Tag Archives: science

Beyond the Pale Blue Dot

In all the gin joints, in all the world…

An old movie line, but it speaks a truth: life is miraculous to the point of being impossible. We search for it. To be fair, we’ve really only begun looking seriously in the last thirty years or so. The discovery of the first confirmed exoplanet in 1995 propelled us into the heavens, and we began to seriously believe we may just find life out there. Why not? That isn’t a scientific response, but life is incredibly improbable. The amount of unbelievable coincidences that enabled life to appear on our blue green marble almost beggars belief. Everything had to be just right, or life just never would have happened. Just like the proverbial bowl of porridge, which actually leads to the topic of this post. A certain famous little girl of fairy tale fame lent her name to the region around a star at which liquid water can exist in a stable form on the surface. More precisely, this region, or “Goldilocks Zone” is the distance from a star: the sweet spot where liquid water exists. To be more precise again, the Goldilocks zone is a function of stellar luminosity and output. The more energetic a star, the further out it’s Goldilocks or habitable zone is. It’s a fairly linear progression: the hotter the star, the more distant it’s habitable zone. Image: NASA/JPL Extremely simplistic, but that’s us in a nutshell. We happen to be just the right distance from our sun. Because life has only been found here (as far as we’re aware), we naturally think that life will tend to favour “earthlike” conditions somewhere else. That probably makes some sense. However, does all life in the universe necessarily exist on a rocky, watery world that essentially mirrors our own? It doesn’t have to be the case. Much recent thinking has been directed towards redefining the habitable zone. Our solar system is one of countless billions estimated to exist in our galaxy alone. As researchers discover more exo-solar systems seemingly every day it’s becoming apparent that perhaps our particular corner of the block is actually quite unusual. For astrobiology to have any relevance at all it’s important to think outside the square. For that reason we take a look at the habitable zone as we know it and stretch it’s limits.

The Local.

In our solar system we see a complex family of objects, all held together loosely by gravity. Many of these planets are suspected to possess water. Lots of it. In fact it’s believed by many researchers that the amount of water in the solar system not situated on earth is quite large. Our blue green marble is actually fairly arid compared to many other worlds in our solar system. The Galilean moon Europa is smaller than earth’s moon, but may hide two to three times more water than is found here! Earth is surprisingly dry compared to tiny worlds such as Europa, with the blue orbs representing an approximate comparison of each world’s respective water content. Europa is one of a small group of worlds in the solar system that have piqued the interest of astrobiologists over the years, as they are believed to possess certain sets of conditions and environments that could be conducive to the presence of life. Not just habitability (as was possibly the case with our Moon), but abiogenesis. Life arising from whatever hidden firmament lies within their icy depths. The reason these worlds give astrobiologists hope is that (quite naturally) exo-solar systems come in all shapes, sizes and flavours. Moons like Europa, Enceladus, or even now quite dead worlds such as Venus and Mars throw us tantalising glimmers of hope that Earth based life is not alone in the universe. These worlds (and others we discover) often possess sets of conditions assumed to be completely hostile to life: as we know it. However, even life as we know it has shown us that it can really go off script sometimes. Whole new classes of extremophilic organisms have been discovered, and are still being uncovered in some really nasty corners of the world which show one thing: life’s ability to shuffle pieces around on the evolutionary chessboard has enabled it to live almost anywhere: in space, nuclear reactors, and the earth’s mantle. Bacteria have recently been discovered in Antarctica which literally use hydrogen as a food source! These organisms suggest that the traditional concept of a habitable zone: the right amount of heat, light and atmospheric pressure as we observe on earth need not necessarily apply to alien planets.

Tidally locked exoplanets

These are worlds which orbit their star(s) with one side permanently facing inward. The obvious ramifications of this: the side facing the star obviously has a much greater actinic flux than the planets night side. Translation: it is likely a scorched wasteland, where temperatures are oven-like. On the dark side we expect to find extremes of temperature at the opposite end of the scale. This side would be frozen and permanently dark. Overall, the planet doesn’t seem to hold much hope for life. It is believed that a good percentage of confirmed explanets are locked into tight orbits around their stars. Often these worlds take a few days (or less) to complete an orbit, and they are most likely tidally locked as a result. But all hope is not lost. The discovery of water ice in permanently shadowed craters on worlds as hostile as mercury and the moon leads many researchers to believe similar regions could exist on tidally locked exoplanets. Such water filled craters lie within the Terminator, the boundary between a planets day and night side. On a larger object such as an exoplanet, small strips of habitability could exist, situated in literally a permanent twilight zone. Twilight Zones of habitability could be a surprising spot for life to appear… In such a situation, the habitable zone as we define it would not be as dependant on distance from a star.

