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.
Discovering new things in space is a regular occurrence. Astronomers keep finding more distant objects in the outer reaches of the Solar System. Worlds like ‘The Goblin,’ ‘FarOut,’ and ‘FarFarOut‘ are stretching the limits of what our Solar System actually is.
But finding new things in the inner Solar System is rare.
A team of researchers in Japan has discovered a gigantic streak structure in the cloud tops of Venus. The discovery is based on observations of Venus by the Japanese spacecraft Akatsuki. The findings were published in January 9th in the journal Nature Communications.
Venus is unlike any other planet in the Solar System. The entire planet is shrouded in thick clouds of sulfuric acid between altitudes of 45 km to 70 km. This thick shroud has prevented scientists from studying Earth’s so-called “sister planet” in detail. But Japanese researchers are making progress.
Hello all. I hope our readers don’t mind that I’m taking a bit of a diversion here today to engage in a little shameless self-promotion. Basically, I wanted to talk about my recently-published novel – The Jovian Manifesto. This book is the sequel to The Cronian Incident, which was published last year (and was a little shamelessly promoted at the time).
However, I also wanted to take this opportunity to talk about hard science fiction and how writing for a science publication helped me grow as a writer. By definition, hard sci-fi refers to stories where scientific accuracy is emphasized. This essentially means that the technology in the story conforms to established science and/or what is believed to be feasible in the future.
Welcome to the 583rd Carnival of Space! The Carnival is a community of space science and astronomy writers and bloggers, who submit their best work each week for your benefit. We have a fantastic roundup today so now, on to this week’s worth of stories! Continue reading “Carnival of Space #583”
In the coming decades, NASA and other space agencies hope to mount some ambitious missions to other planets in our Solar System. In addition to studying Mars and the outer Solar System in greater detail, NASA intends to send a mission to Venus to learn more about the planet’s past. This will include studying Venus’ upper atmosphere to determine if the planet once had liquid water (and maybe even life) on its surface.
In order to tackle this daunting challenge, NASA recently partnered with Black Swift Technologies – a Boulder-based company specializing in unmanned aerial systems (UAS) – to build a drone that could survive in Venus’ upper atmosphere. This will be no easy task, but if their designs should prove equal to the task, NASA will be awarding the company a lucrative contract for a Venus aerial drone.
In recent years, NASA has taken a renewed interest in Venus, thanks to climate models that have indicated that it (much like Mars) may have also had liquid water on its surface at one time. This would have likely consisted of a shallow ocean that covered much of the planet’s surface roughly 2 billion years ago, before the planet suffered a runaway Greenhouse Effect that left it the hot and hellish world it is today.
In addition, a recent study – which included scientists from NASA’s Ames Research Center and Jet Propulsion Laboratory – indicated that there could be microbial life in Venus’ cloud tops. As such, there is considerable motivation to send aerial platforms to Venus that would be capable of studying Venus’ cloud tops and determining if there are any traces of organic life or indications of the planet’s past surface water there.
As Jack Elston, the co-founded of Black Swift Technologies, explained in an interview with the Daily Camera:
“They’re looking for vehicles to explore just above the cloud layer. The pressure and temperatures are similar to what you’d find on Earth, so it could be a good environment for looking for evidence of life. The winds in the upper atmosphere of Venus are incredibly strong, which creates design challenge.”
To meet this challenge, the company intends to create a drone that will use these strong winds to keep the craft aloft while reducing the amount of electricity it needs. So far, NASA has awarded an initial six-month contract to the company to design a drone and provided specifications on what it needs. This contract included a $125,000 grant by the federal governments’ Small Business Innovation Research program.
This program aims to encourage “domestic small businesses to engage in Federal Research/Research and Development (R/R&D) that has the potential for commercialization.” The company hopes to use some of this grant money to take on more staff and build a drone that NASA would be confident about sending int Venus’ upper atmosphere, where conditions are particularly challenging.
