 2011

Richard Hoover of NASA’s Marshall Space Flight Center reported in the March Issue of the Journey of Cosmology that he had discovered evidence of microfossils in carbonaceous chrondites that fell to the Earth. Hoover’s research suggests that these fossils are not Earthly contamination, but evidence of life that lived on another body in the solar system. Fragments of their original environment traveled through space until these most primitive meteorites arrived to the Earth via meteorite impact. Here is a link to Hoover’s recently published article “Fossils of Cyanobacteria in CI1 Carbaceous Meteorites: Implications to Life On Comets, Europa, and Enceladus”. As reported by the Journal of Cosmology, “Members of the scientific community were invited to analyze the results and to write critical commentaries or to speculate about the implications. These comments will be posted on March 7 through March 10 2011.”

Expect more posts next week on any major developments surrounding Dr. Hoover’s recent discovery.

Electric Universe

March 1, 2011

In the very center of Areios is the core, a dense ball of iron and nickel that sloshes around inside the planet, generating a magnetic field like the one on Earth. The core is divided into an inner and outer layer, based on density and these two layers spin at different rates, causing a magnetic field to form from an induced dipole moment. The magnetic field on Earth is generated by the molten iron and nickel that gets swirled around by the tug of the Earth’s orbit. The magnetic field was actually induced by the magnetic field generated from the Sun, and kept going by the motion of the liquid iron outer core which can conduct electricity as it was churned by the Coriolis Effect.Magnetic Pole reversal

Because Areios will take longer to cool, its core won’t differentiate into inner and outer layers until much later in time relative to how it happened on Earth. Because the core won’t differentiate at first, there won’t be a magnetic field on Areios until the planet’s insides settle down. This is important because that magnetic field keeps solar wind from stripping the atmosphere away and it keeps out deadly radiation that would attack the organic machinery of cells. In the book The Life and Death of Planet Earth, Peter Ward describes what some astrobiologists believe happened to Venus and Mars when the magnetic field of a planet stops; solar wind tears water into hydrogen and oxygen, boiling away the atmosphere until the atmospheric pressure prevents water from collecting on the surface at any temperature. The result: a dry and frozen world like Mars, or a dry and broiling world like Venus. Because Areios won’t develop a magnetic field until later on, life probably couldn’t start until the radiation bombarding the planet could be deflected. Thankfully, Areios regenerates its atmosphere through volcanic venting and it has enough gravity to hold on to some of the gases that would otherwise leak out of an Earth’s sized planet’s atmosphere, so the atmospheric stripping one would expect from Hemera’s solar wind can be kept at bay, or at least mitigated for a while.

This magnetic field reverses from time to time, and we have evidence of this on earth in iron-bearing minerals that have spewed out onto the crust from the mantle. In the Atlantic Ocean, there are areas where new crust is being created; magma from the mantle forces its way onto the surface as lava that cools and forms the ocean floor. As it solidifies, new material pushes the old material out of the way as more lava wells up from the mantle in a process called seafloor spreading. Magnetized iron in mineral crystals from the mantle record which way the magnetic field is spinning at the time when it hardens into rock. These rocks record a trend of increasing or diminishing magnetization of iron in the mantle and they show evidence that over geologic time, the poles will reverse with the North Pole flipping down to the South Pole and vice versa. During the process where the magnetization flips, there are periods of weak magnetization that can be disastrous for life because this causes more ionizing radiation to leak through the atmosphere.

On Areios, the thicker mantle keeps the insides of the planet too hot to differentiate the mantle and core into two distinct layers until later on in Areios’ history. That means that for the earliest period in Hemera’s stellar life cycle, Areios is unprotected by the cosmic rays that Hemera would bring onto Areios’ surface. Only after Hemera stops blasting the surface of Areios with radiation does Areios develop a magnetic field. Four billion years after the formation of Areios, we see a number of habitability factors line up for the first time; Hemera stops having such violent solar flares, the bulk structure of the planet settles down to trigger its magnetic field, the planet’s volcanism shoot out less gas, which causes a geologic ice age period. All of these converging factors lead to the first Areiosan lifeforms, the Areia.

magnetic field

Click here for an animation of the Earth’s magnetic pole reversal by the Pittsburgh Supercomputing Center

Exciting Universe

February 20, 2011

Check out this link from MSNBC’s Cosmic Log: scientists point to Kepler’s potential discovery of what could be the most Earth-like exoplanets ever observed to date.

