Even if Exoplanets Have Atmospheres With Oxygen, it Doesn’t Mean There’s Life There

In their efforts to find evidence of life beyond our Solar System, scientists are forced to take what is known as the “low-hanging fruit” approach. Basically, this comes down to determining if planets could be “potentially habitable” based on whether or not they would be warm enough to have liquid water on their surfaces and dense atmospheres with enough oxygen.

This is a consequence of the fact that existing methods for examining distant planets are largely indirect and that Earth is only one planet we know of that is capable of supporting life. But what if planets that have plenty of oxygen are not guaranteed to produce life? According to a new study by a team from Johns Hopkins University, this may very well be the case.

Continue reading “Even if Exoplanets Have Atmospheres With Oxygen, it Doesn’t Mean There’s Life There”

There Might be Enough Oxygen Below the Surface of Mars to Support Life

The possibility that life could exist on Mars has captured the imagination of researchers, scientists and writers for over a century. Ever since Giovanni Schiaparelli (and later, Percival Lowell) spotted what they believed were “Martian Canals” in the 19th century, humans have dreamed of one day sending emissaries to the Red Planet in the hopes of finding a civilization and meeting the native Martians.

While the Mariner and Viking programs of the 1960s and 70s shattered the notion of a Martian civilization, multiple lines of evidence have since emerged that indicate how life could have once existed on Mars. Thanks to a new study, which indicates that Mars may have enough oxygen gas locked away beneath its surface to support aerobic organisms, the theory that life could still exist there has been given another boost.

Continue reading “There Might be Enough Oxygen Below the Surface of Mars to Support Life”

Weekly Space Hangout – February 3, 2017: Meredith Rawls & the LSST

Host: Fraser Cain (@fcain)

Special Guest: Meredith Rawls

Meredith is a Postdoctoral Researcher in the Department of Astronomy at the University of Washington. She writes software to prepare for the coming onslaught of data from the Large Synoptic Survey Telescope and studies weird binary stars. She is also the lead organizer of the ComSciCon-Pacific Northwest workshop for STEM graduate students in Seattle this March. Meredith holds degrees in physics and astronomy from Harvey Mudd College, San Diego State University, and New Mexico State University. When she’s not science-ing or telling people all about it, she plays viola, volunteers at summer camp, and advocates for more equity and less light pollution.


Paul M. Sutter (pmsutter.com / @PaulMattSutter)
Kimberly Cartier ( KimberlyCartier.org / @AstroKimCartier )

Their stories this week:
Oxygen on the moon

Nearby “super-void” shapes galaxy motion

First science from Keck’s vortex coronograph

We use a tool called Trello to submit and vote on stories we would like to see covered each week, and then Fraser will be selecting the stories from there. Here is the link to the Trello WSH page (http://bit.ly/WSHVote), which you can see without logging in. If you’d like to vote, just create a login and help us decide what to cover!

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

If you would like to sign up for the AstronomyCast Solar Eclipse Escape, where you can meet Fraser and Pamela, plus WSH Crew and other fans, visit our site linked above and sign up!

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Universe Today, or the Universe Today YouTube page

Winged Telescope Detects Martian Atomic Oxygen

SOFIA in flight, with its telescope exposed. Image: NASA/Jim Ross

Finding atomic oxygen in the Martian atmosphere is very difficult to do, which explains why it’s been 40 years since it was last detected. In the 1970’s, NASA’s Viking and Mariner missions detected Martian atmospheric oxygen, and now, the Stratospheric Observatory for Infrared Astronomy (SOFIA) has detected atomic oxygen in the upper portion of the Martian atmosphere called the mesosphere.

SOFIA is a specially modified Boeing 747 aircraft which carries a 100 inch telescope. It flies at altitudes between 37,000 to 45,000 feet, which puts it above most of the moisture in Earth’s atmosphere. This moisture would otherwise block the infrared radiation that SOFIA “sees.”

“Atomic oxygen in the Martian atmosphere is notoriously difficult to measure,” said Pamela Marcum, SOFIA project scientist. “To observe the far-infrared wavelengths needed to detect atomic oxygen, researchers must be above the majority of Earth’s atmosphere and use highly sensitive instruments, in this case a spectrometer. SOFIA provides both capabilities.”