As Elston explained to Universe Today via email, these challenges represent an opportunity for innovation:
“Our project centers around a unique aircraft and method for harvesting energy from Venus’s upper atmosphere that doesn’t require additional sources of energy for propulsion. Our experience working on unmanned aircraft systems that interact with severe convective storms on Earth will hopefully provide a valuable contribution to the ongoing discussion for how best to explore this turbulent environment. Additionally, the work we do will help inform better designs of our own aircraft and should lead to longer observation times and more robust aircraft to observe everything from volcanic plumes to hurricanes.”
At the end of the six month period, Black Swift will present its concept to NASA for approval. “If they like what we’ve come up with, they’ll fund another two-year project to build prototypes,” said Elston. “That second-phase contract is expected to be worth $750,000.”
This is not the first time that Black Swift has partnered with NASA to created unmanned aerial vehicles to study harsh environments. Last year, the company was awarded a second phase contract worth $875,000 to build a drone that could monitor the temperature, gas levels, winds and pressure levels inside the volcanoes of Costa Rica. After a series of test flights, the drone is expected to be deployed to Hawaii, where it will study the geothermal activity occurring there.
All of these missions aim to reach Venus and brave its harsh conditions in order to determine whether or not “Earth’s Sister Planet” was once a more habitable planet, and how it evolved over time to become the hot and hellish place it is today.
It is a well-known fact among Earth scientists that our planet periodically undergoes major changes in its climate. Over the course of the past 200 million years, our planet has experienced four major geological periods (the Triassic, Jurassic and Cretaceous and Cenozoic) and one major ice age (the Pliocene-Quaternary glaciation), all of which had a drastic impact on plant and animal life, as well as effecting the course of species evolution.
For decades, geologists have also understood that these changes are due in part to gradual shifts in the Earth’s orbit, which are caused by Venus and Jupiter, and repeat regularly every 405,000 years. But it was not until recently that a team of geologists and Earth scientists unearthed the first evidence of these changes – sediments and rock core samples that provide a geological record of how and when these changes took place.
As noted, the idea that Earth experiences periodic changes in its climate (which are related to changes in its orbit) has been understood for almost a century. These changes consist of Milankovitch Cycles, which consist of a 100,000-year cycle in the eccentricity of Earth’s orbit, a 41,000-year cycle in the tilt of Earth’s axis relative to its orbital plane, and a 21,000-year cycle caused by changes in the planet’s axis.
Combined with the 405,000-year swing, which is the result of Venus and Jupiter’s gravitational influence, these shifts cause changes in how much solar energy reaches parts of our planet, which in turn influences Earth’s climate. Based on fossil records, these cycles are also known to have had a profound impact on life on Earth, which likely had an effect on the course of species of evolution. As Prof. Bent explained in a Rutgers Today press release:
“The climate cycles are directly related to how Earth orbits the sun and slight variations in sunlight reaching Earth lead to climate and ecological changes. The Earth’s orbit changes from close to perfectly circular to about 5 percent elongated especially every 405,000 years.”
For the sake of their study, Prof. Kent and his colleagues obtained sediment samples from the Newark basin, a prehistoric lake that spanned most of New Jersey, and a core rock sample from the Chinle Formation in Petrified Forest National Park in Arizona. This core rock measured about 518 meters (1700 feet) long, 6.35 cm (2.5 inches) in diameter, and was dated to the Triassic Period – ca. 202 to 253 million years ago.
The team then linked reversals in Earth’s magnetic field – where the north and south pole shift – to sediments with and without zircons (minerals with uranium that allow for radioactive dating) as well as to climate cycles in the geological record. What these showed was that the 405,000-years cycle is the most regular astronomical pattern linked to Earth’s annual orbit around the Sun.
