Venus: Death of a Planet

From the fires of a sun’s birth, twin planets emerged. Venus and Earth. Two roads diverged in our young solar system. Nature draped one world in the greens and blues of life. While enveloping the other in acid clouds, high heat, and volcanic flows. Why did Venus take such a disastrous turn? And what light can Earth’s sister planet shed on the search for other worlds like our own? For as long as we have gazed upon the stars, they have offered few signs that somewhere out there are worlds as rich and diverse as our own. Recently, though, astronomers have found ways to see into the bright lights of nearby stars. They’ve been discovering planets at a rapid clip, using orbiting observatories like NASA’s Kepler space telescope, and an array of ground-based instruments. The count is almost a thousand and rising. These alien worlds run the gamut, from great gas giants many times the size of our Jupiter, to rocky, charred remnants that burned when their parent star exploded. Some have wild elliptical orbits, swinging far out into space, then diving into scorching stellar winds.

Still others orbit so close to their parent stars that their surfaces are likely bathed in molten rock. Amid these hostile realms, a few bear tantalizing hints of water or ice, ingredients needed to nurture life as we know it. The race to find other Earths has raised anew the ancient question, whether, out in the folds of our galaxy, planets like our own are abundant, and life commonplace? Or whether Earth is a rare Garden of Eden in a barren universe? With so little direct evidence of these other worlds to go on, we have only the stories of planets within our own solar system to gauge the chances of finding another Earth. Consider, for example, a world that has long had the look and feel of a life-bearing planet. Except for the moon, there’s no brighter light in our night skies than the planet Venus, known as both the morning and the evening star. The ancient Romans named it for their goddess of beauty and love. In time, the master painters transformed this classical symbol into an erotic figure, then a courtesan.

It was a scientist, Galileo Galilei, who demystified planet Venus, charting its phases as it moved around the sun, drawing it into the ranks of the other planets. With a similar size and weight, Venus became known as Earth’s sister planet. But how Earth-like is it? The Russian scientist Mikkhail Lomonosov caught a tantalizing hint in 1761. As Venus passed in front of the Sun, he witnessed a hair thin luminescence on its edge. Venus, he found, has an atmosphere. Later observations revealed a thick layer of clouds. Astronomers imagined they were made of water vapor, like those on Earth. Did they obscure stormy, wet conditions below? And did anyone, or anything, live there? The answer came aboard an unlikely messenger, an asteroid that crashed into Earth.

That is, according to the classic sci-fi adventure, “The First Spaceship on Venus.“ A mysterious computer disk is found among the rubble. With anticipation rising on Earth, an international crew sets off to find out who sent it, and why. What they find is a treacherous, toxic world. No wonder the Venusians want to switch planets. It was now time to get serious about exploring our sister planet. NASA sent Mariner 2 to Venus in 1962, in the first-ever close planetary encounter. Its instruments showed that Venus is nothing at all like Earth. Rather, it’s extremely hot, with an atmosphere made up mostly of carbon dioxide. The data showed that Venus rotates very slowly, only once every 243 Earth days, and it goes in the opposite direction. American and Soviet scientists found out just how strange Venus is when they sent a series of landers down to take direct readings. Surface temperatures are almost 900 degrees Fahrenheit, hot enough to melt lead, with the air pressure 90 times higher than at sea level on Earth.

The air is so thick that it’s not a gas, but a “supercritical fluid.” Liquid CO2. On our planet, the only naturally occurring source is in the high-temperature, high-pressure environments of undersea volcanoes. The Soviet Venera landers sent back pictures showing that Venus is a vast garden of rock, with no water in sight. In fact, if you were to smooth out the surface of Venus, all the water in the atmosphere would be just 3 centimeters deep. Compare that to Earth, where the oceans would form a layer 3 kilometers deep. If you could land on Venus, you’d be treated to tranquil vistas and sunset skies, painted in orange hues. The winds are light, only a few miles per hour, but the air is so thick that a breeze would knock you over. Look up and you’d see fast-moving clouds, streaking around the planet at 300 kilometers per hour. These clouds form a dense high-altitude layer, from 45 to 66 kilometers above the surface. The clouds are so dense and reflective that Venus absorbs much less solar energy than Earth, even though it’s 30% closer to the Sun. These clouds curve around into a pair of immense planetary hurricanes as the air spirals down into the cooler polar regions.