A close-up of SOFIA's telescope and primary mirror. Image: NASA/Tom Tschida
A close-up of SOFIA’s telescope and primary mirror. Image: NASA/Tom Tschida

A special detector on board SOFIA, the German Receiver for Astronomy at Terahertz Frequencies (GREAT) allowed researchers to distinguish Martian atmospheric oxygen from Earthly oxygen. SOFIA-GREAT only detected half the amount of oxygen that scientists expected to find, which is probably due to changes and variations in the atmosphere. These results were published in a 2015 paper in Astronomy and Astrophysics.

Atomic oxygen has a strong effect on Mars’ atmosphere because it affects how other gases escape the atmosphere. It’s extreme volatility means it bonds with nearby molecules very easily; oxygen will combine with almost all chemical elements, except for the noble gases.

SOFIA is the largest airborne observatory in the world, and is a joint project between NASA and the German Aerospace Center. SOFIA has a 20 year mission timeline. Researchers will continue using SOFIA to study the Martian atmosphere, in order to better understand the variations in oxygen content.

SOFIA is not the only mission with eyes on Mars’ atmosphere. NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) was launched in 2013 to explore the upper atmosphere of Mars, and how it’s affected by the solar wind. It’s thought that Mars’ atmosphere was much thicker in the past, and has been stripped away over time. Atomic oxygen played a role in Mars’ escaping atmosphere in the past, and no doubt will play a role in the future. SOFIA and other missions like MAVEN will hopefully shed some light on Mars’ past and future atmospheres.

How Do We Terraform Saturn’s Moons?

Continuing with our “Definitive Guide to Terraforming“, Universe Today is happy to present our guide to terraforming Saturn’s Moons. Beyond the inner Solar System and the Jovian Moons, Saturn has numerous satellites that could be transformed. But should they be?

Around the distant gas giant Saturn lies a system of rings and moons that is unrivaled in terms of beauty. Within this system, there is also enough resources that if humanity were to harness them – i.e. if the issues of transport and infrastructure could be addressed – we would be living in an age a post-scarcity. But on top of that, many of these moons might even be suited to terraforming, where they would be transformed to accommodate human settlers.

As with the case for terraforming Jupiter’s moons, or the terrestrial planets of Mars and Venus, doing so presents many advantages and challenges. At the same time, it presents many moral and ethical dilemmas. And between all of that, terraforming Saturn’s moons would require a massive commitment in time, energy and resources, not to mention reliance on some advanced technologies (some of which haven’t been invented yet).

Continue reading “How Do We Terraform Saturn’s Moons?”

Why Do Red Giants Expand?

We know that the Sun will last another 5 billion years and then expand us a red giant. What will actually make this process happen?

One of the handy things about the Universe, apart from the fact that it exists, is that it lets us see crazy different configurations of everything, including planets, stars and galaxies.

We see stars like our Sun and dramatically unlike our Sun. Tiny, cool red dwarf stars with a fraction of the mass of our own, sipping away at their hydrogen juice boxes for billions and even trillions of years. Stars with way more mass than our own, blasting out enormous amounts of radiation, only lasting a few million years before they detonate as supernovae.

There are ones younger than the Sun; just now clearing out the gas and dust in their solar nebula with intense ultraviolet radiation. Stars much older than ours, bloated up into enormous sizes, nearing the end of their lives before they fade into their golden years as white dwarfs.

The Sun is a main sequence star, converting hydrogen into helium at its core, like it’s been doing for more than 4.5 billion years, and will continue to do so for another 5 or so. At the end of its life, it’s going to bloat up as a red giant, so large that it consumes Mercury and Venus, and maybe even Earth.

What’s the process going on inside the Sun that makes this happen? Let’s peel away the Sun and take a look at the core. After we’re done screaming about the burning burning hands, we’ll see that the Sun is this enormous sphere of hydrogen and helium, 1.4 million kilometers across, the actual business of fusion is happening down in the core, a region that’s a delicious bubblegum center a tiny 280,000 kilometers across.

The core is less than one percent of the entire volume, but because the density of hydrogen in the chewy center is 150 times more than liquid water, it accounts for a freakishly huge 35% of its mass.

It’s thanks to the mass of the entire star, 2 x 10^30 kg, bearing down on the core thanks to gravity. Down here in the core, temperatures are more than 15 million degrees Celsius. It’s the perfect spot for nuclear fusion picnic.

There are a few paths fusion can take, but the main one is where hydrogen atoms are mushed into helium. This process releases enough gamma radiation to make you a planet full of Hulks.