The results further indicated that the cycle been stable for hundreds of millions of years and is still active today. As Prof. Kent explained, this constitutes the first verifiable evidence that celestial mechanics have played a historic role in natural shifts in Earth’s climate. As Prof. Kent indicated:
“It’s an astonishing result because this long cycle, which had been predicted from planetary motions through about 50 million years ago, has been confirmed through at least 215 million years ago. Scientists can now link changes in the climate, environment, dinosaurs, mammals and fossils around the world to this 405,000-year cycle in a very precise way.”
Previously, astronomers were able to calculate this cycle reliably back to around 50 million years, but found that the problem became too complex prior to this because too many shifting motions came into play. “There are other, shorter, orbital cycles, but when you look into the past, it’s very difficult to know which one you’re dealing with at any one time, because they change over time,” said Prof. Kent. “The beauty of this one is that it stands alone. It doesn’t change. All the other ones move over it.”
In addition, scientists were unable to obtain accurate dates as to when Earth’s magnetic field reversed for 30 million years of the Late Triassic – between ca. 201.3 and 237 million years ago. This was a crucial period for the evolution of terrestrial life because it was when the Supercontinent of Pangaea broke up, and also when the dinosaurs and mammals first appeared.
This break-up led to the formation of the Atlantic Ocean as the continents drifted apart and coincided with a mass extinction event by the end of the period that effected the dinosaurs. With this new evidence, geologists, paleontologists and Earth scientists will be able to develop very precise timelines and accurately categorize fossil evidence dated to this period, which show differences and similarities over wide-ranging areas.
This research, and the ability to create accurate geological and climatological timelines that go back over 200 million years, is sure to have drastic implications. Not only will climate studies benefit from it, but also our understanding of how life, and even how our Solar System, evolved. What emerges from this could include a better understanding of how life could emerge in other star systems.
After all, if our search for extra-solar life life comes down to what we know about life on Earth, knowing more about how it evolved here will better the odds of finding it out there.
In the search for life beyond Earth, scientists have turned up some very interesting possibilities and clues. On Mars, there are currently eight functioning robotic missions on the surface of or in orbit investigating the possibility of past (and possibly present) microbial life. Multiple missions are also being planned to explore moons like Titan, Europa, and Enceladus for signs of methanogenic or extreme life.
But what about Earth’s closest neighboring planet, Venus? While conditions on its surface are far too hostile for life as we know it there are those who think it could exist in its atmosphere. In a new study, a team of international researchers addressed the possibility that microbial life could be found in Venus’ cloud tops. This study could answer an enduring mystery about Venus’ atmosphere and lead to future missions to Earth’s “Sister Planet”.
For the sake of their study, the team considered the presence of UV contrasts in Venus’ upper atmosphere. These dark patches have been a mystery since they were first observered nearly a century ago by ground-based telescopes. Since then, scientists have learned that they are made up of concentrated sulfuric acid and other unknown light-absorbing particles, which the team argues could be microbial life.
As Limaye indicated in a recent University of Wisconsin-Madison press statement:
“Venus shows some episodic dark, sulfuric rich patches, with contrasts up to 30 – 40 percent in the ultraviolet, and muted in longer wavelengths. These patches persist for days, changing their shape and contrasts continuously and appear to be scale dependent.”
To illustrate the possibility that these streaks are the result of microbial life, the team considered whether or not extreme bacteria could survive in Venus’ cloud tops. For instance, the lower cloud tops of Venus (47.5 to 50.5 km above the surface) are known to have moderate temperature conditions (~60 °C; 140 °F) and pressure conditions that are similar to that of Earth at sea level (101.325 kPa).
This is far more hospitable than conditions on the surface, where temperatures reach 737 K (462 C; 860 F) and atmospheric pressure is 9200 kPa (92 times that of Earth at sea level). In addition, they considered how on Earth, bacteria has been found at altitudes as high as 41 km (25 mi). On top of that, there are many cases where extreme bacteria here on Earth that could survive in an acidic environment.
