Artist's impression of the terraforming of Mars, from its current state to a livable world. Credit: Daein Ballard
The idea of terraforming Mars, making its atmosphere and environment more Earth-like for human settlement, goes back decades. During that time, many proposed methods have been considered and put aside as “too expensive” or requiring technology well in advance of what we have today. Nevertheless, the idea has persisted and is often considered a part of long-term plans for establishing a human presence on Mars. Given the many plans to establish human outposts on the Moon and then use that infrastructure to send missions to Mars, opportunities for terraforming may be closer than we think.
Unfortunately, any plans for terraforming Mars suffer from unresolved hurdles, not the least of which are the expense, distance, and the need for technologies that don’t currently exist. Triggering a greenhouse effect and warming the surface of Mars would take massive amounts of greenhouse gases, which would be very difficult and expensive to transport. However, a team of engineers and geophysicists led by the University of Chicago proposed a new method for terraforming Mars with nanoparticles. This method would take advantage of resources already present on the Martian surface and, according to their feasibility study, would be enough to start the terraforming process.
During the 1960s, the first robotic explorers began making flybys of Venus, including the Soviet Venera 1 and the Mariner 2 probes. These missions dispelled the popular myth that Venus was shrouded by dense rain clouds and had a tropical environment. Instead, these and subsequent missions revealed an extremely dense atmosphere predominantly composed of carbon dioxide. The few Venera landers that made it to the surface also confirmed that Venus is the hottest planet in the Solar System, with average temperatures of 464 °C (867 °F).
These findings drew attention to anthropogenic climate change and the possibility that something similar could happen on Earth. In a recent study, a team of astronomers from the University of Geneva (UNIGE) created the world’s first simulation of the entire greenhouse process that can turn a temperate planet suitable for Life into a hellish, hostile one. Their findings revealed that on Earth, a global average temperature rise of just a few tens of degrees (coupled with a slight rise in the Sun’s luminosity) would be sufficient to initiate this phenomenon and render our planet uninhabitable.
Venus has been garnering a lot of attention lately, though primarily in the scientific community as the last Hollywood movie about the planet was released in the 1960s. This is in part due to its dramatic difference from Earth, and what that difference might mean for the study of exoplanets. If we can better understand what happened during Venus’ formation to make it the hell scape it is today, we might be able to better understand what truly constitutes the habitable zone around other stars.
Numerous planetary scientists have focused on Venus’ formation and atmospheric development in the recent past. Now a new paper posits that Venus might have had liquid water on its surface as recently as one billion years ago. And a contributor to the disappearance of that water might be an unlikely culprit: Jupiter.
In Earth's atmosphere, CO2 lets sunlight in, but traps it in the atmosphere, warming the planet. The same thing, sort of, happens on Mars, where all the CO2 is frozen. Polar ice caps on Mars are a combination of water ice and frozen CO2. Just like its gaseous form here on Earth, frozen CO2 allows sunlight to penetrate while trapping heat. In the summer, this solid-state greenhouse effect creates pockets of warming under the ice, seen here as black dots in the ice. Image Credit: NASA
The idea of somehow terra-forming Mars to make it more habitable is a visionary, sci-fi dream. But though global terra-forming of Mars is out of reach, the idea persists. But now, a material called silica aerogel might make make the whole idea of terra-forming Mars slightly less impossible.
Observations suggest Venus may have had water oceans in its distant past. A land-ocean pattern like that above was used in a climate model to show how storm clouds could have shielded ancient Venus from strong sunlight and made the planet habitable. Credits: NASA
There’s no sense in sugar-coating it – Venus is a hellish place! It is the hottest planet in the Solar System, with atmospheric temperatures that are hot enough to melt lead. The air is also a toxic plume, composed predominantly of carbon dioxide and sulfuric acid rain clouds. And yet, scientists theorize that Venus was once a much different place, with a cooler atmosphere and liquid oceans on its surface.
Unfortunately, this all changed billions of years ago as Venus experienced a runaway greenhouse effect, changing the landscape into the hellish world we know today. According to a NASA-supported study by an international team of scientists, it may have actually been the presence of this ocean that caused Venus to experience this transition in the first place.
