Settle The Stars – Mars

Settle The Stars – Mars

Hello folks, this is Alexander Winn.  

Today we’re visiting one of the most popular destinations in our solar system: Mars.  The Red Planet has been the subject of countless sci-fi adventures from the time that mankind realized it was a place we could visit.  From the 1800’s when observers first believed they saw artificially created canals on the surface right up through today we have hoped to find life on another planet, and Mars has taken center stage in the search for aliens.

Our trip to Mars will take us face-to-face with some of the most massive geological features and mysterious eccentricities that exist in our solar system – and we’ll learn about what they are still teaching us about Mars, Earth and the rest of the solar system.  Interspersed throughout the journey we’ll see examples of past observations and scientific theories have been challenged and shaped by continuous study and reflect on some of the cultural and historical impacts of the planet that we carry even today.

Today’s visit will be imaginary, but it might not be long before you can book your own ticket to Mars.  There are several space agencies and private corporations currently racing to be the first to offer passage to the planet.  The current front-runner is SpaceX, the venture headed by Elon Musk.  So far several successful tests have been conducted with unmanned visits to Mars slated for around 2025.  SpaceX hopes to begin large-scale commercial trips in the 2030’s, so intrepid explorers should begin saving now as a ticket could cost you up to half a million dollars.

Fortunately for us, today’s visit is free, safer, and thankfully… shorter.

The real deal will be a grueling seven-month swing through space in what’s known as a transfer orbit – instead of making a direct line from Point A to Point B, space travel requires a little more finesse.  Planetary alignments are carefully calculated to anticipate future locations before the craft is lobbed like a shot-put from one planetary orbit to another.  Dates and times are important here, and if you miss your launch window you could find yourself stranded (on Earth or on Mars) until the next favorable alignment.

Seven months is no time at all to an astronomer, but to a traveler it can seem an eternity once the novelty of life in zero gravity wears off.  For most of the journey there won’t be much to see out the windows aside from the stunning starscape, but some exercise to prevent atrophy and a couple hundred in-flight movies should help pass the time.

As Mars approaches you will have a rare view at the inspiration for uncountable millions of humans who have gazed up at the planet from Earth.  The deep orange-red color of abundant iron oxide represented blood and fire to many ancient stargazers – small wonder that the planet became associated with war, fire and destruction to many of them.

Many know Mars to be the Roman god of war, carried over from the Greek god Ares – in fact, in modern Greek the planet is still referred to as Ares.  But such a prominent and unique object in the sky was the focus of interest for many other cultures, including the Chinese who named the planet the “fire star” which is an omen which also foretells the coming of war, bloodshed and destruction.  In Sanskrit the planet is called Angaraka, after another deity of war.  But not all cultures attributed the red color to calamity – the ancient Egyptians named the planet for the red god Horus in charge of kingship and the sky, and ancient Hebrews called it Ma’adim, or “the one who blushes”.

The symbol of the circle and projecting arrow that many recognize as the symbol of the male sex was first seen from manuscripts in the Middle Ages to represent the planet as well as the element of iron.  The symbol is actually a pictograph depicting an ancient shield and spear, holdovers from the cultural association with war.

From the window of our ship, it is clear no wars are currently raging on Mars, in fact from here it appears still and quiet.  Even though we’re close, the smaller size creates an illusion of distance as the curvature of the planet is much more pronounced than Earth would be at this altitude as Mars is only about half the diameter of Earth.

Depending on the timing, you may be able to see the two moons of Mars, Phobos and Deimos named after the Greek god Ares’ children.  Evidence suggests that the moons are composed of materials normally found in asteroids, leading to one theory that they are actually foreign objects captured by the planet’s gravity – but there are also clues that support another theory that Phobos could have originated from materials ejected from Mars itself as the result of a massive impact event.

Invisible from our little window are our Earth visitor predecessors also circling in orbit around the planet.  There are about a dozen man-made satellites currently circling Mars, some long dormant, some still busily collecting data.  Beginning with the first successful flyby in 1965 by NASA’s Mariner 4 probe and first ever successful orbit achieved by Mariner 9, the constellation of spacecraft has only grown.  Most of the satellites still in orbit today are too small to be viewed from our vantage point – if they were, they’d probably be a little too close for comfort.

Evidence of past calamities is clearly visible though, from massive scars still visible on the surface.  The southern half of the planet is pockmarked by craters from ancient collisions.  Large meteors have little difficulty reaching the surface through the thin atmosphere, visible from here as a thin band on the horizon.  

By contrast, the northern part of the planet is relatively smooth.  These are vast plains, flattened out by lava flows millions of years ago.  One theory is that billions of years ago Mars was impacted by a massive object hundreds of miles across.  That would make Mars the site of the largest known impact crater in the solar system, as large as Europe, Asia and Australia combined.

Shining bright white against the reddish-brown soil we can clearly see the polar ice caps, one of the most promising early discoveries about the planet.  Finding frozen water on one area of the planet while being absent from other areas could suggest an intermediate zone where liquid water can exist.  Such a zone would bode very well for the hope that Mars could be capable of supporting life – either Martian life in the past or visitors from Earth in the future. 

As we descend for landing, some of the major geological features of the planet become more pronounced.  Great mountains begin to rise up, with valleys, plains and even canyons carved throughout the landscape.  One mountain in particular is unmistakable: Olympus Mons.