As Rakesh Mogul, a professor of biological chemistry at California State Polytechnic University and a co-author on the study, indicated, “On Earth, we know that life can thrive in very acidic conditions, can feed on carbon dioxide, and produce sulfuric acid.” This is consistent with the presence of micron-sized sulfuric acid aerosols in Venus upper atmosphere, which could be a metabolic by-product.
In addition, the team also noted that according to some models, Venus had a habitable climate with liquid water on its surface for as long as two billion years – which is much longer than what is believed to have occurred on Mars. In short, they speculate that life could have evolved on the surface of Venus and been swept up into the atmosphere, where it survived as the planet experienced its runaway greenhouse effect.
This study expands on a proposal originally made by Harold Morowitz and famed astronomer Carl Sagan in 1967 and which was investigated by a series of probes sent to Venus between 1962 and 1978. While these missions indicated that surface conditions on Venus ruled out the possibility of life, they also noted that conditions in the lower and middle portions of Venus’ atmosphere – 40 to 60 km (25 – 27 mi) altitude – did not preclude the possibility of microbial life.
For years, Limaye has been revisiting the idea of exploring Venus’ atmosphere for signs of life. The inspiration came in part from a chance meeting at a teachers workshop with Grzegorz Slowik – from the University of Zielona Góra in Poland and a co-author on the study – who told him of how bacteria on Earth have light-absorbing properties similar to the particles that make up the dark patches observed in Venus’ clouds.
While no probe that has sampled Venus’ atmosphere has been capable of distinguishing between organic and inorganic particles, the ones that make up Venus’ dark patches do have comparable dimensions to some bacteria on Earth. According to Limaye and Mogul, these patches could therefore be similar to algae blooms on Earth, consisting of bacteria that metabolizes the carbon dioxide in Venus’ atmosphere and produces sulfuric acid aerosols.
In the coming years, Venus’ atmosphere could be explored for signs of microbial life by a lighter than air aircraft. One possibility is the Venus Aerial Mobil Platform (VAMP), a concept currently being researched by Northrop Grumman (shown above). Much like lighter-than-air concepts being developed to explore Titan, this vehicle would float and fly around in Venus’ atmosphere and search the cloud tops for biosignatures.
Another possibility is NASA’s possible participation in the Russian Venera-D mission, which is currently scheduled to explore Venus during the late 2020s. This mission would consist of a Russian orbiter and lander to explore Venus’ atmosphere and surface while NASA would contribute a surface station and maneuverable aerial platform.
Another mystery that such a mission could explore, which has a direct bearing on whether or not life may still exist on Venus, is when Venus’ liquid water evaporated. In the last billion years or so, the extensive lava flows that cover the surface have either destroyed or covered up evidence of the planet’s early history. By sampling Venus’ clouds, scientists could determine when all of the planet’s liquid water disappeared, triggering the runaway greenhouse effect that turned it into a hellish landscape.
NASA is currently investigating other concepts to explore Venus’ hostile surface and atmosphere, including an analog robot and a lander that would use a Sterling engine to turn Venus’ atmosphere into a source of power. And with enough time and resources, we might even begin contemplating building floating cities in Venus atmosphere, complete with research facilities.
On February 6th, 2018, SpaceX successfully launched its Falcon Heavy rocket into orbit. This was a momentous occasion for the private aerospace company and represented a major breakthrough for spaceflight. Not only is the Falcon Heavy the most powerful rocket currently in service, it is also the first heavy launch vehicle that relies on reusable boosters (two of which were successfully retrieved after the launch).
Equally interesting was the rocket’s cargo, which consisted of Musk’s cherry-red Tesla Roadster with a spacesuit in the driver’s seat. According to Musk, this vehicle and its “pilot” (Starman), will eventually achieve a Hohmann Transfer Orbit with Mars and remain there for up to a billion years. However, according to a new study, there’s a small chance that the Roadster will collide with Venus or Earth instead in a few eons.