Along the equator, they rise in powerful storms, unleashing bolts of lightning. Just like earth, these storms produce rain, only it’s acid rain that evaporates before it hits the ground. At higher elevations, a fine mist forms, not of water but of the rare metal tellurium, and iron pyrites, known as fool’s gold. It can form a metallic frost, like snowflakes in hell. Scientists have identified around 1700 major volcanic centers on Venus ranging from lava domes, and strange features called arachnoids or coronae, to giant volcanic summits. The planet is peppered with volcanoes, perhaps in the millions, distributed randomly on its surface. Venus is run through with huge cuts thousands of kilometers long that may well be lava channels. Our sister planet is a volcanic paradise, in a solar system shaped by volcanism. The largest mountain on Earth, Hawaii’s Mauna Kea volcano, measures 32,000 feet from sea floor to summit.

Rising almost three times higher is the mother of all volcanoes: Olympus Mons on Mars. Jupiter’s moon Io, is bleeding lava. It’s produced deep underground by the friction of rock on rock, caused by the gravitational pull of its mother planet. Then there’s Neptune’s moon Triton, with crystals of nitrogen ice shooting some 10 kilometers above the surface. Saturn’s moon Titan, with frozen liquid methane and ammonia oozing into lakes and swamps. On our planet, volcanoes commonly form at the margins of continents and oceans. Here, the vast slabs of rock that underlie the oceans push beneath those that bear the continents. Deep underground, magma mixes with water, and the rising pressure forces it up in explosive eruptions. On Venus, the scene is very different. In the high-density atmosphere, volcanoes are more likely to ooze and splatter, sending rivers of lava flowing down onto the lowlands. They resemble volcanoes that form at hot spots like the Hawaiian islands.

There, plumes of magma rise up from deep within the earth, releasing the pressure in a stream of eruptions. To see a typical large volcano on Venus, go to Sappas Mons, at 400 kilometers across and 1.5 kilometers high. The mountain was likely built through eruptions at its summit. But as magma reached up from below, it began to drain out through subsurface tubes or cracks that formed a web of channels leading onto the surrounding terrain. Is Venus, like Earth, still volcanically active? Finding the answer is a major goal of the Venus Express mission, launched in 2005 by the European Space Agency. Armed with a new generation of high-tech sensors, it peered through the clouds. Recording the infrared light given off by several large mountains, it found that the summits are brighter than the surrounding basins. That’s probably because they had not been subject to as much weathering in this corrosive environment.

This means that they would have erupted sometime within the last few hundred thousand years. If these volcanoes are active now, it’s because they are part of a deeper process that shapes our planet as well. On Earth, the release of heat from radioactive decay deep in its mantle is what drives the motion of oceanic and continental plates. It’s dependent on erosion and other processes associated with water. With no water on Venus, the planet’s internal heat builds to extreme levels, then escapes in outbreaks of volcanism that may be global in scope. This may explain why fewer than a thousand impact craters have been found on Venus. Anything older than about 500 million years has literally been paved over. So why did Venus diverge so radically from Earth when it was born in same solar system and under similar circumstances? There is growing evidence, still circumstantial, that Venus may in fact have had a wetter, more Earth-like past.

One of the most startling findings of the early Venus missions was the presence of deuterium, a form of hydrogen, in Venus’ upper atmosphere. It forms when ultraviolet sunlight breaks apart water molecules. Additional evidence recently came to light. Venus Express trained its infrared sensors on the planet’s night side, to look at how the terrain emits the energy captured in the heat of the day. This picture is a composite of over a thousand individual images of Venus’ southern hemisphere. Higher elevation areas, shown in blue, emit less heat than the surrounding basins. That supports a hypothesis that these areas are made not of lava, but of granite. On Earth, granite forms in volcanoes when magma mixes with water. If there’s granite on Venus, then there may well have been water. If Earth and Venus emerged together as twin blue marbles, then at some point, the two worlds parted company.