The gargantuan shield volcano is easily visible from space, and one of the largest volcanoes in the solar system.  Towering two and a half times as high as Mount Everest, the shield volcano sprawls over an area roughly the size of France.  We could visit it up close, but ironically it wouldn’t be all that impressive – the shield is so large that the curvature of the planet would prevent us from seeing the entire profile of the mountain.  Even if you perched right on top, the bottom would be out of view.

Another unmistakable feature to point out on our way down is the massive system of canyons known as Valles Marineris.  This sprawling network of canyons stretches over 2,500 miles across the face of the planet and gouges nearly 23,000 feet deep.  If you were perched on the edge, the opposite canyon face would be up to 120 miles away – way too far to even see across.

The Valles Marineris and Olympus Mons appear to have formed around the same time as each other, along with a huge number of other massive volcanoes and lava plains on the planet during the violent Heperian Period of Mars’ geological history which ended about three billion years ago.  During this cataclysmic transformation, Mars experienced planetwide volcanic activity and catastrophic flooding which carved massive canyons across the planet’s surface.

Now safely aground at our landing site, it would be hard to believe such a period of upheaval happened here.  The ground is rocky and flat, and the sparse atmosphere whips up the dust to welcome us after our long journey.

One of the first stops as tourists has to be to visit an old friend.  Not far from where we landed, a small metal rover waits for our welcome.

This particular one is called Sojourner, and it’s been waiting for us here since 1997.  NASA lost contact 85 days into what was supposed to be a seven-day mission, and it’s been here accumulating dust and awaiting rescue.  About the size of a dog with six wheels and a little solar panel, this experimental rover allowed NASA scientists to develop new methods for movement and control that would improve later designs.  Slowly and carefully (as Sojourner’s top speed was about 1 centimeter per second) it managed to journey 330 feet from its home base.  And now with us here, Sojourner can retire to a pampered life in Mars’ first museum.

Since the first successful rover Mars 3 achieved by the Soviets in 1971 there have been seven sent to the planet over the years, with two NASA rovers currently active on Mars right now (Curiosity and Perseverance), and the Chinese Tianwen-1 is en route to join them shortly.  The seven rovers are spread out across the planet so we can’t visit them all on our trip today, but they have collected invaluable information about the atmosphere and geology of the planet that continue to make a human mission to Mars a reality.

One of the most daunting challenges faced by engineers designing these manned and unmanned missions is this dust – all this dust.  It’s exceptionally fine, like talcum powder, and covers the planet so completely that no environment is spared.  For mysterious reasons, it even kicks up into massive planet-wide dust storms every few years.  The dust can cover camera lenses and solar panels, clog mechanical components and disrupt radio communications.  It will be a major part of life for early Martian explorers, and has already been the bane of several rover missions so far.

The dust is carried on the wind of Mars, which can blow quite strongly considering how thin the atmosphere is.  The air pressure is exceptionally low compared to Earth, less than 1% of what we’re used to.  At that pressure, the air must move at a high velocity to mobilize dust, and wind speeds have been clocked at an average of 10 to 20 miles per hour, reaching as fast as 70 miles per hour in a dust storm.

Compared with the nitrogen and oxygen-rich air we breathe on Earth, the atmosphere on Mars is almost entirely composed of carbon dioxide.  It is a heavily oxidizing atmosphere, which explains the rich orange-red color of the planet imparted by the iron oxide present in the dust and soil.

As we look around, the sky is colored a similar reddish orange, thanks to the dust particles, but as the sun sets we can look forward to a brilliant sunset of orange and gold that changes to a lavender and blue twilight against a curtain of high-altitude clouds.  As night gradually falls (twilight lasts a bit longer with light scattering through the dust in the air) we would see the stars shine.  The dust dims them about a magnitude of brightness, but that’s still better than you’ll get in most suburbs on Earth due to light pollution.  And here on Mars they don’t seem to shimmer and twinkle – the atmosphere is too dim for that.

Nighttime also gives us a better sense of the movement of the planet we’re standing on.  A day on Mars is remarkably close to a day on Earth – only 39 minutes and 35 seconds longer than we’re used to.  If you’re curious how adjusting to the new sleep schedule is, just ask the NASA engineers responsible for keeping Curiosity and Perseverance busy all day.  They keep a Martian schedule for their work, though the payroll department probably finds it less entertaining.

Not that we’re bothered thinking about pay while looking at the Martian night sky.  In the east we can watch Phobos rise from the western horizon and march across the sky quickly, setting again in the east after taking only 11 hours to cross the sky.  It appears to us as only a third of the size of the moon, but the pale color would make it stand out like a bright pebble.

Deimos, on the other hand, rises from the east and sets in the west – not because it moves in the opposite direction, but because its orbit is much slower than Mars rotates on its axis.  It is larger than Phobos but much farther away, so to us on Mars it would appear more like a very bright star.

If we had visited in 2014, we would have had a spectacular show indeed.  The comet Siding Spring made a close pass of Mars – so close, in fact, that the entire planet may have been engulfed in the tail-like coma for a brief time.

As for other light shows we might enjoy, you might have heard of an aurora phenomenon detected on Mars back in 2016.  Unfortunately, we wouldn’t be able to view the sky lights ourselves, as the light show is only visible in the ultraviolet spectrum during the day.  But our electronic sensors can sure enjoy the spectacle, and they’ve taught us a lot more about Mars.

On Earth the aurora is caused by the collision of charged particles from the sun with molecules in our upper atmosphere.  They only occur near the poles because these charged particles slide off the planet’s magnetosphere like water across a giant balloon, circling around to the poles where the magnetic field originates and sparking the light show.