As we indicated in a previous post, Musk’s original flight plan has the potential to place the Roadster into a stable orbit around Mars… after a fashion. According to Max Fagin, an aerospace engineer from Colorado and a space camp alumni, the Roadster will get close enough to Mars to establish an orbit by October of 2018. However, this orbit would not rule out close encounters with Earth over the course of the next few million years.
For the sake of their study, Rein and his colleagues considered how such close encounters might alter the Roadster’s orbit in that time. Using data from NASA’s HORIZONS interface to determine the initial positions of all Solar planets and the Roadster, the team calculated the likelihood of future close encounters between the vehicle and the terrestrial planets, and how likely a resulting collision would be.
As they indicated, the Roadster bears some similarities to Near-Earth Asteroids (NEAs) and ejecta from the Earth-Moon system. In short, NEAs permeate the inner Solar System, regularly crossing the orbits of terrestrial planets and experiencing close encounters with them (resulting in the occasional collision). In addition, ejecta from the Earth and Moon also experience close encounters with the terrestrial planets and collide with them.
However, the Tesla Roadster is unique in two key respects: For one, it originated from Earth rather than being pulled from the Asteroid Belt into the inner Solar System by strong resonances. Second, it had a higher ejection velocity when it left Earth, which tends to result in fewer impacts. “Given the peculiar initial conditions and even stranger object, it therefore remains an interesting question to probe its dynamics and eventual fate,” they claim.
Another challenge was how the probability of an impact will change drastically over time. While the chance of a collision can be ruled out in the short run (i.e. the next few years), the Roadster’s chaotic orbit is difficult to predict over the course of subsequent close encounters. As such, the team performed a statistical calculation to see how the orbit and velocity of the Roadster would change over time. As they state in their study:
“Given that the Tesla was launched from Earth, the two objects have intersecting orbits and repeatedly undergo close encounters. The bodies reach the same orbital longitude on their synodic timescale of ~2.8 yrs.”
They began by considering how the Roadster’s orbit would evolve over the course of its next 48 orbits, which would encompass the next 1000 years. They then expanded the analysis to consider long-term evolution, which encompassed 240 orbits over the course of the next 3.5 million years. What they found was that on a million-year timescale, the orbit of the Roadster remains in a region dominated by close encounters with Earth.
However, over time, their simulations show that the Roadster will experience changes in eccentricity due to resonant and secular effects. This will result in interactions more frequent interactions between the Roadster and Venus over time, and close encounters with Mars becoming possible. Over long enough timescales, the team even anticipates that interactions with Mercury’s orbit will be possible (though unlikely).
In the end, their simulations revealed that over the course of a million years and beyond, the probability of a collision with a terrestrial planet is unlikely, but not impossible. And while the odds are slim, they favor an eventual collision with Earth. Or as they put it:
“Although there were several close encounters with Mars in our simulations, none of them resulted in a physical collision. We find that there is a ~6% chance that the Tesla will collide with Earth and a ~2.5% chance that it will collide with Venus within the next 1 Myr. The collision rate goes down slightly with time. After 3 Myr the probability of a collision with Earth is ~11%. We observed only one collision with the Sun within 3 Myr.”
Given the Musk hoped that his Roadster would remain in orbit of Mars for one billion years, and that aliens might eventually find it, the prospect of it colliding with Earth or Venus is a bit of a letdown. Why bother sending such a unique payload into space if it’s just going to come back? Still, the odds that it will be drifting through space for millions of years remains a distinct possibility.
And if there are any worries that the Roadster will pose a threat to future missions or Earth itself, consider the message Starman was looking at during his ascent into space – Don’t Panic! Assuming humanity is even alive eons from now, the far greater danger will be that such an antique will burn up in our atmosphere. After millions of years, Starman is sure to be a big celebrity!