Artist's conception of a terraformed Mars. Credit: Ittiz/Wikimedia Commons
For almost a century now, the concept of terraforming has been explored at length by both science fiction writers and scientists alike. Much like setting foot on another planet or traveling to the nearest star, the idea of altering an uninhabitable planet to make it suitable for humans is a dream many hope to see accomplished someday. At present, much of that hope and speculation is aimed at our neighboring planet, Mars.
But is it actually possible to terraform Mars using our current technology? According to a new NASA-sponsored study by a pair of scientists who have worked on many NASA missions, the answer is no. Put simply, they argue that there is not enough carbon dioxide gas (CO2) that could practically be put back into Mars’ atmosphere in order to warm Mars, a crucial step in any proposed terraforming process.
The study, titled “Inventory of CO2 available for terraforming Mars“, recently appeared in the journal Nature Astronomy. The study was conducted by Bruce Jakosky – a professor of geological sciences and the associate director of the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado, Boulder – and Christopher S. Edwards, an assistant professor of planetary science at Northern Arizona University and the leader of the Edwards Research Group.
The study was supported in part by NASA through the Mars Atmospheric and Volatile EvolutioN (MAVEN) and Mars Odyssey THEMIS (Thermal Emission Imaging System) projects. Whereas Professor Jakosky was the Principal Investigator on the MAVEN mission, Professor Edwards is a participating scientist on the Mars Science Laboratory Curiosity Rover (MSL), and worked on the Mars Odyssey THEMIS mission (among other Mars missions).
As we explored in a previous article, “How Do We Terraform Mars?“, many methods have been suggested for turning the Red Planet green. Many of these methods call for warming the surface in order to melt the polar ice caps, which would release an abundant amount of CO2 to thicken the atmosphere and trigger a greenhouse effect. This would in turn cause additional CO2 to be released from the soil and minerals, reinforcing the cycle further.
According to many proposals, this would be followed by the introduction of photosynthetic organisms such as cyanobacteria, which would slowly convert the atmospheric CO2 into oxygen gas and elemental carbon. This very method was suggested in a 1976 NASA study, titled “On the Habitability of Mars: An Approach to Planetary Ecosynthesis“. Since that time, multiple studies and even student teams have proposed using cyanobacteria to terraform Mars.
However, after conducting their analysis, Professors Jakosky and Edwards concluded that triggering a greenhouse effect on Mars would not be as simple as all that. For the sake of their study, Jakosky and Edwards relied on about 20 years of data accumulated by multiple spacecraft observations of Mars. As Edwards indicated in a recent NASA press release:
“These data have provided substantial new information on the history of easily vaporized (volatile) materials like CO2 and H2O on the planet, the abundance of volatiles locked up on and below the surface, and the loss of gas from the atmosphere to space.”
Scientists were able to gauge the rate of water loss on Mars by measuring the ratio of water and HDO from today and 4.3 billion years ago. Credit: Kevin Gill
To determine if Mars had enough gases for a greenhouse effect, Jakosky and Edwards analyzed data from NASA’s Mars Reconnaissance Orbiter (MRO) and Mars Odyssey spacecraft to determine the abundance of carbon-bearing minerals in Martian soil and CO2 in polar ice caps. They they used data from NASA’s MAVEN mission to determine the loss of the Martian atmosphere to space. As Prof. Jakosky explained:
“Carbon dioxide (CO2) and water vapor (H2O) are the only greenhouse gases that are likely to be present on Mars in sufficient abundance to provide any significant greenhouse warming… Our results suggest that there is not enough CO2 remaining on Mars to provide significant greenhouse warming were the gas to be put into the atmosphere; in addition, most of the CO2 gas is not accessible and could not be readily mobilized. As a result, terraforming Mars is not possible using present-day technology.”
Although Mars has significant quantities of water ice, previous analyses have shown that water vapor would not be able to sustain a greenhouse effect by itself. In essence, the planet is too cold and the atmosphere too thin for the water to remain in a vaporous or liquid state for very long. According to the team, this means that significant warming would need to take place involving CO2 first.
However, Mars atmospheric pressure averages at about 0.636 kPA, which is the equivalent of about 0.6% of Earth’s air pressure at sea level. Since Mars is also roughly 52% further away from the Sun than Earth (1.523 AUs compared to 1 AU), researchers estimate that a CO2 pressure similar to Earth’s total atmospheric pressure would be needed to raise temperatures enough to allow for water to exist in a liquid state.