Mars has only vestiges of a magnetosphere left.  The magnetic field collapsed about four billion years ago, theoretically after taking several large hits from asteroids.  Without the planetary shielding, the Martian atmosphere has gradually been stripped away by the solar wind.  NASA’s MAVEN orbiter studies the upper atmosphere of Mars, and according to the data collected it appears the planet was once surrounded by a more robust, humid layer of air before it was lost to the sun’s energy.

After a night of stargazing, a new Martian day means more exploration for us here on the surface.  One of the most important places for us to visit has been impenetrable for our orbiters and landers so far, and the most promising for well-preserved evidence of life-supporting conditions: caves.

A series of cave entrances has been spotted by one of NASA’s satellites along the face of Arsia Mons, a large volcano in the Tharsis Basin southeast of Olympus Mons.  Likely formed as part of the volcanic process, these caves are well protected from meteoroid impacts, erosion and damaging radiation from the sun.  Obviously, they’re impossible for a wheeled, solar-powered rover to explore, but for humans a little off-world spelunking is Space Exploration 101 so we can get a close first look ourselves.

Inside we might find evidence of liquid water, either in molecular traces, water-requiring mineral deposits or flow erosion.  All these clues have been spotted elsewhere on the planet, usually in the basins of craters or up against sheltering cliffs and mountains.  In 2018 and 2020, large salty lakes of liquid water were detected by the European satellite Mars Express.  As hypothesized, these lakes only exist underground as far as we know, where the sun’s radiation can’t reach them.

It is a testament to the power of the long-term forces of transformation at work at the planetary scale, to find so much evidence of flowing rivers, torrential floods and even oceans all around us – but not a drop to be found on the surface today.

Even if hidden underground or locked in icy stasis at the poles, the presence of water bodes well for the ability of any planet to sustain life.  On Earth we have learned that life has a way of surviving in even the most unimaginable conditions, but one condition is essential: water.  Water dissolves life-giving substances and allows necessary chemical reactions to take place.  It can also act as an insulator, stabilizing temperatures to make it easier for fledgling life to gain a foothold.  Life as we would recognize it is simply impossible without water.

Alongside H20, there is one other essential chemical component generally understood as essential for life: carbon.  The multi-tool of the periodic table, carbon’s unique expertise as a molecular brick-and-mortar building block makes it the go-to backbone of essential molecules from sugars to proteins and everything in-between.  Fortunately, with an atmosphere rich in carbon dioxide, Mars has carbon in spades.

So, we have spent time searching for the requirements life needs to survive, but what about the outputs it generates?  Can we detect evidence of life by looking for byproducts of living processes?  As it turns out, we’ve been looking there, too.

A common metabolic product of living organisms is a simple molecule called methane.  Methane doesn’t last long in the wild, especially in a radiation-rich atmosphere of Mars, so it’s presence would mean an active source.  As it turns out, satellites around Mars have detected large plumes of methane on the planet which suggest localized points of origination somewhere near the surface or deep underground.  Scientists and E.T. enthusiasts should keep their excitement in check however, as there are several geological processes that could produce similar plumes.  But it is a very promising sign that will require further confirmation.

Even if life does not currently exist on Mars, it is possible it once could have in the past.  And these possibilities are encouraging to some who believe that what was once possible could be possible again.  While still far outside the realm of scientific reality, the theoretical possibility of terraforming Mars – that is, enacting global changes for the purpose of making it more able to sustain life similar to Earth – is an enchanting goal.

Just how to go about such an enormous feat is still in question.  Some hypothesize that by introducing bacteria or other microorganisms capable of surviving in the harsh environment the composition of the atmosphere could be gradually changed until larger and more human-friendly organisms like plants could be supported, in turn paving the way for insects or small animals.

Another possibility involves using massive mirror arrays in space or geothermal outlets on the surface to gradually warm the temperature of Mars to unlock greater quantities of life-giving water from the polar caps.

Regardless of the path chosen, even after researched and prototyped to perfection these processes would require investments of money, time and materials on a scale unfathomable to us today.  And there are still currently insurmountable challenges that could threaten the entire effort before it even begins: without a magnetosphere, what’s the point of enriching an atmosphere that the sun will only continue to blow away?  Is it worth terraforming a planet to support life on a world without any active mineral-recycling tectonic activity as we know it?

As early explorers, our job is to continue the hard work of the satellites and rovers (and the scientists and engineers who control them) to find the answers to these questions.  And even if we don’t get right to terraforming the planet, there is still plenty for us to do in preparation for future visitors.

So now with our sightseeing complete, the hard work begins.  The exploration of Mars means more to humankind than the opportunity to learn more about planetary formation and evolution.  It provides space and a safe (relatively speaking) environment for building our first habitats away from Earth.

Mars sits on the edge of the massive and dangerous asteroid belt.  Assuming humankind’s exploration of the solar system is only beginning, Mars could provide an important space for repairs and refuel for spacecraft heading farther out into the unknown.  Colonies – or entire cities, eventually – could be supported by mining, low-gravity manufacturing, and even tourism industries as the foundations we lay now continue to grow.  Just imagine the competitive sports scene on a world with 39% of the gravity of Earth!

Today’s episode has been an interesting view into the history and future of space exploration focused on Mars and the important place it holds for humankind.  We hope you’ve enjoyed our journey and look forward to continuing the adventure in our next episode!

Settle The Stars – Venus

Settle The Stars – Venus

Hello folks, this is Alexander Winn.  