Proton-proton fusion in a sun-like star. Credit: Borb
Proton-proton fusion in a sun-like star. Credit: Borb

While the Sun has been performing hydrogen fusion, all this helium has been piling up at its core, like nuclear waste. Terrifyingly, it’s still fuel, but our little Sun just doesn’t have the temperature or pressure at its core to be able to use it.

Eventually, the fusion at the core of the Sun shuts down, choked off by all this helium and in a last gasp of high pitched mickey mouse voice terror the helium core begins to contract and heat up. At this point, an amazing thing happens. It’s now hot enough for a layer of hydrogen just around the core to heat up and begin fusion again. The Sun now gets a second chance at life.

As this outer layer contains a bigger volume than the original core of the Sun, it heats up significantly, releasing far more energy. This increase in light pressure from the core pushes much harder against gravity, and expands the volume of the Sun.

Even this isn’t the end of the star’s life. Dammit, Harkness, just stay down. Helium continues to build up, and even this extra shell around the core isn’t hot and dense enough to support fusion. So the core dies again. The star begins to contract, the gravitational energy heats up again, allowing another shell of hydrogen to have the pressure and temperature for fusion, and then we’re back in business!

Red giant. Credit:NASA/ Walt Feimer
Red giant. Credit:NASA/ Walt Feimer

Our Sun will likely go through this process multiple times, each phase taking a few years to complete as it expands and contracts, heats and cools. Our Sun becomes a variable star.

Eventually, we run out of usable hydrogen, but fortunately, it’s able to switch over to using helium as fuel, generating carbon and oxygen as byproducts. This doesn’t last long, and when it’s gone, the Sun gets swollen to hundreds of times its size, releasing thousands of times more energy.

This is when the Sun becomes that familiar red giant, gobbling up the tasty planets, including, quite possibly the Earth.The remaining atmosphere puffs out from the Sun, and drifts off into space creating a beautiful planetary nebula that future alien astronomers will enjoy for thousands of years. What’s left is a carbon oxygen core, a white dwarf.

The Sun is completely out of tricks to make fusion happen any more, and it’ll now cool down to the background temperature of the Universe. Our Sun will die in a dramatic way, billions of years from now when it bloats up 500 times its original volume.

What do you think future alien astronomers will call the planetary nebula left behind by the Sun? Give it a name in the comments below.

Can You Kill a Star With Iron?

Since the energy required to fuse iron is more than the energy that you get from doing it, could you use iron to kill a star like our sun?

A fan favorite was How Much Water Would it Take to Extinguish the Sun? Go ahead and watch it now if you like. Or… if you don’t have time to watch me set up the science, deliver a bunch of hilarious zingers and obscure sci-fi references, here’s the short version:

The Sun is not on fire, it’s a fusion reaction. Hydrogen mashes up to produce helium and energy. Lots and lots of energy. Water is mostly hydrogen, adding water would give more fuel and make it burn hotter. But some of you clever viewers proposed another way to kill the Sun. Kill it with iron!

Iron? That seems pretty specific. Why iron and not something else, like butter, donuts, or sitting on the couch playing video games – all the things working to kill me? Is iron poison to stars? An iron bar? Possibly iron bullets? Iron punches? Possibly from fashioning a suit and attacking it as some kind of Iron Man?

Time for some stellar physics. Stars are massive balls of plasma. Mostly hydrogen and helium, and leftover salad from the Big Bang. Mass holds them together in a sphere, creating temperatures and pressures at their cores, where atoms of hydrogen are crushed together into helium, releasing energy. This energy, in the form of photons pushes outward. As they escape the star, this counteracts the force of gravity trying to pull it inward.

Over the course of billions of years, the star uses up the reserves of hydrogen, building up helium. If it’s massive enough, it will switch to helium when the hydrogen is gone. Then it can switch to oxygen, and then silicon, and all the way up the periodic table of elements.

The most massive stars in the Universe, the ones with at least 8 times the mass of the Sun, have enough temperature and pressure that they can fuse elements all the way up to iron, the 26th element on the Periodic Table. At that point, the energy required to fuse iron is more than the energy that you get from fusing iron, no matter how massive a star you are.

Massive Young Stellar Object HD200775 within the reflection nebula NGC7023.
Massive Young Stellar Object HD200775 within the reflection nebula NGC7023.