Artist’s rendering of a solar storm hitting Mars and stripping ions from the planet’s upper atmosphere. Credits: NASA/GSFC
According to the team’s analysis, melting the polar ice caps (which is the most accessible source of carbon dioxide) would only contribute enough CO2 to double the Martian atmospheric pressure to 1.2% that of Earth’s. Another source is the dust particles in Martian soil, which the researchers estimate would provide up to 4% of the needed pressure. Other possible sources of carbon dioxide are those that are locked in mineral deposits and water-ice molecule structures known as “clathrates”.
However, using the recent NASA spacecraft observations of mineral deposits, Jakosky and Edwards estimate that these would likely yield less than 5% of the require pressure each. What’s more, accessing even the closest minerals to the surface would require significant strip mining, and accessing all the CO2 attached to dust particles would require strip mining the entire planet to a depth of around 90 meters (100 yards).
Accessing carbon-bearing minerals deep in the Martian crust could be a possible solution, but the depth of these deposits is currently unknown. In addition, recovering them with current technology would be incredibly expensive and energy-intensive, making extraction highly impractical. Other methods have been suggested, however, which include importing flourine-based compounds and volatiles like ammonia.
The former was proposed in 1984 by James Lovelock and Michael Allaby in their book, The Greening of Mars. In it, Lovelock and Allaby described how Mars could be warmed by importing chlorofluorocarbons (CFCs) to trigger global warming. While very effective at triggering a greenhouse effect, these compounds are short-lived and would need to be introduced in significant amounts (hence why the team did not consider them).
NASA’s MAVEN spacecraft is depicted in orbit around an artistic rendition of planet Mars, which is shown in transition from its ancient, water-covered past, to the cold, dry, dusty world that it has become today. Credit: NASA
The idea of importing volatiles like ammonia is an even more time-honored concept, and was proposed by Dandridge M. Cole and Donald Cox in their 1964 book, “Islands in Space: The Challenge of the Planetoids, the Pioneering Work“. Here, Cole and Cox indicated how ammonia ices could be transported from the outer Solar System (in the form of iceteroids and comets) and then impacted on the surface.
However, Jakosky and Edwards’ calculations reveal that many thousands of these icy objects would be required, and the sheer distance involved in transporting them make this an impractical solution using today’s technology. Last, but not least, the team considered how atmospheric loss could be prevented (which could be done using a magnetic shield). This would allow for the atmosphere to build up naturally due to outgassing and geologic activity.
Unfortunately, the team estimates that at the current rate at which outgassing occurs, it would take about 10 million years just to double Mars’ current atmosphere. In the end, it appears that any effort to terraform Mars will have to wait for the development of future technologies and more practical methods.
These technologies would most likely involve more cost-effective means for conducting deep-space missions, like nuclear-thermal or nuclear-electric propulsion. The establishment of permanent outposts on Mars would also be an important first step, which could be dedicated to thickening the atmosphere by producing greenhouse gases – something humans have already proven to be very good at here on Earth!
Project Nomad, a concept for terraforming Mars using mobile, factory-skyscrapers from the 2013 Skyscraper Competition. Credit: evolo.com/Antonio Ares Sainz, Joaquin Rodriguez Nuñez, Konstantino Tousidonis Rial
There’s also the possibility of importing methane gas from the outer Solar System, another super-greenhouse gas, which is also indigenous to Mars. While it constitutes only a tiny percentage of the atmosphere, significant plumes have been detected in the past during the summer months. This includes the “tenfold spike” detected by the Curiosity rover in 2014, which pointed to a subterranean source. If these sources could be mined, methane gas might not even need to be imported.
For some time, scientists have known that Mars was not always the cold, dry, and inhospitable place that it is today. As evidenced by the presence of dry riverbeds and mineral deposits that only form in the presence of liquid water, scientists have concluded that billions of years ago, Mars was a warmer, wetter place. However, between 4.2 and 3.7 billion years ago, Mars’ atmosphere was slowly stripped away by solar wind.
This discovery has led to renewed interest in the colonizing and terraforming of Mars. And while transforming the Red Planet to make it suitable for human needs may not be doable in the near-future, it may be possible to get the process started in just a few decades’ time. It may not happen in our lifetime, but that does not mean that the dream of one-day making “Earth’s Twin” truly live up to its name won’t come true.