In this episode we’ll be visiting Venus, our nearest neighbor and one of the most-watched objects in our sky throughout the ages.  In our journey we’ll learn about some of the strangest and fiercest conditions our Solar System has to offer: scorching heat, crushing pressure, dueling hurricanes and acid rain.  We’ll find out the latest in the search for alien life in this hellscape and learn about the pivotal role Venus has played in some of the most important discoveries in history and the important lessons she continues to teach us about our own home on Earth.

To us here on Earth, Venus is not some faraway, unknown world.  When we think about it, we don’t need some special mnemonic device as we would to remember the moons of Saturn or a special code designation like we use for the many comets buzzing around the Sun.  It’s right there in the sky, a familiar bright star clearly visible from just about everywhere on Earth.  In fact, before you even knew what a planet was, you might have even wished upon it with the popular poem: “Star light, star bright, first star I see tonight…”  As the brightest object in the sky after the Sun and Moon, it’s no wonder at all that Venus has captured our attention the way it has.  

Throughout history Venus has been a subject of interest and inspiration for us here on Earth.  Because Venus is closer to the Sun than us, it never strays far from it in the sky – which explains why it is visible in the morning or evening when the Sun is just below the horizon.  It also follows a synodic cycle in which the planet becomes invisible as it gets near the Sun, and then appears again on the opposite horizon on the other side of the Sun.  During this cycle, the planet can be observed quite high in the sky, but never quite reaches the apex.  These interesting features stirred the imaginations of early stargazers, who told stories about the gods and goddesses they attributed to Venus as a way to illustrate and explain these observations.

The disappearing act Venus plays, visible for a time in the morning and then switching to the evening as the planet passes Earth in its orbit, was of intense interest to many ancient cultures.  Many interpreted the phenomenon as an illustration of a god with two balanced aspects or explained the temporary disappearance (which lasted about three days) as a divine journey to the underworld.

The ancient Mesopotamians who lived where Iraq is today named the planet Inanna after the goddess of love and war – balanced aspects of life and death.  They recorded stories of Inanna’s journey into the underworld, her death and rebirth, to explain the disappearance of the planet from the sky.  In fact, many details of Inanna’s saga, from her journey to Kur, or the mountains of the West, to a heavenly search for her enemy can be linked to the movements of Venus in the sky.

Across the globe in Vietnam, ancient stargazers believed the morning star and evening star were two separate entities.  Folklore tells the story of two separated lover stars, sao Mai and sao Hôm, destined to search for each other and remain apart forever.

In classical Roman mythology, Venus was known as “Lucifer”, or “Light-Bringer” in Latin, in the morning and Vesper in the evening.  This mythology carried over into Christian stories of a fallen angel who was punished for attempting to climb too high within heaven, another link to Venus’ path which approaches – but never quite reaches – the apex of the sky.  Ancient myth about the planet was adopted elsewhere by Christians, appearing again in the book of Revelation, in which Jesus refers to himself as the “bright morning star”.  Interestingly, according to the story Jesus eventually undergoes his own three-day period of death and rebirth celebrated annually as Easter.

Perhaps no culture was as intensely devoted to Venus than the Mayans.  To the Mayans, Venus was known as Chac ek, “The Great Star”.  To the Mayans, Chak ek was the most important celestial body – even more so than the Sun and Moon.  Their calendars meticulously recorded the movement of the planet and predicted its activity over a period of thousands of years, accurate to within the hundredth part of a day.  The Mayans believed Chac ek influenced the activities and quality of life on Earth, and all major events within the empire – including war – were carefully timed to coincide with the position of the planet.

All these cultures and societies all over the world – too many to mention – were enthralled by this mysterious Morning Star and the mysterious order of her movement across the sky.  By observing, tracking and recording Venus and the other planets as meticulously as they did, a general understanding and appreciation emerged for astronomy.  This in turn advanced our understanding of the physics, optics, mathematics and geometry necessary to successfully observe the stars, leading to even more discoveries.

More recently, Venus contributed to Europe’s domination of the globe during the age of exploration.  Back in the 1700’s the seafaring nations were busy colonizing, waging war and trading all around the world.  But even with their new expertise and expensive warships, a seemingly simple question of navigation confounded them: How can a sailor accurately measure his location on the planet independently?   How far north or south of the equator a navigator is – or latitude – can be identified relatively easily by measuring the angle of the Sun at noon.  But identifying location longitudinally, or how far east or west one has travelled, is a much more difficult problem that led to some tragic and embarrassing shipwrecks at the time.

It was believed that having an exact measurement for all these relevant navigational references – the distance from Earth to the Sun, the distance to the planets, and the size of the Earth itself would contribute to a solution and provide an answer to the question of navigation.  And as it happened, a rare astronomical event – the transit of Venus – would provide an opportunity to provide that information.

The transit of Venus is the name for the special alignment of the Sun, Venus and Earth.  An observer here on Earth can witness Venus as it transits – or travels – across the face of the Sun.  Astronomers at the time realized that by timing the length of time it takes for Venus to pass between the Earth and Sun from various vantage points across the globe, all kinds of measurements could be calculated: the size of the Sun, Venus and Earth, for starters – as well as the distances between each of them.

The scientists realized they would only get two shots at this, because transits of Venus are a once-in-a-lifetime event.  The orbital cycles produce a pair of transits eight years apart about every century, so expeditions were prepared around the world in one of the first international scientific endeavors to record the transits in 1761 and 1768.