In a fraction of a second, the core of the Sun shuts off. It’s no longer pushing outward with its light pressure, and so the outer layers collapse inward, creating a black hole and a supernova. It sure looks like the build up of iron in the core killed it.

Is it true then? Is iron the Achilles heel of stars? Not really. Iron is the byproduct of fusion within the most massive stars. Just like ash is the byproduct of combustion, or poop is the byproduct of human digestion.

It’s not poison, which stops or destroys processes within the human body. A better analogy might be fiber. Your body can’t get any nutritional value out of fiber, like grass. If all you had to eat was grass, you’d starve, but it’s not like the grass is poisoning you. As long as you got adequate nutrition, you could eat an immense amount of grass and not die. It’s about the food, not the grass.

The Sun already has plenty of iron; it’s 0.1% iron. That little nugget would work out to be 330 times the mass of the Earth. If you gave it much more iron, it would just give the Sun more mass, which would give it more gravity to raise the temperature and pressure at the core, which would help it do even more fusion.

This image shows iron debris in Tycho's supernova remnant. Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al.
This image shows iron debris in Tycho’s supernova remnant. Credit: NASA/CXC/Chinese Academy of Sciences/F. Lu et al.

If you just poured iron into a star, it wouldn’t kill it. It would just make it more massive and then hotter and capable of supporting the fusion of heavier elements. As long as there’s still viable fuel at the core of the star, and adequate temperatures and pressures, it’ll continue fusing and releasing energy.

If you could swap out the hydrogen in the Sun with a core of iron, you would indeed kill it dead, or any star for that matter. It wouldn’t explode, though. Only if it was at least 8 times the mass of the Sun to begin with. Then would you have enough mass bearing down on the inert core to create a core collapse supernova.

In fact, since you’ve got the power to magically replace stellar cores, you would only need to replace the Sun’s core with carbon or oxygen to kill it. It actually doesn’t have enough mass to fuse even carbon. As soon as you replaced the Sun’s core, it would shut off fusion. It would immediately become a white dwarf, and begin slowly cooling down to the background temperature of the Universe.

Iron in bullet, bar, man or any other form isn’t poison to a star. It just happens to be an element that no star can use to generate energy from fusion. As long as there’s still viable fuel at the core of a star, and the pressure and temperature to bring them together, the star will continue to pump out energy.

What other exotic ways would you use to try and kill the Sun? Give us your suggestions in the comments below.

How Much Water Would Extinguish the Sun?

Have you ever wondered how much water it would take to put out the Sun? It turns out, the Sun isn’t on fire. So what would happen if you did try to hit the Sun with a tremendous amount of water?

How much water would it take to extinguish the Sun? I recently saw this great question on Reddit, and I couldn’t resist taking a crack at it: We know that the question doesn’t make a lot of sense.

A fire is a chemical reaction, where material releases heat as it oxidizes. If you take away oxygen from a fire, it goes out. But.. there’s no oxygen in space, it’s a vacuum. So, there’s not a whole lot of room for regular flavor water-extinguishable fire in space. You know this. How many times have we had to seal off the living quarters and open the bay doors to vent all the oxygen in the space because there was a fire in the cargo bay? We have to do that, like, all the time.

Our wonderful Sun is something quite different. It’s a nuclear fusion reaction, converting hydrogen atoms into helium under the immense temperatures and pressures at its core. It doesn’t need oxygen to keep producing energy. It’s already got its fuel baked in. All the Sun needs is our adoration, quiet, and yet ever present fear. Only if we constantly pray will it be happy and perhaps we’ll go another day where it doesn’t hurl a giant chunk of itself at our smug little faces because it’s tired of our shenanigans.

So, I’m still going to take a swing at this question… so let’s talk about what would happen if you did pour a tremendous amount of water on the Sun? Let’s say another Sun’s worth of H20. Conveniently, Hydrogen is what the Sun uses for fuel, so if you give the Sun more hydrogen, it should just get larger and hotter.

Oxygen is one of the byproducts of fusion. Right now, our Sun is turning hydrogen into helium using the proton-proton fusion reaction. But there’s another type of reaction that happens in there called the carbon-nitrogen-oxygen reaction. As of right now, only 0.8% of the Sun’s fusion reactions proceed along this path.

So if you fed the Sun more oxygen as part of the water, it would allow it to perform more of these fusion reactions too. For stars which are 1.3 times the mass of the Sun, this CNO reaction is the main way fusion is taking place. So, if we did dump a giant pile of water onto the Sun, we’d just be making Sun bigger and hotter.