Earth developed ways to moderate its climate, in part by removing carbon dioxide, a greenhouse gas, from its atmos phere. Plants, for one, absorb CO2 and release oxygen in photosynthesis. One square kilometer of tropical jungle, for example, can take in several hundred tons of co2 in just a year. That’s nothing compared to the oceans. In a year’s time, according to one recent study, just one square kilometer of ocean can absorb 41 million tons of CO2. Earth takes in its own share of CO2. When rainfall interacts with rocks, a chemical reaction known as “weathering” converts atmospheric CO2 to carbonate compounds. Runoff from the land washes it into rivers and the seas, where they settle into ocean sediments. With little water and no oceans, Venus has no good way to remove CO2 from its atmosphere. Instead, with volcanic eruptions adding more and more CO2 to the atmosphere, it has trapped more and more of the sun’s heat in a runaway greenhouse effect. Venus is so hot that liquid water simply cannot survive on the surface. Nor, it seems, can it last in the upper atmosphere.

The culprit is the Sun. The outer reaches of its atmosphere, the corona, is made up of plasma heated to over a million degrees Celsius. From this region, the sun sends a steady stream of charged particles racing out into the solar system. The solar wind reaches its peak in the wake of great looping eruptions on the surface of the Sun, called coronal mass ejections. The blast wave sweeps by Venus, then heads out toward Earth. Our planet is fortified against the solar blast. Plumes of hot magma rise and fall in Earth’s core as it spins, generating a magnetic field that extends far out into space. It acts as a shield, deflecting the solar wind and causing it to flow past. It’s this protective bubble that Venus lacks. Venus Express found that these solar winds are steadily stripping off lighter molecules of hydrogen and oxygen.

They escape the planet on the night side, then ride solar breezes on out into space. All this may be due to Venus’ size, 80% that of Earth. This prevents the formation of a solid iron core, and with it the rising and falling plumes that generate a strong magnetic field. There may be another reason too, according to a theory about the planet’s early years. A young planet Venus encountered one or more planet-sized objects, in violent collisions. The force of these impacts slowed its rotation to a crawl, and reversed it, reducing the chances that a magnetic field could take hold. This theory may have a surprising bearing on Earth’s own history. Scientists believe the sun was not always as hot as it is. In fact, going back several billion years, it was cool enough that Earth should have been frozen over. Because it was not, this is known as the faint young sun paradox. Earth’s salvation may well be linked to Venus’ fate.

The idea is that the Earth occupied an orbit closer to the Sun, allowing it to capture more heat. The gravity of two smaller planets with unstable orbits would have gradually pushed it out to its present orbit. The pair would eventually come together, merging to form the Venus we know. As dead as Venus is today, it has brought surprising dividends in the search for life. On its recent crossing between Earth and the Sun, astronomers were out in force. In remote locations where the viewing was optimal, such as the Svalbard islands north of Norway. The data gathered here would be added to that collected by solar telescopes on the ground and in space. To object for most was to experience a spectacle that will not occur again till the year 2117. It was also to capture sunlight passing through Venus’ atmosphere.

Today, the Kepler Space Telescope is searching for planets around distant stars by detecting dips in their light as a planet passes in front. Telescopes in the future may be able to analyze the light of the planet itself. If elements such as carbon or oxygen are detected, then these worlds may well be “Earth-like.” Venus provides a benchmark, and some valuable perspective. So what can we glean from the evolution of planet Venus? As we continue to scan the cosmic horizons, the story of Venus will stand as a stark reminder. It takes more than just the right size, composition, and distance from the parent star, for a planet to become truly Earth-like. No matter how promising a planet may be, there are myriad forces out there that can radically alter its course. For here was a world, Venus, poised perhaps on the brink of a glorious future.

But bad luck passed its way. Now, we can only imagine what might have become of Earth’s sister planet? 8.

Unstoppable Solar Cycles – Debate

LEGATES: The one thing I've learned over about 30 years of study of the climate has been it's a very complicated system. We like to simplify it for discussion with students, with laypersons, but it's really a very complicated system. BETH: This is the challenge. Do we really understand what’s happening? We are urged to accept just one theory — that human-generated CO2 is the principal cause of global warming. Yet these and other scientists point to other possible causes. The journal Physics and Society, which is a publication of The American Physical Society with a membership of over 50,000 physicists, now welcomes debate of the question. (Music) Scientists are also expressing concern about the distortion of the science. (Music) SOON: Those views are indeed promoted by political bodies which is the Intergovernmental Panel for Climate Change. And there appears to be a corrupted process, in my opinion, of the bodies. LEGATES: There’s a science document which is really written by scientists, for scientists. There’s also a summary for policymakers.