Carbon dioxide in Earth's atmosphere if half of global-warming emissions are not absorbed. Credit: NASA/JPL/GSFC
By definition, pollution refers to any matter that is “out of place”. In other words, it is what happens when toxins, contaminants, and other harmful products are introduced into an environment, disrupting its normal patterns and functions. When it comes to our atmosphere, pollution refers to the introduction of chemicals, particulates, and biological matter that can be harmful to humans, plants and animals, and cause damage to the natural environment.
Whereas some causes of pollution are entirely natural – being the result of sudden changes in temperature, seasonal changes, or regular cycles – others are the result of human impact (i.e. anthropogenic, or man-made). More and more, the effects of air pollution on our planet, especially those that result from human activity, are of great concern to developers, planners and environmental organizations, given the long-term effect they can have.
Artist's impression of the surface of Venus. Credit: ESA/AOES
Continuing with our “Definitive Guide to Terraforming“, Universe Today is happy to present to our guide to terraforming Venus. It might be possible to do this someday, when our technology advances far enough. But the challenges are numerous and quite specific.
The planet Venus is often referred to as Earth’s “Sister Planet”, and rightly so. In addition to being almost the same size, Venus and Earth are similar in mass and have very similar compositions (both being terrestrial planets). As a neighboring planet to Earth, Venus also orbits the Sun within its “Goldilocks Zone” (aka. habitable zone). But of course, there are many key difference between the planets that make Venus uninhabitable.
For starters, it’s atmosphere over 90 times thicker than Earth’s, its average surface temperature is hot enough to melt lead, and the air is a toxic fume consisting of carbon dioxide and sulfuric acid. As such, if humans want to live there, some serious ecological engineering – aka. terraforming – is needed first. And given its similarities to Earth, many scientists think Venus would be a prime candidate for terraforming, even more so than Mars!
Over the past century, the concept of terraforming Venus has appeared multiple times, both in terms of science fiction and as the subject of scholarly study. Whereas treatments of the subject were largely fantastical in the early 20th century, a transition occurred with the beginning of the Space Age. As our knowledge of Venus improved, so too did the proposals for altering the landscape to be more suitable for human habitation.
Venus is also considered a prime candidate for terraforming. Credit: NASA/JPL/io9.com
Examples in Fiction:
Since the early 20th century, the idea of ecologically transforming Venus has been explored in fiction. The earliest known example is Olaf Stapleton’sLast And First Men(1930), two chapters of which are dedicated to describing how humanity’s descendants terraform Venus after Earth becomes uninhabitable; and in the process, commit genocide against the native aquatic life.
By the 1950s and 60s, owing to the beginning of the Space Age, terraforming began to appear in many works of science fiction. Poul Anderson also wrote extensively about terraforming in the 1950s. In his 1954 novel, The Big Rain, Venus is altered through planetary engineering techniques over a very long period of time. The book was so influential that the term term “Big Rain” has since come to be synonymous with the terraforming of Venus.
In 1991, author G. David Nordley suggested in his short story (“The Snows of Venus”) that Venus might be spun-up to a day-length of 30 Earth days by exporting its atmosphere of Venus via mass drivers. Author Kim Stanley Robinson became famous for his realistic depiction of terraforming in the Mars Trilogy – which included Red Mars, Green Mars and Blue Mars.
In 2012, he followed this series up with the release of 2312, a science fiction novel that dealt with the colonization of the entire Solar System – which includes Venus. The novel also explored the many ways in which Venus could be terraformed, ranging from global cooling to carbon sequestration, all of which were based on scholarly studies and proposals.
Artist’s conception of a terraformed Venus, showing a surface largely covered in oceans. Credit: Wikipedia Commons/Ittiz
Proposed Methods:
The first proposed method of terraforming Venus was made in 1961 by Carl Sagan. In a paper titled “The Planet Venus“, he argued for the use of genetically engineered bacteria to transform the carbon in the atmosphere into organic molecules. However, this was rendered impractical due to the subsequent discovery of sulfuric acid in Venus’ clouds and the effects of solar wind.
In his 1991 study “Terraforming Venus Quickly“, British scientist Paul Birch proposed bombarding Venus’ atmosphere with hydrogen. The resulting reaction would produce graphite and water, the latter of which would fall to the surface and cover roughly 80% of the surface in oceans. Given the amount of hydrogen needed, it would have to harvested directly from one of the gas giant’s or their moon’s ice.