The transit of Venus in 1761 was an excellent trial run.  The expeditions included a new team of astronomer Charles Mason and surveyor Jeremiah Dixon, whose excellent observations would make them famous enough to be called to settle a land dispute in North America by establishing the historic Mason-Dixon Line.

But the second transit in 1768 was the main event, with observers sent from the arctic circle to the south Pacific.  A special scientific commission from King George III placed Lt. Captain James Cook in command of the Endeavor to lead the expedition to Tahiti.  After a successful observation of the transit from the southern islands, Captain Cook steered his ship westward to eventually reach the mythical Terra Australis Incognita and claim the continent now known as Australia for the British Empire.

So, we see how even as an object of curiosity and inquiry, Venus has played a major role in the shaping of our collective human history.  Major advances in the study of physics, astronomy and mathematics were made in our attempt to better understand the planet and how it related to our own.

Over the centuries as telescopes became more advanced we would observe that the entire planet is permanently engulfed in thick clouds, spurring imaginative theories and fictions of advanced civilizations living and breathing just like us.

Once we got a closer look with the help of satellites and probes, we realized how unlikely that was.  Since 1961, 42 missions have been attempted to explore Venus, with the first successful flyby in 1962 by NASA’s Mariner 2 probe.  The first ever successful human landing on another planet was achieved by the Soviet Venera 8 lander in 1972.  While the data returned from Venera 8 was limited, subsequent landings and flybys painted the picture of a planet far different from the beckoning and jubilant morning star celebrated by so many cultures around the world.

These early observations depicted a hellscape.  An atmosphere dense enough to crush a steel craft raged in a perpetual tempest at the poles, and where scientists hoped clouds might offer life-giving rain almost no trace of water was found.  Instead, corrosive sulfuric acid was found in abundance, with the toxic liquid actually raining down from the sky at higher altitudes.  And across every surface, infused in every gust of caustic wind, was an astonishingly intense heat.

It became clear that any life here would be having a rough time of it.  By the 1970s it was clear that complex life on the planet would not be viable, but scientific debate continues even today on whether the atmosphere might support colonies of extreme bacteria or similar organisms.  Evidence for life continues to be sought within the data and spectrophotometric data collected so far, but definitive confirmation will hopefully be provided by one of the 15 future missions currently being developed by various agencies worldwide.

So, what does all this mean for potential human exploration?  How would an explorer experience these conditions firsthand?  By compiling our observations so far we can make a rather good guess.

Step one for many explorers will probably be to say goodbye to friends and loved ones – doubly so for the first visitor to a world as dangerous as Venus.  Not necessarily because it is a suicide mission – scientists and engineers will do their best to keep you safe – but because early manned voyages probably won’t come with a return ticket.  Fuel and repairs are tough to come by without infrastructure, and the thick atmosphere of Venus will require an immense amount of thrust to relinquish any craft back to open space.  So, the first explorers will probably become permanent residents to pave the way for future visits.

Fortunately, Venus is close, a mere 24.8 million miles at its closest, but it’s never a straight shot between orbiting planets.  The quickest trip to Venus so far was accomplished by Mariner 2 in 1962 which spent 109 days en route.  It’s probably safe to assume a trip will take around 120 to 130 days, or 4 months.  In terms of space travel, that’s a quick commute.  If you manage a full night’s rest all along the way you’d be left with about 2,000 hours’ worth of time to kill.  Assuming any interplanetary explorer worth their salt is a fan of Star Wars, you’d have enough time to watch the full series of 11 live-action movies only 80 times or so before it was time to land.

But sadly, you probably wouldn’t get the chance to make it through that many.  Your waking hours will more likely be filled with exercise to keep your muscles and bones strong as they become accustomed to weightlessness, patching up the occasional damage caused by a stray piece of debris or conducting experiments to make future long-term space travel easier for future explorers.  So maybe you’d only get to see Star Wars 30 or 40 times.  Bummer, I know.  But the real work begins once Venus is in view.  

The first task will be determining a final position to bring the spacecraft in for landing.  Beneath the clouds the surface is generally rocky and uneven just about everywhere, so the main consideration will be weather.  The clouds will obscure your view of the sky anywhere on the planet, but the equator offers less wind which is no small concession.  As far from the poles as you can get is usually where you want to be on Venus.

Scientists were mystified to discover that both the north and south poles of Venus are crowned by intense storms unlike anything they’ve seen before.  At each pole swirls a violent double vortex, each of which churns like two hurricanes here on Earth circling around each other.  The south pole has been better observed, where the combined size of this huge storm is estimated to be as large as Europe with wind speeds of over 300 kilometers per hour.  Most of the wind at surface level is composed of carbon dioxide, which makes up 96.5% of the atmosphere, and most of the rest is nitrogen.  That means the air is much, much heavier than here on Earth – about 50 times as dense.  So, if 300 kilometer-an-hour winds doesn’t sound all that bad to you, remember that it packs a much heavier punch.

If it’s all the same to you, I suggest we land closer to the equator where wind speeds are usually down to about 5 km/hr.  Our landing module will be reinforced like a submarine to counter the intense pressure of the atmosphere as we descend.  Even just alighting atop a hill on the surface of Venus is the pressure equivalent of diving 3,000 feet underwater here on Earth.  Admittedly, most submarines on Earth aren’t bathed in sulfuric acid before they carry people deep underwater, but unfortunately there’s no way around it here on Venus.  The thick clouds covering the planet are almost entirely composed of the corrosive acid, so our lander will have to be well protected to ensure we continue to withstand the pressure and heat as we descend.  And boy, is it hot.  Venus has the hottest temperatures in the Solar System outside of the Sun, thanks to that thick blanket of clouds.  Our poor landing module will also need to protect us from temperatures hot enough to melt lead, around 880 degrees Fahrenheit (that’s 470 Celsius).  At least we won’t get zapped by lightning.  Probably.  The clouds do appear capable of producing lightning like on Earth, no strikes have been observed directly yet so if it does occur it’s likely pretty rare.  So that’s good.