Enshrouding Universe

February 15, 2011

The Earth’s rotation has a profound impact on the environment. The friction of the moon’s orbit has been slowing down the rotation of the Earth very slowly over the last four billion years, and this has had a mediating effect on the velocity of atmospheric currents. Not only does the speed of our rotation influence the severity of our weather, but for Areios, the three small moons have less of a drag on the planet’s rotation, so Areios would rotate faster than Earth and has more intense weather patterns associated with a more vigorously churning atmosphere. The Coriolis Effect deflects the motion of our atmospheric currents, causing air currents to deflect towards the east in the Northern hemisphere and to the west in the southern hemisphere. While wind is generated by heating, it’s the Coriolis Effect that creates the prevailing winds we see at different latitudes. The weather on Areios has a more pronounced Coriolis Effect and because Areios rotates in a clockwise direction when seen from above (while the Earth rotates in a counter-clockwise direction), Areios would see winds deflected to the left in the Northern hemisphere instead of to the right like on Earth. Areios has a 256-day year as it revolves around Hemera and a 16 hour day that whips the atmosphere around creating monstrous storms over the planet. Most importantly, this vigorous atmosphere mixes the air currents so that the temperature on the planet is averaged out a bit more. Especially because Areios rotates on its side, the heat distribution around the planet can be at either extreme during winter and summer, where one side of planet is in darkness for weeks on end and the other side is scorched in perpetual sunlight for weeks on end. This would create a tremendous amount of evaporation, fueling intense hurricane activity where one side of the planet is experiencing summer.

During the summer months, Areios is at aphelion with Hemera, meaning that the planet is at its farthest approach from the star and during the winter months, the planet is at perihelion, or its closest approach to Hemera. The planet’s tilt determines the weather most significantly. The Earth’s atmosphere is made up of five distinct layers, much like on Areios. The layer of the atmosphere closest to the surface is called troposphere; this is where most of the atmosphere is contained and where all life and weather takes place within. As the altitude increases, we reach a point where the troposphere’s composition changes and makes way for the stratosphere. The stratosphere is where our ozone layer is located, which is important for keeping UV radiation from leaking into our atmosphere and causing higher incidents of cancer. Above the stratosphere is the mesosphere, where most asteroids will burn up upon reentry. And the outermost layer of the thermosphere contains the ionosphere where radio waves arriving from the surface get bounced off ionized particles in this layer and reverberated back down to Earth. Now beyond this ionosphere is the exosphere where the earth’s gravity effective gives away to outer space and the atmosphere stops. Unlike early Areios, the Earth has a magnetosphere that traps dangerous particles put off by the Sun; the magnetic field is generated by the rotation of the planet’s inner and outer core, which is influenced by the presence of our Sun, and its own magnetism and spinning core. Areios does not have this phenomenon at first because its hotter interior doesn’t form two distinct layers in the core until billions of years after its formation. Once the interior cools though, disparate motions of two distinct layers in the core will produce a magnetic field for Areios, which will help to prevent Hemera’s radiation from stripping away the atmosphere and bombarding the surface of the planet with ionized particles.

The early Areiosan troposphere is thick with smog; frequent lightning brought on by vigorous storms whip the atmosphere into a soup of chemicals that blocks out some of Hemera’s already dim light. While high levels of sulfur dioxide scatter the incoming solar radiation, carbon dioxide and water vapor spewed from volcanic eruptions trap what little heat is created and keep the oceans from frosting over. Areios’ greater mass means that it will retain lighter gases like hydrogen and helium, which escaped the Earth’s atmosphere early in the planet’s formation. This hydrogen becomes an important foodstuff for early life and contributes to the reducing environment of early Areios that makes the planet viable for the creation of life. As Hemera ages, it will warm up the cold planet, but until then, the atmosphere’s greenhouse effect suffices to keep Areios from becoming an ice world. The stratosphere is the most distinctly different; with no ozone layer to protect Areiosan life from UV radiation, the surface of the planet is still a dangerous place even with a hazy atmosphere obscuring light. The first life on Areios lives in the ocean before photosynthesis produces the oxygen that will make an ozone layer.

The Earth's magnetosphere deflects our Sun's solar wind, preventing charged particles from reaching the surface.