It’s put together by policymakers and in many cases they go back to the scientists and say, “Can you change the science document to match our summary? We want to beef this up. We want to make it look worse.” That’s not the way science is done. SOON: I think science and scientists are being misused in a lot of ways. And these are all becoming really the war of words instead of war of evidence and science. That troubles me. LEGATES: So the idea of science is you're really supposed to be skeptical. So there's always a quest to verify what we know, to understand that we haven't made a mistake and that we continue on and develop science. If we've closed our minds – if we close the doors – we are now shutting ourselves out from the real truth which is what science is all about after all..

Earth in 1000 Years

Ice in its varied forms covers as much as 16% of Earth’s surface, including 33% of land areas at the height of the northern winter. Glaciers, sea ice, permafrost, ice sheets and snow play an important role in Earth’s climate. They reflect energy back to space, shape ocean currents, and spawn weather patterns. But there are signs that Earth’s great stores of ice are beginning to melt. To find out where Earth might be headed, scientists are drilling down into the ice, and scouring ancient sea beds, for evidence of past climate change. What are they learning about the fate of our planet, a thousand years into the future and even beyond? 30,000 years ago, Earth began a relentless descent into winter, Glaciers pushed into what were temperate zones. Ice spread beyond polar seas. New layers of ice accumulated on the vast frozen plateau of Greenland.

At three kilometers thick, Greenland’s ice sheet is a monumental formation built over successive ice ages and millions of years. It’s so heavy that it has pushed much of the island down below sea level. And yet, today, scientists have begun to wonder how resilient this ice sheet really is. Average global temperatures have risen about one degree Celsius since the industrial revolution. They could go up another degree by the end of this century. If Greenland’s ice sheet were to melt, sea levels would rise by over seven meters. That would destroy or threaten the homes and livelihoods of up to a quarter of the world’s population. These elevation maps show some of the areas at risk. Black and red are less than 10 meters above current sea level. The Southeastern United States, including Florida, And Louisiana.

Bangladesh. The Persian Gulf. Parts of Southeast Asia and China. That’s just the beginning. With so much at stake, scientists are monitoring Earth’s frozen zones, with satellites, radar flights, and expeditions to drill deep into ice sheets. And they are reconstructing past climates, looking for clues to where Earth might now be headed, not just centuries, but thousands of years in the future. Periods of melting and freezing, it turns out, are central events in our planet’s history. That’s been born out by evidence ranging from geological traces of past sea levels, the distribution of fossils, chemical traces that correspond to ocean temperatures, and more. Going back over two billion years, earth has experienced five major glacial or ice ages. The first, called the Huronian, has been linked to the rise of photosynthesis in primitive organisms. They began to take in carbon dioxide, an important greenhouse gas. That decreased the amount of solar energy trapped by the atmosphere, sending Earth into a deep freeze.

The second major ice age began 580 million years ago. It was so severe, it’s often referred to as “snowball earth.” The Andean-Saharan and the Karoo ice ages began 460 and 360 million years ago. Finally, there’s the Quaternary, from 2.6 million years ago to the present. Periods of cooling and warming have been spurred by a range of interlocking factors: volcanic events, the evolution of plants and animals, patterns of ocean circulation, the movement of continents. The world as we know it was beginning to take shape in the period from 90 to 50 million years ago. The continents were moving toward their present positions. The Americas separated from Europe and Africa. India headed toward a merger with Asia. The world was getting warmer.

Temperatures spiked roughly 55 million years ago, going up about 5 degrees Celsius in just a few thousand years. CO2 levels rose to about 1000 parts per million, compared to 280 in pre-industrial times, and 390 today. But the stage was set for a major cool down. The configuration of landmasses had cut the Arctic off from the wider oceans. That allowed a layer of fresh water to settle over it, and a sea plant called Azolla to spread widely. In a year, it can soak up as much as 6 tons of CO2 per acre. Plowing into Asia, the Indian subcontinent caused the mighty Himalayan Mountains to rise up. In a process called weathering, rainfall interacting with exposed rock began to draw more CO2 from the atmosphere, washing it into the sea. Temperatures steadily dropped.