Cutaway to the Interior of the Sun. Credit: NASA
Cutaway to the Interior of the Sun. Credit: NASA

Conveniently, larger hotter stars burn for a shorter amount of time before they die. The largest, most massive stars only last a few million years and then they explode as supernovae. So, if you’re out to destroy the Sun, and you’re playing a really, really long game, this might actually be a viable route.

I’m pretty sure that wasn’t the intent though. Let’s say we just want to snuff out the Sun. Vsauce provides a strategy for this. If you could somehow blast your water at the Sun at high enough velocity, you might be able to tear it apart. If you can reduce the Sun’s mass, you can decrease the temperature and pressure in its core so that it can no longer support fusion reactions.

I’m going to sum up. The Sun isn’t on fire. There’s no amount of water you could add that would quench it, you’d just make it explode, but if you used firehoses that could spray water at nearly the speed of light, you could probably shut the thing off and eventually freeze us all, which is what I think you were hoping for in the first place.

What do you think? What else could we do to snuff out the Sun?

How to See Airglow, the Green Sheen of Night

Emerald green, fainter than the zodiacal light and visible on dark nights everywhere on Earth, airglow pervades the night sky from equator to pole. Airglow turns up in our time exposure photographs of the night sky as ghostly ripples of aurora-like light about 10-15 degrees above the horizon. Its similarity to the aurora is no coincidence. Both form at around the same altitude of  60-65 miles (100 km) and involve excitation of atoms and molecules, in particular oxygen. But different mechanisms tease them to glow. 

Photo taken of Earth at night from the International Space Station showing bright splashes of city lights and the airglow layer off in the distance rimming the Earth's circumference. Credit: NASA
Earth at night from the International Space Station showing bright splashes of city lights and the airglow layer created by light-emitting oxygen atoms some 60 miles high in the atmosphere.  This green cocoon of light is familiar to anyone who’s looked at photos of Earth’s night-side from orbit. Credit: NASA

Auroras get their spark from high-speed electrons and protons in the solar wind that bombard oxygen and nitrogen atoms and molecules. As excited electrons within those atoms return to their rest states, they emit photons of green and red light that create shimmering, colorful curtains of northern lights.

Green light from excited oxygen atoms dominates the glow. The atoms are 90-100 km (56-62 mile) high in the thermosphere. The weaker red light is from oxygen atoms further up. Sodium atoms, hydroxyl radicals (OH) and molecular oxygen add to the light. Credit: Les Cowley
Green light from excited oxygen atoms dominates the light of airglow. The atoms are 56-62 miles high in the thermosphere. The weaker red light is from oxygen atoms further up. Sodium atoms, hydroxyl radicals (OH) and molecular oxygen add their own complement to the light. Credit: Les Cowley

Airglow’s subtle radiance arises from excitation of a different kind. Ultraviolet light from the daytime sun ionizes or knocks electrons off of oxygen and nitrogen atoms and molecules;  at night the electrons recombine with their host atoms, releasing energy as light of different colors including green, red, yellow and blue.  The brightest emission, the one responsible for creating the green streaks and bands visible from the ground and orbit, stems from excited oxygen atoms beaming light at 557.7 nanometers, smack in the middle of  the yellow-green parcel of spectrum where our eyes are most sensitive.

Airglow across the eastern sky below the summertime Milky Way. Notice that unlike the vertical rays and gently curving arcs of the aurora, airglow is banded and streaky and in places almost fibrous. Credit: Bob King
Airglow across the eastern sky below the summertime Milky Way. Notice that unlike the vertical rays and gently curving arcs of the aurora, airglow is banded, streaky and in places almost fibrous. It’s brightest and best visible 10-15 degrees high along a line of sight through the thicker atmosphere. If you look lower, its feeble light is absorbed by denser air and dust. Looking higher, the light spreads out over a greater area and appears dimmer. Credit: Bob King
A large, faint patch of airglow below the Dippers photographed last month on a very dark night. To the eye, all airglow appears as colorless streaks and patches. Unlike the aurora, it's typically too faint to see color. No problem for the camera though! Credit: Bob King
A large, faint patch of airglow below the Dippers photographed May 24. To the eye, airglow appears as colorless streaks and patches. Unlike the aurora, it’s typically too faint to excite our color vision. Time exposures show its colors well. This swatch is especially faint because it’s much higher above the horizon. Credit: Bob King

That’s not saying airglow is easy to see! For years I suspected streaks of what I thought were high clouds from my dark sky observing site even when maps and forecasts indicated pristine skies. Photography finally taught me to trust my eyes. I started noticing green streaks near the horizon in long-exposure astrophotos. At first I brushed it off as camera noise. Then I noticed how the ghostly stuff would slowly shape-shift over minutes and hours and from night to night. Gravity waves created by jet stream shear, wind flowing over mountain ranges and even thunderstorms in the lower atmosphere propagate up to the thermosphere to fashion airglow’s ever-changing contours.