The proposal would also require iron aerosol to be added to the atmosphere, which could be derived from a number of sources (i.e. the Moon, asteroids, Mercury). The remaining atmosphere, estimated to be around 3 bars (three times that of Earth), would mainly be composed of nitrogen, some of which will dissolve into the new oceans, reducing atmospheric pressure further.
Another idea is to bombard Venus with refined magnesium and calcium, which would sequester carbon in the form of calcium and magnesium carbonates. In their 1996 paper, “The stability of climate on Venus“, Mark Bullock and David H. Grinspoon of the University of Colorado at Boulder indicated that Venus’ own deposits of calcium and magnesium oxides could be used for this process. Through mining, these minerals could be exposed to the surface, thus acting as carbon sinks.
A mass of swirling gas and cloud at Venus’ south pole. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford.
However, Bullock and Grinspoon also claim this would have a limited cooling effect – to about 400 K (126.85 °C; 260.33 °F) and would only reduce the atmospheric pressure to an estimated 43 bars. Hence, additional supplies of calcium and magnesium would be needed to achieve the 8×1020 kg of calcium or 5×1020 kg of magnesium required, which would most likely have to be mined from asteroids.
The concept of solar shades has also been explored, which would involve using either a series of small spacecraft or a single large lens to divert sunlight from a planet’s surface, thus reducing global temperatures. For Venus, which absorbs twice as much sunlight as Earth, solar radiation is believed to have played a major role in the runaway greenhouse effect that has made it what it is today.
Such a shade could be space-based, located in the Sun–Venus L1 Lagrangian point, where it would prevent some sunlight from reaching Venus. In addition, this shade would also serve to block the solar wind, thus reducing the amount of radiation Venus’ surface is exposed to (another key issue when it comes to habitability). This cooling would result in the liquefaction or freezing of atmospheric CO², which would then be depsotied on the surface as dry ice (which could be shipped off-world or sequestered underground).
Alternately, solar reflectors could be placed in the atmosphere or on the surface. This could consist of large reflective balloons, sheets of carbon nanotubes or graphene, or low-albedo material. The former possibility offers two advantages: for one, atmospheric reflectors could be built in-situ, using locally-sourced carbon. Second, Venus’ atmosphere is dense enough that such structures could easily float atop the clouds.
Artist’s concept of a Venus cloud city – part of NASA’s High Altitude Venus Operational Concept (HAVOC) plan. Credit: Advanced Concepts Lab/NASA Langley Research Center
NASA scientist Geoffrey A. Landis has also proposed that cities could be built above Venus’ clouds, which in turn could act as both a solar shield and as processing stations. These would provide initial living spaces for colonists, and would act as terraformers, gradually converting Venus’ atmosphere into something livable so the colonists could migrate to the surface.
Another suggestion has to do with Venus’ rotational speed. Venus rotates once every 243 days, which is by far the slowest rotation period of any of the major planets. As such, Venus’s experiences extremely long days and nights, which could prove difficult for most known Earth species of plants and animals to adapt to. The slow rotation also probably accounts for the lack of a significant magnetic field.
To address this, British Interplanetary Society member Paul Birch suggested creating a system of orbital solar mirrors near the L1 Lagrange point between Venus and the Sun. Combined with a soletta mirror in polar orbit, these would provide a 24-hour light cycle.
It has also been suggested that Venus’ rotational velocity could be spun-up by either striking the surface with impactors or conducting close fly-bys using bodies larger than 96.5 km (60 miles) in diameter. There is also the suggestion of using using mass drivers and dynamic compression members to generate the rotational force needed to speed Venus up to the point where it experienced a day-night cycle identical to Earth’s (see above).
Artist’s impression of Venus’ thick atmosphere, complete with lighting strikes and sulfuric acid rains. Credit: ESA
Then there’s the possibility of removing some of Venus’ atmosphere, which could accomplished in a number of ways. For starters, impactors directed at the surface would blow some of the atmosphere off into space. Other methods include space elevators and mass accelerators (ideally placed on balloons or platforms above the clouds), which could gradually scoop gas from the atmosphere and eject it into space.
Potential Benefits:
One of the main reasons for colonizing Venus, and altering its climate for human settlement, is the prospect of creating a “backup location” for humanity. And given the range of choices – Mars, the Moon, and the Outer Solar System – Venus has several things going for it the others do not. All of these highlight why Venus is known as Earth’s “Sister Planet”.