By around 33 million years ago, South America had separated from Antarctica. Currents swirling around the continent isolated it from warm waters to the north. An ice sheet formed. In time, with temperatures and CO2 levels continuing to fall, the door was open for a more subtle climate driver. It was first described by the 19th century Serbian scientist, Milutin Milankovic. He saw that periodic variations in Earth’s rotational motion altered the amount of solar radiation striking the poles. In combination, every 100,000 years or so, these variations have sent earth into a period of cool temperatures and spreading ice. Each glacial period was followed by an interglacial period in which temperatures rose and the ice retreated. The Milankovic cycles are not strong enough by themselves to cause the shift.

What they do is get the ball rolling. A decrease in solar energy hitting the Arctic allows sea ice to form in winter and remain over summer, then to expand its reach the following year. The ice reflects more solar energy back to space. A colder ocean stores more CO2, which further dampens the greenhouse effect. Conversely, when ocean temperatures rise, more CO2 escapes into the atmosphere, where it traps more solar energy. With so many factors at play, each swing of the climate pendulum has produced its own unique conditions. Take, for example, the last interglacial, known as the Eemian, from 130 to 115,000 years ago. This happened at a time when CO2 was at preindustrial levels, and global temperatures had risen only modestly. But with higher solar energy striking the north, temperatures rose dramatically in the Arctic. The effect was amplified by the lower reflectivity of ice-free seas and spreading northern forests.

There is still uncertainty about how much these changes affected sea levels. Estimates range from a 5 to 9 meters, levels that would be catastrophic today. That’s one reason scientists today are intensively monitoring Earth’s frozen zones, including the ice sheet that covers Greenland. Satellite radar shows the flow of ice from the interior of the island and into glaciers. In the eastern part of the island, glaciers push slowly through complex coastal terrain. In areas of higher snowfall in the northwest and west, the ice speeds up by a factor 10. The landscape channels the ice into many small glaciers that flow straight down to the sea. In the distant past, the center of the island may have been drained by a giant canyon, recently discovered. Scientists found that it’s 550 kilometers long and up to 800 meters deep.

It leads from Greenland’s interior to one of today’s most volatile glaciers. This is the Petermann Glacier in Northwest Greenland. Amid unusually warm summer temperatures in 2012, satellites tracked a giant iceberg as it broke off and moved down the glacier’s outlet channel. At about 31 square kilometers, this island of ice stayed together as it floated along. After two months, it finally began to fragment. The Jakobshavn glacier on Greenland’s west coast flows toward the sea at a rapid rate of 20 to 40 meters per day. At the ice front, where the glacier meets the sea, Jakobshavn has been retreating as it dumps more and more ice into the ocean. You can see it in this map. In 1851, the front was down here. Now it’s 50 kilometers up. One reason, scientists say, is that water seeping down into its base is acting like a lubricant.

Another is that as the glacier thins, it’s more likely to break off, or calve, when it interacts with warmer ocean waters. Scientists are tracking the overall rate of ice loss with the Grace Satellite. They found that from 2003 to 2009, Greenland lost about a trillion tons, mostly along its coastlines. This number mirrors ice loss in the Arctic as a whole. By 2012, summer sea ice coverage had fallen to a little more than half of what it was in the year 1980. While the ice rebounded in 2013, the coverage was still well below the average of the last three decades. Analyzing global data from Grace, one study reports that Earth lost about 4,000 cubic kilometers of ice in the decade leading up to 2012. Sea levels around the world are now expected to rise about a meter by the end of the century. What will happen beyond that? To gauge the resilience of Greenland’s great ice sheet, scientists mounted one of the most intensive glacial drilling projects to date, the North Greenland Eemian Ice Drilling Project, or NEEM. The ice samples they obtained from the height of Eemian warming told a surprising story.