No Habitable Zone?

The recent discovery of two rogue planets lends itself to another interesting scenario. These rogue worlds are planets which aren’t gravitationally bound to a solar system. They are believed to be quite common. Current estimates have the complement of wandering worlds in the milky way galaxy at approximately two billion. How could such exotic locations possibly host life? Because geothermal or tidal heating could provide conditions in which life could possibly eke out a niche. Tidal heating is a mechanism for internal heating which has been observed in several frozen, distant worlds in our own solar system. Europa (mentioned above) and Enceladus likely possess subsurface oceans of liquid briny water. The heating for this comes from the gravitational stresses caused by interactions with nearby worlds. In the case of Europa and Enceladus their elliptical orbits around Jupiter and Saturn respectively cause an ebb and flow of tidal flexing in their rocky cores. Such frictional heating may even give rise to fissures and hydrothermal vents providing possible locales for biogenesis, as may have been the case here on earth. These frozen worlds appear lifeless, but appearances could be deceiving. Whilst far beyond the habitable zone of this solar system, the presence of life on either world would lead to further redefinition of habitable zones. Exoplanets are believed to number in the trillions in this galaxy and the recent discovery of the first known exomoon suggests that moons could be even more numerous. After all, in our solar system moons and natural satellites outnumber the planets by ten to one. Habitability on any of these worlds opens up the options for researchers observing distant solar systems for signs of life.

To the Weird..

Last but definitely not least. A benchmark of habitability as we define it for earth based life is that, overall, the environment should be fairly benign in order for life to have a chance. Earth itself only became habitable after billions of years of incredible geological upheaval and intense bombardment from outer space. Not only that, the presence of a thick atmosphere afforded protection from cosmic rays pumped out by a young sun. A class of exoplanets known as super earthsmay be able to support life despite often being in orbit around extremely energetic stars such as red dwarfs. These stars are tiny, often having only ten percent of the mass of our sun, but they are nasty. Frequently they have been seen producing extreme solar flare activity. This image shows a solar flare being generated by the red dwarf star DG Canum Vernaticorum (DG CVn). To put it in perspective the most powerful solar flare observed on our sun was rated X45 on a standard scale used to gauge glare events. In comparison DG CVn was rated X100,000: 10,000 times more powerful! At its peak the DG CVn flare reached temperatures 12 times hotter than the core of the sun! NASAs SWIFT observed this event over 11 days, recording the most powerful flare ever recorded. Image: NASA/SWIFT It stands to reason that any nearby planets would be baked into oblivion by the levels of energy being produced during such events. But larger rocky worlds such as super earths could provide a slim chance of life. Super earths are rocky worlds ranging in size from three to five times larger than Earth. Their mantle and outer layers could act as a shield against radiation, enabling any lifeforms present to carry on in subsurface biospheres, akin to recently discovered microbial biospheres deep in the earth’s crust. Lifeless surfaces could hide thriving ecosystems throughout the galaxy, or even beyond. Even neutron stars could harbour life bearing worlds if conditions are just right. These stellar objects don’t seem like an ideal location for life, but again a suitably large and dense world could provide safe harbour against lethal X-rays and other electromagnetic nastiness. Small worlds could be destroyed if they strayed too close, but if a super earth lay at a safe distance, who knows?

A Final Thought….

In this overview it’s been shown that life can theoretically exist outside the traditional confines imposed by earth based habitability criteria. However, I’ve only looked at planet based life… Who knows what else is out there? That’s a whole new type of thinking. Thanks for reading! I have a new video coming, which will be based upon this blog post. In the meantime, here are some speculations on a habitable moon in the distant past. P. S.. I have recently set up an online store, featuring my designs on a range of products, any of which would make fantastic and unique gifts! Take a look: https://www.redbubble.com/people/AstroBiological?asc=u All images © AstroAF Designs unless specified in image caption.
Advertisements

Life Around a Failed Star..