But here we are at last, safe and sound on our own little slice of paradise – we survived the wind, the acid clouds, the scorching heat and the crushing pressure.  Now what?

I don’t think a little sightseeing would be out of the question, we did just travel quite a long way after all.  But if you’re waiting to see what a sunset looks like beneath the churning clouds of Venus, you might be waiting a while.  A single day on Venus is as long as 243 days on Earth – that’s the slowest rotation in our solar system by a long way.  And not that it will make much of a difference from under the acidic haze, but the Sun will actually set, very slowly, into the eastern horizon instead of the west.

There won’t be different seasons to speak of like we’re used to on Earth, so no need to plan a different outfit for the springtime – you’ll find your ultraprotective suit to be conveniently stylish year-round here.  A supercritical sea of carbon dioxide at ground level would probably make walking outside feel like you’re trudging along underwater, but at least the thick atmosphere will keep us as cozy as a pot in a kiln throughout the long night.  On second thought, it’s probably best to get back inside.

Safe within our surface submersible we can turn our attention to observation and experimentation, to attempt to unravel some of the other grand mysteries Venus still holds.

For starters, as we look up into the toxic, roiling clouds: how has the atmosphere changed into this incredibly hostile state?  There are a lot of unexpected peculiarities about Venus’ sky for us to consider, for example its composition – for being so similar to Earth in size, composition and location, the air of Venus is highly enriched with noble gasses as compared with Earth.  Does this hint that the planets formed from very different primordial nebula compositions, despite their proximity?  Or perhaps a large comet impact delivered the gasses in some past collision?  There are likely many clues to be found within the craters and rocks of the planet to help support or discount these theories.

What’s going on beneath our feet, anyway?  What lessons can we learn about volcanism and plate tectonics?  What evidence can we find beneath the clouds that are impossible for our telescopes and probes to see from above?  It is clear that volcanoes once covered the landscape – in fact, there are many times more volcanoes on the surface of Venus than Earth, and many of them are larger than the largest here on Earth.  But are any of them still active?  Perhaps this is explained by the fact that without the continuous recycling of crust that the Earth undergoes, the Venusian volcanoes simply last longer, shielded from erosion and impacts by the thick atmosphere?

Erosion does seem to work differently on Venus.  On the occasion that an object manages to punch through the thick Venusian clouds, it makes a crater just like you would expect.  On Earth, such craters are worn down by wind and rain, and on a world with no atmosphere the craters are gradually erased by… other craters.  But most of the craters on Venus appear to be in pristine condition.

Paired with the high number of well-preserved but quiet volcano calderas, these observations support a prominent theory that Venus underwent a globally catastrophic resurfacing event sometime around 300 to 600 million years ago.  Perhaps in contrast to Earth’s gigantic conveyor belts of crust being generated and subducted, Venus alternates between long periods of geologic calm, gradually building temperature and pressure until everything is released in a massive, planet-wide eruption.  Perhaps a quick escape pod would be a good idea after all…

And speaking of erosion, where has all the water gone?  With such an abundance on nearby Earth, surely there would be traces on our twin world.  One hint lies in one curious detail: Venus lacks a large internally generated magnetic field like the one Earth has.  Instead, it’s much weaker magnetic field is induced as an interaction between the outer ionosphere as it collides with the solar wind from the sun as opposed to an internal dynamo generated by convection currents in the mantle.  Not only is this more evidence that the internal workings of the planet differ from Earth’s, but also helps explain the lack of water: as the heat of Venus rose and water evaporated, it was gradually blown away by the solar wind without a protective magnetic field.

There are many differences between the Earth and Venus, but from the perspective of organisms living on a planet currently undergoing rapid climate change, the lessons from Venus are invaluable.  Evidence shows that in the past Venus was likely quite different, with global, permanent changes to the characteristics of the planet imposed by a drastic runaway greenhouse effect.  Whether the effect was initiated by some specific geologic event or gradually snowballed as a natural progression from its initial composition is still in question, but the very real and profoundly serious effects of these processes is well worth our study.  We could learn more about the forces at work in our environment on Earth, helping us prepare for new challenges or warning us of the catastrophic consequences of our actions.

To encourage future expeditions to the planet, it will fall to us as the first explorers on Venus to make sure the adventurers to follow find more comfort and access than our little shelter can provide.

One promising idea is to take advantage of the thick Venusian air and sail atop it in a great airship instead of sheltering on the surface.  A container of air as we would find it on Earth would be quite buoyant indeed on Venus, which has caused some engineers to envision entire colonies – or even cities – of humans floating above the clouds to continue study of the planet from above.

A valuable takeaway from our visit to Venus is that even after the dozens of successful probe and lander missions, centuries of observation from telescopes, an impressive array of sensors and massive amounts of data, our nearest and most similar neighbor still holds so many questions to be answered.  Next to the farthest and strangest space anomalies detectable from Earth, it can seem like the book on Venus has been written and closed already – but nothing could be further from the truth.