If you were a visitor to Northern Greenland in those times, you would have stood on ice over two kilometers thick. Temperatures were warmer than today by about 8 degrees Celsius. And yet, the ice had receded by only about 25%, a relatively modest amount. That has shifted the focus to Earth’s other, much larger ice sheet, on the continent of Antarctica. Antarctica contains 90% of all the ice, and 70% of all the fresh water on the Earth. Scientists are asking: how dynamic are its ice sheets? How sensitive are they to melting? Data from Grace and other satellites shows that this frozen continent overall has lately been losing as much ice as it gains. The vast plateau of Antarctic ice is one of the driest deserts on Earth. What little snow falls, remains, adding to the continent’s mass. You can see evidence of this in the snow and ice that piles up at the South Pole research station. This geodesic dome was built in the 1970s.

By the time it was decommissioned in 2009, the entrance was nearly buried. With a thickness of up to 4 kilometers, the ice on which this outpost sits will not melt easily. That’s true in part because of the landmass below it, captured in an extraordinary radar image. The eastern part of the continent, the far side of the image, is a stable foundation of continental crust. In contrast, the western side dips as much as 2500 meters below present day sea level. Along the Amundsen Sea Coast, the ice is disappearing at an accelerating rate. Inland ice streams are moving toward the ocean at at least 100 meters per year. They end up in floating ice shelves that extend hundreds of miles into the ocean. This region is the greatest source of uncertainty about global sea level projections. When ice shelves like this grow, they become prone to fracturing. A giant crack, for example, recently appeared in the Pine Island Glacier. Within two years, a 720 square kilometer iceberg had broken off.

But the scientists are more concerned about what’s happening below the surface. In recent times, the Southern ocean that swirls around the continent has been getting warmer, at the rate of .2 degrees Celsius per decade. That has affected ice shelves like Pine Island by melting them from below. In a comprehensive survey of the continent, scientists concluded that this process was responsible for 55 percent of the mass lost from ice shelves between 2003 and 2008. It’s also been blamed for one of the more puzzling twists in the story of climate change, the spread of sea ice all around Antarctica. One possibility is that ramped up winds, circling the pole, are pushing the ice into thicker, more resilient formations. Another is that the melting of ice shelves has spread a layer of cold, fresh water over coastal seas, which readily freezes.

A team of researchers has come to the Pine Island Glacier to try to monitor the melting in real time. After five years of preparation, they drilled through 500 meters of ice to begin measuring ice volume, temperature, salinity, and flow. In some places, they found melt rates of about 6 centimeters per day, or about 22 meters in a year. Because ice shelves hold back inland glaciers, the melting could trigger larger changes. That’s likely what happened to the Larsen ice shelf on the Antarctic Peninsula in the year 2002. It’s thought to have been stable since the last interglacial. Warmer ocean waters had been eating away at Larsen’s underside. By early February of 2002, the shelf began to splinter into countless small icebergs. By March 7th, when this picture was taken, it had completely collapsed, forming a vast slush that drifted out to sea. Without the shelf’s buttressing effect, a series of nearby glaciers picked up speed, dumping an additional 27 cubic kilometers of ice into the ocean per year.

Evidence from the last interglacial, the Eemian, brings an ominous warning of what could lie ahead. It’s based on the height of ancient coral reefs, which grow to a depth relative to the sea level above them. Based on reefs along the Australian coast, a recent study published in the journal Nature showed that sea levels remained stable for most of the Eemian, at 3-4 meters above those of today. But the authors found that in the last few thousand years of the period, starting around 118,000 years ago, sea levels suddenly shot up to 9 meters above today. The authors concluded, in their words, that “a critical ice sheet stability threshold was crossed, resulting in the catastrophic collapse of polar ice sheets.” Looking ahead, uncertainties about the future of our climate abound. According to one study, the long cool down to the next glacial period is due to start in the next 1500 years or so, based on the timing of Milankovic cycles. But for this actually to happen, the study says, enough new ice would have to form to get the ball rolling. CO2 would have to retreat to below pre-industrial levels.

Instead, it appears that a warming climate is becoming a fact of life. The danger is that if the melting gains a momentum of its own, even reducing CO2 emissions may not be enough to stop it. The still unfolding story of Earth’s past tells us about the mechanisms that can shape our climate. But it’s the unique conditions of our time that will determine sea levels, ice coverage, and temperatures. What’s at stake in the coming centuries is the world we know, the one that has nurtured and sustained us. The Earth itself will go on, ever changing on short and long time scales, a dynamic living planet 1.