While NASA’s Parker Probe delves into the mysteries of our own sun, other objects known as brown dwarfs taunt us, adrift in a limbo between star and gas giant.

Could Life Survive Around a Failed Star?

November 2, 2018

To date, a little over 3700 exoplanets have been discovered. Many of these owe their discovery to the Kepler Space Telescope, which as of writing this post has been retired by its masters. Thank you Kepler.

Not all of these planets are habitable. Far from it in fact. Only about 55 “Earthlike” planets have been earmarked for a closer examination. With an estimated 2 trillion planets in the Milky Way galaxy alone, this tiny group of maybes doesn’t seem to hold out much hope for the astrobiology crowd. In order to simplify things a little, researchers generally look for life as we understand it, in environments we can understand. A world with a mild climate, liquid water, with life employing carbon is the rule of thumb.

It’s a big universe though, and life not as we know it could be the norm. What kinds of lifeforms could exist in environments in which life on earth could never arise?

In the atmospheres of gas giants? On frozen worlds? What about rogue planets: worlds not tethered to a solar system. These wanderers could be common in this galaxy. What about brown dwarfs?

What is a brown dwarf ? Often they are referred to as brown dwarf stars, and this gives some clue as to their nature. Literally, a brown dwarf is a failed star. That is to say, a brown dwarf is a former protostar which has failed to reach the critical mass required for star hood. Far from being underachievers though, brown dwarfs are interesting to exoplanet researchers. These mysterious objects exhibit properties of stars and planets.

A rogue planet is a wandering planet: homeless so to speak. How is this important for exoplanet research? In my most recent video I talked a little about some of the difficulties faced by astronomers when attempting to directly image exoplanets.

The images don’t look like much. One problem with direct imaging is that the light from host stars get in the way. Brown dwarfs circumvent this by often being standalone objects, enabling researchers to examine these “pseudoplanets” (pseudostars?) and learn more about exoplanet characteristics and behaviour.

What about their starlike features?

A star is an object which uses fusion of elements such as hydrogen or helium to produce heat and light. Other stars fuse heavier elements, but we’ll just avoid that fork in the road today 😉

This is a red dwarf star at work. The heat and light produced by this little monster could support life in other solar systems. TRAPPIST-1 is a well known example.

This is an artists impression of a typical brown dwarf. Generally much more massive than Jupiter, our own big guy, this object may undergo limited fusion of heavier elements such as deuterium.

Of even more interest to astrobiologists: brown dwarfs could be capable of supporting life! Not in themselves as such, but several brown dwarfs are known to possess their own planetary systems.

Let’s add a planet to this image. A planet in orbit around a brown dwarf may be heated by tidal stresses. Worlds such as Europa in our solar system lie far beyond the habitable zone surrounding our sun, yet may theoretically harbour life in a subsurface ocean heated by tidal forces. Hypothetical worlds orbiting brown dwarfs could experience something similar.

Of course, as I have pointed out to me all the time, life is fairly fussy, and requires a fairly stringent catalogue of conditions and contingencies. We can still dream right? After all, what’s the point of astrobiology if not to colour outside the lines a little?

Or a lot?

Find me on YouTube and while you’re at it, some other posts on this blog require your attention!

For some bizarre reason, I can’t caption images right now. All images produced by Ben Roberts, with the exception of image two, which was produced by the European Southern Observatory Very Large Telescope.

39 Light Years: Part Two

Shared Ecosystems

NB: This is a speculative piece.

For 39 years images and data have been streaming across space. A small flotilla of missions to the TRAPPIST-1 system has begun transmittting. Seven small rocky worlds, all at least nominally Earthlike have drawn their share of attention over the decades. They huddle tightly around an angry little red dwarf star, somewhere in the Aquarius constellation.

Some of these planets sit within the habitable zone of TRAPPIST-1, that sweet spot where the temperature is just right: the proverbial bowl of porridge. Just right for what?