For starters, Venus is a terrestrial planet that is similar in size, mass and composition to Earth. This is why Venus has similar gravity to Earth, which is about of what we experience 90% (or 0.904 g, to be exact. As a result, humans living on Venus would be at a far lower risk of developing health problems associated with time spent in weightlessness and microgravity environments – such as osteoporosis and muscle degeneration.
Venus’s relative proximity to Earth would also make transportation and communications easier than with most other locations in the solar system. With current propulsion systems, launch windows to Venus occur every 584 days, compared to the 780 days for Mars. Flight time is also somewhat shorter since Venus is the closest planet to Earth. At it’s closest approach, it is 40 million km distant, compared to 55 million km for Mars.
On Feb. 5, 1974, NASA’s Mariner 10 mission took this first close-up photo of Venus during 1st gravity assist flyby. Credit: NASA
Another reason has to do with Venus’ runaway greenhouse effect, which is the reason for the planet’s extreme heat and atmospheric density. In testing out various ecological engineering techniques, our scientists would learn a great deal about their effectiveness. This information, in turn, will come in mighty handy in the ongoing fight against Climate Change here on Earth.
And in the coming decades, this fight is likely to become rather intense. As the NOAA reported in March of 2015, carbon dioxide levels in the atmosphere have now surpassed 400 ppm, a level not seen since the the Pliocene Era – when global temperatures and sea level were significantly higher. And as a series of scenarios computed by NASA show, this trend is likely to continue until 2100, with severe consequences.
In one scenario, carbon dioxide emissions will level off at about 550 ppm toward the end of the century, resulting in an average temperature increase of 2.5 °C (4.5 °F). In the second scenario, carbon dioxide emissions rise to about 800 ppm, resulting in an average increase of about 4.5 °C (8 °F). Whereas the increases predicted in the first scenario are sustainable, in the latter scenario, life will become untenable on many parts of the planet.
So in addition to creating a second home for humanity, terraforming Venus could also help to ensure that Earth remains a viable home for our species. And of course, the fact that Venus is a terrestrial planet means that it has abundant natural resources that could be harvested, helping humanity to achieve a “post-scarcity” economy.
Artist’s concept of the High Altitude Venus Operational Concept (HAVOC) mission approaching the planet. Credit: NASA Langley Research Center/YouTube.
Challenges:
Beyond the similarities Venus’ has with Earth (i.e. size, mass and composition), there are numerous differences that would make terraforming and colonizing it a major challenge. For one, reducing the heat and pressure of Venus’ atmosphere would require a tremendous amount of energy and resources. It would also require infrastructure that does not yet exist and would be very expensive to build.
For instance, it would require immense amounts of metal and advanced materials to build an orbital shade large enough to cool Venus’ atmosphere to the point that its greenhouse effect would be arrested. Such a structure, if positioned at L1, would also need to be four times the diameter of Venus itself. It would have to be assembled in space, which would require a massive fleet of robot assemblers.
In contrast, increasing the speed of Venus’s rotation would require tremendous energy, not to mention a significant number of impactors that would have to cone from the outer solar System – mainly from the Kuiper Belt. In all of these cases, a large fleet of spaceships would be needed to haul the necessary material, and they would need to be equipped with advanced drive systems that could make the trip in a reasonable amount of time.
Currently, no such drive systems exist, and conventional methods – ranging from ion engines to chemical propellants – are neither fast or economical enough. To illustrate, NASA’s New Horizons mission took more than 11 years to get make its historic rendezvous with Pluto in the Kuiper Belt, using conventional rockets and the gravity-assist method.
Artist’s impression of the surface of Venus. Credit: ESA/AOES
Meanwhile, the Dawn mission, which relied relied on ionic propulsion, took almost four years to reach Vesta in the Asteroid Belt. Neither method is practical for making repeated trips to the Kuiper Belt and hauling back icy comets and asteroids, and humanity has nowhere near the number of ships we would need to do this.
The same problem of resources holds true for the concept of placing solar reflectors above the clouds. The amount of material would have to be large and would have to remain in place long after the atmosphere had been modified, since Venus’s surface is currently completely enshrouded by clouds. Also, Venus already has highly reflective clouds, so any approach would have to significantly surpass its current albedo (0.65) to make a difference.