Airglow across Virgo last month. Mars is the bright object right and below center. Credit: Bob King
An obvious airglow smear across Virgo last month. Mars is the bright object below and right of center. Light pollution from Duluth, Minn. creeps in at lower left. Credit: Bob King

Last month, on a particularly dark night, I made a dedicated sweep of the sky after my eyes had fully adapted to the darkness. A large swath of airglow spread south of the Big and Little Dipper. To the east, Pegasus and Andromeda harbored hazy spots of  varying intensity, while brilliant Mars beamed through a long smear in Virgo.

To prove what I saw was real, I made the photos you see in this article and found they exactly matched my visual sightings. Except for color. Airglow is typically too faint to fire up the cone cells in our retinas responsible for color vision. The vague streaks and patches were best seen by moving your head around to pick out the contrast between them and the darker, airglow-free sky. No matter what part of the sky I looked, airglow poked its tenuous head. Indeed, if you were to travel anywhere on Earth, airglow would be your constant companion on dark nights, unlike the aurora which keeps to the polar regions. Warning – once you start seeing it, you

Excited oxygen at higher altitude creates a layer of faint red airglow. Sodium excitation forms the yellow layer at 57 miles up. Credit: NASA with annotations by Alex Rivest
Excited oxygen at higher altitude creates a layer of faint red airglow. Sodium excitation forms the yellow layer at 57 miles up. Airglow is brightest during daylight hours but invisible against the sunlight sky. Credit: NASA with annotations by Alex Rivest

Airglow comes in different colors – let’s take a closer look at what causes them:

* Red –  I’ve never seen it, but long-exposure photos often reveal red/pink mingled with the more common green. Excited oxygen atoms much higher up at 90-185 miles (150-300 km) radiating light at a different energy state are responsible. Excited -OH (hydroxyl) radicals give off deep red light in a process called chemoluminescence when they react with oxygen and nitrogen. Another chemoluminescent reaction takes place when oxygen and nitrogen molecules are busted apart by ultraviolet light high in the atmosphere and recombine to form nitric oxide  (NO).

* Yellow – From sodium atoms around 57 miles (92 km) high. Sodium arrives from the breakup and vaporization of minerals in meteoroids as they burn up in the atmosphere as meteors.

* Blue – Weak emission from excited oxygen molecules approximately 59 miles (95 km) high.

Comet Lovejoy passing behind green oxygen and sodium airglow layers on December 22, 2011 seen from the space station. Credit: NASA/Dan Burbank
Comet Lovejoy passing behind green oxygen and sodium airglow layers on December 22, 2011 seen from the space station. Credit: NASA/Dan Burbank

Airglow varies time of day and night and season, reaching peak brightness about 10 degrees, where our line of sight passes through more air compared to the zenith where the light reaches minimum brightness. Since airglow is brightest around the time of solar maximum (about now), now is an ideal time to watch for it. Even cosmic rays striking molecules in the upper atmosphere make a contribution.

See lots of airglow and aurora from orbit in this video made using images taken from the space station.

If you removed the stars, the band of the Milky Way and the zodiacal light, airglow would still provide enough illumination to see your hand in front of your face at night. Through recombination and chemoluminescence, atoms and molecules creates an astounding array of colored light phenomena. We can’t escape the sun even on the darkest of nights.

How Life Could Have Produced Most Minerals On Earth

While astronomers are trying to figure out which planets they find are habitable, there are a range of things to consider. How close are they to their parent star? What are their atmospheres made of? And once those answers are figured out, here’s something else to wonder about: how many minerals are on the planet’s surface?

In a talk today, the Carnegie Institution of Washington’s Robert Hazen outlined his findings showing that two-thirds  of minerals on Earth could have arisen from life itself. The concept is not new — he and his team first published on that in 2008 — but his findings came before the plethora of exoplanets discovered by the Kepler space telescope.