For water to exist in liquid form on the surface. And some of these worlds are very watery. Long ago the James Webb Space Telescope spotted water and indications of seasonal change on several of these worlds. Spectroscopic analysis enabled us to see these worlds with different eyes.

The missions now assigning themselves to various locales in this system show us a family of worlds possibly bearing life. TRAPPIST-1e is the prime target, but each world has a story to tell.

First approach showed us a red planet, with signs of vigorous atmospheric activity. There appears to be a purple tinge to the four large landmasses straddling this globe.

This purple haze is a striking feature of the planet. It may be due to native organisms using a photosynthetic pigment such as retinal. This protein may have been employed by early photosynthesisers on earth. Chlorophyll may have been a later card to be added to the deck.

Aerial observations

TRAPPIST-1e appears to possess a diverse set of environments. Overall, it is a temperate world, and any life does struggle with sometimes extreme solar flare activity from TRAPPIST-1 .

Dust storms are a feature of TRAPPIST- 1e. In the above image a drone has spotted one such dust storm on the horizon as it flies over a large inland body of water. It is twilight in this image.

The TRAPPIST-1 worlds are close. The orbits of all seven planets would fit within the orbit of Mercury back home.

Traces of green can be noticed on the slopes of this extinct volcano. TRAPPIST-1 is believed to be ancient: on the order of eight to ten billion years. It’s family of seven worlds may have seen life arise more than once. This may have happened on our own world, with an enigmatic array of creatures known generically as Ediacarans appearing before the more conventional forms we see today.

The proximity of the TRAPPIST-1 planets presents an opportunity for researchers to observe lithopanspermia. The Swedish chemist Svante Arrhenius was one of the earliest scientists to suggest that life or it’s building blocks could travel from world to world, hitching a ride on moving objects such as comets or asteroids. Lithopanspermia builds on this. It’s a big idea, and observations on several of the TRAPPIST-1 worlds is showing us something we’ve only speculated on. Life travels between worlds, carried by rocks sent into space by impacts and volcanic eruptions.

Were a visitor to be admiring the sunset on, say, TRAPPIST-1d, they’d be in for a treat.

In this system, life is not restricted to one world. Here, an ecosystem interconnected by space borne life has given rise to an interplanetary ecosystem.

Next time, we visit a frozen world that may be hiding it’s own life, far beyond the habitable zone of TRAPPIST-1.

Read some other posts and tell me what you think! Also, please do me a favour and check out my YouTube channel:

All images: Ben Roberts

The Lost Moon

Boom. Image: Ben Roberts

The moon is one thing we all have in common. I’ve always loved looking up at it. Whether it’s from a religious, mythological or scientific perspective, Luna holds a powerful mystique regardless. The story of the moon is written into the story of life itself.

What does the colossal impact taking place in the above picture have to do with the moon? Because it’s likely the moon formed via a process of accretion.

Around four and a half billion years ago, earth itself had only just coalesced from a cloud of gases and dust that eventually gave rise to the entire system.

Image: Ben Roberts

Earth is believed to have formed without a moon. In fact earth as we know it today formed as a result of the moon.

Picture this. Earth is newly formed. It’s a toxic planet with vast tracts of it’s surface covered by a magma ocean.

Image: Ben Roberts

From the outer solar system it comes. An object roughly the size of mars slams into Earth 1.0. The object has been named Theia. This impact is catastrophic, essentially tearing away the outer surface of our world.

Image: Ben Roberts

Where does all of this crust go? Into space, forming a ring around the newly resurfaced earth. It is this ring, consisting of the fragmentary remains of both our world and Theia, that will accrete to form the moon.

That’s the moon in a nutshell. It’s influence on the course of life has been fundamental, with a critical role in climate and seasonality via the key role it plays in tides. For over four billion years the moon has stared down upon the world, seeing the march of life with all of it’s ups and downs.

Has the moon itself been lifeless all this time? It’s been our closest neighbour for practically forever. We have always thought of the moon as a dead, hostile place. Today it certainly is. With no atmosphere to speak of, negligible water and lethal solar radiation bombarding it’s surface, the consensus of opinion is that the moon is completely devoid of life.

Image Credit: NASA/GSFC/Arizona State University

But it may not always have been like this.