And when it comes to removing Venus’ atmosphere, things are equally challenging. In 1994, James B. Pollack and Carl Sagan conducted calculations that indicated that an impactor measuring 700 km in diameter striking Venus at high velocity would less than a thousandth of the total atmosphere. What’s more, there would be diminishing returns as the atmosphere’s density decreases, which means thousands of giant impactors would be needed.
In addition, most of the ejected atmosphere would go into solar orbit near Venus, and – without further intervention – could be captured by Venus’s gravitational field and become part of the atmosphere once again. Removing atmospheric gas using space elevators would be difficult because the planet’s geostationary orbit lies an impractical distance above the surface, where removing using mass accelerators would be time-consuming and very expensive.
Size comparison of Venus and Earth. Credit: NASA/JPL/Magellan
Conclusion:
In sum, the potential benefits of terraforming Venus are clear. Humanity would have a second home, we would be able to add its resources to our own, and we would learn valuable techniques that could help prevent cataclysmic change here on Earth. However, getting to the point where those benefits could be realized is the hard part.
Like most proposed terraforming ventures, many obstacles need to be addressed beforehand. Foremost among these are transportation and logistics, mobilizing a massive fleet of robot workers and hauling craft to harness the necessary resources. After that, a multi-generational commitment would need to be made, providing financial resources to see the job through to completion. Not an easy task under the most ideal of conditions.
Suffice it to say, this is something that humanity cannot do in the short-run. However, looking to the future, the idea of Venus becoming our “Sister Planet” in every way imaginable – with oceans, arable land, wildlife and cities – certainly seems like a beautiful and feasible goal. The only question is, how long will we have to wait?
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Venus really sucks. It’s as hot as an oven with a dense, poisonous atmosphere. But how did it get that way?
Venus sucks. Seriously, it’s the worst. The global temperature is as hot as an oven, the atmospheric pressure is 90 times Earth, and it rains sulfuric acid. Every part of the surface of Venus would kill you dead in moments.
Let’s push Venus into the Sun and be done with that terrible place. Its proximity is lowering our real estate values and who knows what sort of interstellar monstrosities are going to set up shop there, and be constantly knocking on our door to borrow the mower, or a cup or sugar, or sneak into our yard at night and eat all our dolphins.
You might argue that Venus is worth saving because it’s located within the Solar System’s habitable zone, that special place where water could exist in a liquid state on the surface. But we’re pretty sure it doesn’t have any liquid water. Venus may have been better in the past, clearly it started hanging out with wrong crowd, taking a bad turn down a dark road leading it to its current state of disrepair.
Could Venus have been better in the past? And how did it go so wrong? In many ways, Venus is a twin of the Earth. It’s almost the same size and mass as the Earth, and it’s made up of roughly the same elements. And if you stood on the surface of Venus, in the brief moments before you evacuated your bowels and died horribly, you’d notice the gravity feels pretty similar.
In the ancient past, the Sun was dimmer and cooler than it is now. Cool enough that Venus was much more similar to Earth with rivers, lakes and oceans. NASA’s Pioneer spacecraft probed beneath the planet’s thick clouds and revealed that there was once liquid water on the surface of Venus. And with liquid water, there could have been life on the surface and in those oceans.
Here’s where Venus went wrong. It’s about a third closer to the Sun than Earth, and gets roughly double the solar radiation. The Sun has been slowly heating up over the millions and billions of years. At some point, the planet reached a tipping point, where the water on the surface of Venus completely evaporated into the atmosphere.
False color radar topographical map of Venus provided by Magellan. Credit: Magellan Team/JPL/NASA
Water vapor is a powerful greenhouse gas, and this only increased the global temperature, creating a runaway greenhouse effect on Venus. The ultraviolet light from the Sun split apart the water vapor into oxygen and hydrogen. The hydrogen was light enough to escape the atmosphere of Venus into space, while the oxygen recombined with carbon to form the thick carbon dioxide atmosphere we see today. Without that hydrogen, Venus’ water is never coming back.
Are you worried about our changing climate doing that here? Don’t panic. The amount of carbon dioxide released into the atmosphere of Venus is incomprehensible. According to the IPCC, the folks studying global warming, human activities have no chance of unleashing runaway global warming. We’ll just have the regular old, really awful global warming. So, it’s okay to panic a bit, but do it in the productive way that results in your driving your car less.
The Sun is still slowly heating up. And in a billion years or so, temperatures here will get hot enough to boil the oceans away. And then, Earth and Venus will be twins again and then we can push them both into the Sun.