We hope you enjoyed our visit to our sister planet today and learned some interesting facts to feed your curiosity about this mysterious planet.  We’ll be continuing our journey next week to another familiar destination with another personal interplanetary tour – this time of the Red Planet, Mars.

Settle The Stars – Mercury: Turning Slowly, Moving Fast

Settle The Stars- Mercury: Turning Slowly, Moving Fast

Alexander Winn takes us to Mercury to discuss how… habitable it is.. or (spoiler alert) it isn’t.


Hey folks, this is Alexander Winn.  

In this episode we’ll be visiting Mercury, the fascinating small rocky world zipping around the Sun.  This will be the first in a series of episodes exploring the solar system and all the unique histories, challenges, and opportunities it includes, one planet at a time.

Mercury has captured the attention and imagination of stargazers for millennia, and today we’ll take a closer look at the mysteries and discoveries that continue to shape our understanding of this little planet.

Based on all the information accumulated, we can sketch out our likely observations as we make our own imaginary visit to the planet.

Planning the trip would have been slightly different from visiting other planets in the Solar System.  A route to Mercury must take into account its unique orbit, which is the most eccentric of all the planets.  That means that if you were to look at the orbit from above, you would notice it doesn’t follow a circular path around the Sun.  The actual orbital path looks more like an oval, with the Sun slightly off-center from the middle.  The result is that the distance between the Sun and Mercury can vary quite a bit, from 46 million kilometers to 70 million kilometers at opposite ends.

As we approach and enter Mercury’s orbit in preparation for landing, we would find the surface to look a lot like that of the Moon – heavily cratered and grey.  One crater is particularly striking, due to its massive size.  It’s called the Caloris Planitia and could comfortably fit the state of Texas.  This crater was caused by an impact so large that the terrain on the opposite side of the planet has also been altered – possibly by shockwaves traveling around the planet and converging on the other side.

There would be mountains and ridges as expected, but upon closer inspection we would notice what look like strange ripples and wrinkles in the landscape.  These are features first spotted by probes, and evidence that the planet is actually shrinking – albeit very slowly.  The radius of Mercury has decreased by about one to seven kilometers over time as the inside of the planet has cooled, leaving the outer crust to bunch up into these strange shapes.

In the past Mercury had a lively volcanic history.  As we peer out of our imaginary spacecraft we can still see some evidence of volcanic activity in the form of cooled lava flows in some locations, but now that the inside of the planet is cooler the volcanoes have stopped.

The inside of the planet has not cooled completely, though – surprisingly our ship’s magnetometer can tell us that right away.  Surrounding the planet is a strong and stable magnetic field.  This field is much like that on Earth in that it is dipolar and aligned with the rotational axis of the planet, but much weaker – only about 1.1% as strong as our own.  These magnetic fields have only been observed on planets with a liquid-hot, iron-rich core, which generates the field with what’s called a dynamo effect.

As we make our preparations for landing, one more striking feature becomes obvious to us: the planet is rotating very slowly.  One day on Mercury lasts 58 Earth days, and when you account for the quick time it takes to revolve around the Sun, the small planet completes three of its days every two Mercurian years.

Scientists have some of these observations – the slow rotation, the impact crater, the eccentric orbit, and strange terrain – linking them to a single impact event that has forever changed the planet.  There is evidence that the entire planet was once tidally locked in its orbit around the Sun, in the same way the Moon is tidally locked around the Earth.  The Moon orbits the Earth and rotates on its axis in an extremely stable arrangement in such a way that only one side of the Moon ever faces the Earth.  Similarly, for possibly billions of years Mercury only showed one face to the Sun.  

Scientists believe that an object at least 62 miles in diameter smashed into the planet, forming the massive crater and causing the slow rotation we observe today.

Once on the ground, our bodies begin to adjust once again to the presence of gravity.  We only weigh a bit more than 1/3 what we do on Earth, but our muscles, skeletons and sense of balance welcome the familiar feeling of solid ground underfoot.

Our imaginations and intuitions are mostly correct as we begin exploring Mercury.  It’s the closest planet to the Sun, so it must get pretty hot, right?  Absolutely, to the tune of 800 degrees Fahrenheit.  That’s over six times hotter than the highest temperature recorded on Earth, in Death Valley California – so double-check your spacesuit coolant.  And while you’re at it, check the heating mechanism too, because what is less obvious is that due to its extremely thin atmosphere, almost all this heat dissipates as the planet slowly rotates out of the sunlight.  The result is a long, cold night where temperatures can reach as low as -136 degrees Fahrenheit.  That’s the largest surface temperature discrepancy anywhere in the Solar System, and just more evidence that the climate on Mercury can be very… well, mercurial.

And not that you need reminding, but better keep that helmet on.  The atmosphere on Mercury is barely there and very transient, being replenished by evaporation and radioactive decay of elements on the surface of the planet just as quickly as its being blown away by the solar wind.  Certainly nowhere near breathable, let alone fly the space kite we brought.

If it isn’t obvious yet, Mercury is not very hospitable to human visitors.  It is much more comfortably observed from afar as we’ve enjoyed doing so far.

[History of Human Exploration]

Mercury is visible to the naked eye, so it’s been on the mind of astronomers on Earth for an awfully long time.  The first thing that probably stood out to early stargazers is that against a backdrop of stars that march across the sky in more or less the same formation, Mercury is one of only a handful of lights that follows a different path.  We know now that these independent bodies are in fact planets, but back then they were special stars – and deserved special names to designate their higher status.