It may be a stretch, but several studies have suggested that at least for a time the moon may have been at least habitable. Perhaps not an oasis of life, but a place that could harbour it.

The moon may not quite have looked like this, but volcanic activity (seen on the limb) would definitely have contributed atmosphere. Images: Ben Roberts

How is this viable? As noted, we all know the moon is hostile to all life. However, the moon is now an inert world, devoid of any geological activity.

Once, though, the moon was anything but inactive. In the period after the moons formation, around four billion years ago it was highly volcanically active.

A habitable moon more likely looked something like this. Image: Ben Roberts

Intense volcanism can be a source of atmospheric gases. This is definitely a factor on earth. Many atmospheric gases, including several trace greenhouse gases are pumped into our skies by volcanoes. Greenhouse gases are pivotal in regulating climate on earth. On the moon all those billions of years ago, volcanoes may have done something similar, bulking up the lunar atmosphere and enabling this tiny world to retain some heat. In addition, a thick atmosphere provided protection against solar radiation and an environment amenable to liquid water. Water is, as we know, crucial to all life on earth. “Follow the water” is one of the central catch cries of astrobiology. Find water, the reasoning goes, and life may be there.

This isn’t always the case though. Water exists almost everywhere in the solar system. There is even water vapour on the sun! There is plenty of water on the moon, locked up as ice in several craters in permanent darkness.

How would all this water have arrived on the moon? Prevailing theory regarding the origins of earth’s water held that much of it was delivered by cometary impacts. This is certainly reasonable. Recent discoveries though hint at vast reservoirs of water locked up deep within the planet itself. Water may be replenished over the eons by outgassing from volcanoes for example. This could have happened on the moon. Several studies of lunar composition have demonstrated that there may be similarly vast amounts of water locked up within the moons core. The ancient moon may have gained a thick watery atmosphere from centuries of volcanic activity partially terraforming it.

So, to put a long story short, water by itself is no guarantee of habitability. The moon, however, may once have been a very different place. With a thick atmosphere providing protection from cosmic rays and allowing pools of liquid water to form, life could have quite easily gained a foothold there. Most likely this life was in the form of unicellular organisms which may have arrived via lithopanspermia. This is a process whereby worlds at close proximity can exchange life or it’s building blocks via impact or volcanic ejecta.

Lithopanspermia: is it a thing? Image: Ben Roberts

This very concept is being applied to crowded systems of exoplanets such as the TRAPPIST-1 system, and is an exciting avenue to explore. In such a system, the possibility of interplanetary ecosystems could exist! This is, of course, very theoretical, but damn what an interesting idea!

What do you think? Was the moon ever habitable?

While you’re at it, check out my tiny little YouTube channel, giving you the universe in plain human!

39 Light Years: Part One

Image: Ben Roberts. Produced with Universe Sandbox

Sometime in the early 2000s, this place was still a speck of data in some astronomers brain. The announcement of a system of seven earth-sized planets was pretty big. The further revelation of three of those worlds sitting within their stars habitable zone was the icing on the cake.

As the first intelligent explorers approach TRAPPIST-1e, we present to you these images: the culmination of decades of waiting, hoping that return transmissions from the TRAPPIST-1 mission wouldn’t get lost in interstellar space. There were those who worried that anything beamed back by the missions wouldn’t even make it out of the system. TRAPPIST-1 is a red dwarf star: a tiny relic of a thing but incredibly ancient. Age estimates range from 8 to 12 billion years old. Red dwarf stars tend to be nasty little suckers, and TRAPPIST-1 is no exception. Extreme solar flare activity sometimes hits the system, as the parent star has a tantrum. Communication from the system is nothing short of a miracle. Nevertheless, here are some of the better images we’ve managed to glean from the stream of data being sent back. Thirty nine years worth. Thirty nine years of waiting.

Approach: A New Red Planet

The very first direct images of TRAPPIST-1 and it’s rocky retinue were messy little blobs of pixels.

Of course, many exoplanets (and exomoons) had been imaged directly using a variety of techniques. The use of coronagraphs to scrape together images from points of light across impossible distances was revealing new vistas for a long time. The following image was taken all the way back in 2004:

A disc of debris around the red dwarf star AU Microscopii. Image: Hubblesite.org

Of course, progress marched on, and as missions approached the system the world waited for new images. A first blurry image sped across the galactic neighbourhood:

A TRAPPIST-1 planet caught in transit across the host star. The faded object to left of centre is an artifact of the imaging process.