I know, I said the words “climate change”. Feel free to have an argument in the comments below, but play nice and bring science.
Credit: NASA/MRO/Rendering: James Dickson, Brown University
Though the surface of Mars is a dry, dessicated and bitterly cold place today, it is strongly believed that the planet once had rivers, streams, lakes, and flowing water on its surface. Thanks to a combination of spacecraft imagery, remote sensing techniques and surface investigations from landers and rovers, ample evidence has been assembled to support this theory.
However, it is hard to reconcile this view with the latest climate models of Mars which suggest that it should have been a perennially cold and icy place. But according to a new study, the presence of warm, flowing water may have been an episodic occurrence, something that happened for decades or centuries when the planet was warmed sufficiently by volcanic eruptions and greenhouse gases.
The study, which was conducted by scientists from Brown University and Israel’s Weizmann Institute of Science, suggests that warmth and water flow on ancient Mars were probably episodic, related to brief periods of volcanic activity that spewed tons of greenhouse-inducing sulfur dioxide gas into the atmosphere.
The work combines the effect of volcanism with the latest climate models of early Mars and suggests that periods of temperatures warm enough for water to flow likely lasted for only tens or hundreds of years at a time.
The notion that Mars had surface water predates the space age by centuries. Long before Percival Lowell observed what he thought were “canals” on the Martian surface in 1877, the polar ice caps and dark spots on the surface were being observed by astronomers who thought that they were indications of liquid water.
Curiosity found evidence of an ancient, flowing stream on Mars at a few sites, including the “Hottah” rock outcrop pictured here. Credit: NASA/JPL
But with all that’s been learned about Mars in recent years, the mystery of the planet’s ancient water has only deepened. The latest generation of climate models for early Mars suggests that the atmosphere was too thin to heat the planet enough for water to flow. Billions of years ago, the sun was also much dimmer than it is today, which further complicates this picture of a warmer early Mars.
“These new climate models that predict a cold and ice-covered world have been difficult to reconcile with the abundant evidence that water flowed across the surface to form streams and lakes,” said James W. Head, professor of earth, environmental and planetary sciences at Brown University and co-author of the new paper with Weizmann’s Itay Halevy. “This new analysis provides a mechanism for episodic periods of heating and melting of snow and ice that could have each lasted decades to centuries.”
Halevy and Head explored the idea that heating may have been linked to periodic volcanism. Many of the geological features that suggest water was flowing on the Martian surface have been dated to 3.7 billion years ago, a time when massive volcanoes are thought to have been active.
And whereas on Earth, widespread volcanism has often led to global dimming rather than warming – on account of sulfuric acid particles reflecting the sun’s rays – Head and Halevy think the effects may have been different in Mars’ dusty atmosphere.
To test this theory, they created a model of how sulfuric acid might react with the widespread dust in the Martian atmosphere. The work suggests that those sulfuric acid particles would have glommed onto dust particles and reduced their ability to reflect the sun’s rays. Meanwhile, sulfur dioxide gas would have produced enough greenhouse effect to warm the Martian equatorial region so that water could flow.
Image of the McMurdo Dry Valleys, Antarctica, acquired by Landsat 7’s Enhanced Thematic Mapper plus (ETM+) instrument. Credit: NASA/EO
Head has been doing fieldwork for years in Antarctica and thinks the climate on early Mars may have been very similar to what he has observed in the cold, desert-like.
“The average yearly temperature in the Antarctic Dry Valleys is way below freezing, but peak summer daytime temperatures can exceed the melting point of water, forming transient streams, which then refreeze,” Head said. “In a similar manner, we find that volcanism can bring the temperature on early Mars above the melting point for decades to centuries, causing episodic periods of stream and lake formation.”
As that early active volcanism on Mars ceased, so did the possibility of warmer temperatures and flowing water.
According to Head, this theory might also help in the ongoing search for signs that Mars once hosted life. If it ever did exist, this new research may offer clues as to where the fossilized remnants ended up.
“Life in Antarctica, in the form of algal mats, is very resistant to extremely cold and dry conditions and simply waits for the episodic infusion of water to ‘bloom’ and develop,” he said. “Thus, the ancient and currently dry and barren river and lake floors on Mars may harbor the remnants of similar primitive life, if it ever occurred on Mars.”