It would be easy to assume that Mercury was named after the god of communication and commerce for obvious reasons.  It moves so quickly relative to the other stars, and it never moves far from the Sun in the sky, after all.  These are qualities we would expect the messenger for a king to have.  But it’s actually likely that the god Mercury (and similar gods in other cultures around the world) only exist because of the planet.  Without the unique qualities providing inspiration, perhaps there wouldn’t be a messenger god in the pantheon at all.

Whatever the reason the name has stuck, and it’s very appropriate.  We say that things are “mercurial” when they change quickly, which perfectly exemplifies the small planet’s quick movement around the Sun and drastic surface temperature changes.  But quick as it is, Mercury was spotted and recognized well before the Romans got around to naming it.

The ancient Greeks actually applied two different names to the planet originally.  It was called Hermes when the planet was visible in the evening after sunset, and Apollo when visible in the morning before sunrise.  Eventually Hermes stuck for both as it became clear the two were the same object, which the Romans adopted as Mercury.

Ancient Babylonians attributed similar divine qualities to the planet, naming it Nabu after the god of writing and divine messages.  The Babylonians also attributed both male and female aspects to the planet because of its appearance as both a morning and evening star.

Cultures around the world have watched Mercury closely for centuries, often linking its movements, characteristics and even mythology with that of Venus.  Because these two planets are both closer to the Sun than Earth, they follow a different pattern across the sky than the rest.  Being closer to the Sun also means they both exhibit phases when viewed from Earth, like our Moon.

Being closer to the Sun from Earth also means that from here we’re able to observe an event called the “transit” of each planet, which is when the planet passes between the Earth and the Sun.  Mechanically it’s like a solar eclipse, except that because Mercury is so much farther away from us from the Moon it doesn’t block as much light from the Sun.  You wouldn’t even notice it happening if you weren’t looking at the Sun, but these events fascinated early astronomers as they were valuable opportunities to estimate the size and distance of objects within the Solar System with a little help from geometry.  

Transits of Mercury are quite frequent given the speed of the small planet’s orbit, but much rarer are events called “occultations”.  These occur when multiple planets align perfectly in their orbits with Earth, and astronomers in 1737 were delighted to observe the occultation of Mercury and Venus from the Royal Observatory at Greenwich.  The same event won’t happen again until December 3, 2133.

Mercury’s closeness to the Sun and tiny size makes it quite difficult to observe from Earth, so it was only a matter of time before we tried getting right up close for a look.  But of course, being near the Sun also presents unique challenges to probes and spacecraft as well.  For starters, there is less room for navigational errors.  In wider space adjustments are easy to make with small thrusters.  But when targeting a small object so close to the Sun, high speeds and proximity to the star mean that one wrong move could send your expensive probe right into the Sun.  Of course, radiation and temperatures threaten to fry the delicate instruments and electronics as well.

But as you might expect, those challenges haven’t been enough to dissuade us from taking a shot at a valuable up-close look at Mercury.

In the mid-1970’s, Mariner 10 made the first fly-by of the planet and provided an unprecedented view of the planet’s geological features and discovered the planet-wide magnetic field.  The field was a big shock to everyone at home.  Mercury’s slow rotation was though to be a sure indicator of a geologically dead planet incapable of generating such a field, but in fact the field is structured and behaves similar to our own and helps shield the planet from some of the bombardment of solar radiation.  Mariner 10 shut down after making three close passes to the planet and – barring an unlikely collision with a space rock – could still be out there orbiting the Sun, occasionally passing by Mercury again for a quiet visit.

In 2005, we got our second chance to view Mercury with updated equipment.  NASA’s satellite MESSENGER was equipped with an array of instruments to capture more data about the planet over a year-long observation.  Scientists were eager to see more of Mercury’s surface and find out more about the geological history, search for water, and puzzle out how it can maintain even a sparse atmosphere.  We discovered that there is in fact water on the surface of Mercury, locked in ice deep in craters and crevices away from the sunlight.  MESSENGER completed its mission successfully on April 24, 2015 and went out with a bang – leaving a 52-foot crater as it fell to the surface.

[Future Human Exploration]

The future of Mercury is bright – please pardon the pun.  In 2018, the European Space Agency and the Japanese Space Agency joined together to launch BepiColombo, a new mission to probe the planet and discover even more.  When it reaches Mercury in 2025 it will spend a year studying the magnetic fields and capturing a variety of new infrared, ultraviolet, X-ray and gamma ray images of the surface to answer some of the biggest questions we have about the planet.  As is normal for all scientific ventures, hopefully these new observations will lead to even more questions, more missions, and more discoveries in the future.


Building on the contributions and careful observations of astronomers for centuries, we’ve collected a huge amount of information about one of the most mysterious and unusual planets in our Solar System.  I hope you enjoyed learning about Mercury, and I look forward to continuing our voyage across the stars in upcoming episodes.

In the meantime, be sure to subscribe if you haven’t already. Settle the Stars is available on pretty much every podcasting platform, and we’re also mirroring our episodes on YouTube at (and be sure to ring that bell so you know when there’s a new episode). And don’t miss the other awesome shows that are part of the Edgeworks Nebula: Slice of Science, the Synthesis, and our upcoming show You Have My Sword, where Krysti Pryde will be analyzing and deep-diving into the world of Lord of the Rings and JRR Tolkien’s Middle-earth.

Thank you all for listening, and as always, happy terraforming.

Settle the Stars is a proud member of the Edgeworks Nebula, a collection of intriguing and informative podcasts from Edgeworks Entertainment.