This image was a first test. As the mission approached the system, we began seeing more. High quality imaging was held off until final approach, in the interests of energy efficiency.

An infrared and monochromatic direct light image, taken from a distance of approximately 11 AU. Images: Ben Roberts

TRAPPIST-1e was waiting for us.

Image: Ben Roberts

Imaging of exoplanets is explored in a new video, presenting the concept of coronagraphy. Help astrobiology reach the world (this and others) by checking it out. Subscribe and share if you like.

This post is the first of a series taking us on a trip to a real alien world, and speculating on just what it could be like, using real world astrobiology. I hope you like it!

The Last Ecosystem

Fragments of ancient life, spotted by explorers in a new system..

I’ve been working on some more astrobiology art. It’s taken on a life of its own, and I have to say, I’m paying more attention to these images than my YouTube channel!

I’ve been enamoured lately of dead or dying worlds. A recent video on my channel talked about the amazing possibility of limestone fragments orbiting the white dwarf star SDSSJ1043+0855. Ever since reading of this it’s captured my imagination. The notion that life has existed long ago, possibly before life began on earth bears thinking about.

Limestone is a mineral produced primarily by organisms which produce shells, using a matrix that incorporates calcium carbonate. In the early days of multicellularity, as the predator-prey paradigm took hold of Darwinian evolution, an ancestor of today’s molluscs discovered how to make use of an upsurge in calcium levels in the oceans. It used it to produce a protective suit of armour. This trick was so successful that molluscs became incredibly abundant. So abundant, in fact, that their remains ended up as vast deposits of limestone.

To the present day.

Using spectroscopy, the three elements that comprise calcium carbonate: carbon, oxygen and calcium have been detected in the upper atmosphere of this particular white dwarf. By themselves they aren’t a smoking gun. It’s also fair to point out that limestone can form abiotically. Limestone deposits in subterranean caves are one example. However, the vast majority of limestone on earth is biologically produced.

The “limestone” orbiting this star is believed to be embedded in the fragments of a large rocky object. We know nothing about this world, only that it probably existed and (possibly) limestone comprised part of it. Is it a fossil, spotted across the light years by modern humans? How long ago did this world harbour life? White dwarf stars (which aren’t technically stars! Find out why here) have been discovered which are nearly as old as the universe.

Earth is 4.6 billion years old. What of the world currently being torn up by the immense gravity of this white dwarf?

Dead worlds could be scattered across the galaxy.

It would be interesting to look forward and see how our own world eventually will die. For now, this white dwarf star and it’s companions are a way to look ahead at what may befall us. It’s believed that eventually the earth will become incapable of supporting life, as the sun begins to undergo senescence billions of years from now. What iterations will the terrestrial biosphere take over such a vast stretch of time? Will life start over? Are these “fossil” fragments within this unnamed rocky world pieces of its last ecosystems?

What will the last ecosystem on earth be?

Sailed the Ocean Blue

It’s been estimated that a good percentage of planets beyond our solar system may be water worlds.

We here on mother Earth like to think of our blue green marble as a water world. Indeed it is watery, and water is pretty much the reason anything lives here at all. That’s why astrobiologists naturally seek signs of water on exoplanets. “Follow the Water” is a central tenet in the search for extraterrestrial life.

But compared to some worlds, earth really isn’t that waterlogged at all. It’s 0.002 percent water by mass. Only a tiny fraction of that water is available to terrestrial life. That water which isn’t directly involved in biological processes is linked to them, linking life to the planet via seasons and climate.

Some exoplanets are believed to be up to fifty percent water! These are true ocean worlds. To date, up to thirty five percent of exoplanets larger than may be covered by vast layers of water that may or may not harbour life. The jury is well out on that, but the idea is intriguing (and tempting) as the traditional definition of habitable zones is being stretched and reinterpreted.

A water world with a thick atmosphere of steam.

For now, we have only our imaginations with which to explore these worlds…

An aerial view of remote coastline on a hypothetical watery exoplanet.

A new video!