As more information is learned about these distant worlds, it will be interesting to see if it’s possible to apply his findings — if we could detect the minerals from afar in the first place.

“We live on a planet of remarkable beauty, and when you look at it from the proximity of our moon, you see what is obviously a very dynamic planet,” Hazen told delegates at “Habitable Worlds Across Time and Space”, a spring symposium from the Space Telescope Science Institute that is being webcast this week (April 28-May 1).

His point was that planets don’t necessarily start out that way, but he said in his talk that he’d invite comments and questions on his work for alternative processes. His team believes that minerals and life co-evolved: life became more complex and the number of minerals increased over time.

Artist’s impression of a baby star still surrounded by a protoplanetary disc in which planets are forming.  Credit: ESO
Artist’s impression of a baby star still surrounded by a protoplanetary disc in which planets are forming. Credit: ESO

The first mineral in the cosmos was likely diamonds, which were formed in supernovas. These star explosions are where the heavier elements in our cosmos were created, making the universe more rich than its initial soup of hydrogen and helium.

There are in fact 10 elements that were key in the Earth’s formation, Hazen said, as well as that of other planets in our solar system (which also means that presumably these would apply to exoplanets). These were carbon, nitrogen, oxygen, magnesium, silicon, carbon, titanium, iron and nitrogen,which formed about a dozen minerals on the early Earth.

Here’s the thing, though. Today there are more than 4,900 minerals on Earth that are formed from 72 essential elements. Quite a change.

Hazen’s group proposes 10 stages of evolution:

  1. Primary chondrite minerals (4.56 billion years ago) – what was around as the solar nebula that formed our solar system cooled. 60 mineral species at this time.
  2. Planetesimals — or protoplanets — changed by impacts (4.56 BYA to 4.55 BYA). Here is where feldspars, micas, clays and quartz arose. 250 mineral  species.
  3. Planet formation (4.55 BYA to 3.5 BYA). On a “dry” planet like Mercury, evolution stopped at about 300 mineral species, while “wetter” planets like Mars would have seen about 420 mineral species that includes hydroxides and clays produced from processes such as volcanism and ices.
  4. Granite formation (more than 3.5 BYA). 1,000 mineral species including beryl and tantalite.
  5. Plate tectonics (more than 3 BYA). 1,500 mineral species. Increases produced from changes such as new types of volcanism and high-pressure metamorphic changes inside the Earth.
The official poster of the World Space Week Association 2013 campaign. Credit: World Space Week Association
The official poster of the World Space Week Association 2013 campaign. Credit: World Space Week Association

These stages above are about as far as you would get on a planet without life, Hazen said. As for the remaining stages on Earth, here they are:

  1. Anoxic biosphere (4 to 2.5 BYA), again with about 1,500 mineral species existing in the early atmosphere. Here was the rise of chemolithoautotrophs, or life that obtains energy from oxidizing inorganic compounds.
  2. Paleoproterozoic oxidation (2.5 to 1.5 BYA) — a huge rise in mineral species to 4,500 as oxygen becomes a dominant player in the atmosphere. “We’re trying to understand if this is really true for every other planet, or if there is alternative pathways,” Hazen said.

And the final three stages up to the present day was the emergence of large oceans, a global ice age and then (in the past 540 million years or so) biomineralization or the process of living organisms producing minerals. This latter stage included the development of tree roots, which led to species such as fungi, microbes and worms.

'The Moon rising behind a couple of palm trees with cows grazing in the foreground. As you can see in the image,  the bottom half of the moon has a different tint due to the earths atmosphere.' Credit:  Tom Connor, Parrish, FL
‘The Moon rising behind a couple of palm trees with cows grazing in the foreground. As you can see in the image, the bottom half of the moon has a different tint due to the earths atmosphere.’ Credit: Tom Connor, Parrish, FL

It should be noted here that oxygen does not necessarily indicate there is complex life. Fellow speaker David Catling from the University of Washington, however, noted that oxygen rose in the atmosphere about 2.4 billion years ago, coincident with the emergence of complex life.

Animals as we understand them could have been “impossible for most of Earth’s history because they couldn’t breathe,” he noted. But more study will be needed on this point. After all, we’ve only found life on one planet: Earth.

The STSCI conference continues through May 1; you can see the agenda here.