For many reasons, Venus is sometimes referred to as “Earth’s Twin” (or “Sister Planet”, depending on who you ask). Like Earth, it is terrestrial (i.e. rocky) in nature, composed of silicate minerals and metals that are differentiated between an iron-nickel core and silicate mantle and crust. But when it comes to their respective atmospheres and magnetic fields, our two planets could not be more different.
For some time, astronomers have struggled to answer why Earth has a magnetic field (which allows it to retain a thick atmosphere) and Venus do not. According to a new study conducted by an international team of scientists, it may have something to do with a massive impact that occurred in the past. Since Venus appears to have never suffered such an impact, its never developed the dynamo needed to generate a magnetic field.
The study, titled “Formation, stratification, and mixing of the cores of Earth and Venus“, recently appeared in the scientific journal Earth and Science Planetary Letters. The study was led by Seth A. Jacobson of Northwestern University, and included members from the Observatory de la Côte d’Azur, the University of Bayreuth, the Tokyo Institute of Technology, and the Carnegie Institution of Washington.
For the sake of their study, Jacobson and his colleagues began considering how terrestrial planets form in the first place. According to the most widely-accepted models of planet formation, terrestrial planets are not formed in a single stage, but from a series of accretion events characterized by collisions with planetesimals and planetary embryos – most of which have cores of their own.
Recent studies on high-pressure mineral physics and on orbital dynamics have also indicated that planetary cores develop a stratified structure as they accrete. The reason for this has to do with how a higher abundance of light elements are incorporated in with liquid metal during the process, which would then sink to form the core of the planet as temperatures and pressure increased.
Such a stratified core would be incapable of convection, which is believed to be what allows for Earth’s magnetic field. What’s more, such models are incompatible with seismological studies that indicate that Earth’s core consists mostly of iron and nickel, while approximately 10% of its weight is made up of light elements – such as silicon, oxygen, sulfur, and others. It’s outer core is similarly homogeneous, and composed of much the same elements.
As Dr. Jacobson explained to Universe Today via email:
“The terrestrial planets grew from a sequence of accretionary (impact) events, so the core also grew in a multi-stage fashion. Multi-stage core formation creates a layered stably stratified density structure in the core because light elements are increasingly incorporated in later core additions. Light elements like O, Si, and S increasingly partition into core forming liquids during core formation when pressures and temperatures are higher, so later core forming events incorporate more of these elements into the core because the Earth is bigger and pressures and temperatures are therefore higher.
“This establishes a stable stratification which prevents a long-lasting geodynamo and a planetary magnetic field. This is our hypothesis for Venus. In the case of Earth, we think the Moon-forming impact was violent enough to mechanically mix the core of the Earth and allow a long-lasting geodynamo to generate today’s planetary magnetic field.”
To add to this state of confusion, paleomagnetic studies have been conducted that indicate that Earth’s magnetic field has existed for at least 4.2 billion years (roughly 340 million years after it formed). As such, the question naturally arises as to what could account for the current state of convection and how it came about. For the sake of their study, Jacobson and his team considering the possibility that a massive impact could account for this. As Jacobson indicated:
“Energetic impacts mechanically mix the core and so can destroy stable stratification. Stable stratification prevents convection which inhibits a geodynamo. Removing the stratification allows the dynamo to operate.”
Basically, the energy of this impact would have shaken up the core, creating a single homogeneous region within which a long-lasting geodynamo could operate. Given the age of Earth’s magnetic field, this is consistent with the Theia impact theory, where a Mars-sized object is believed to have collided with Earth 4.51 billion years ago and led to the formation of the Earth-Moon system.
This impact could have caused Earth’s core to go from being stratified to homogeneous, and over the course of the next 300 million years, pressure and temperature conditions could have caused it to differentiate between a solid inner core and liquid outer core. Thanks to rotation in the outer core, the result was a dynamo effect that protected our atmosphere as it formed.
The seeds of this theory were presented last year at the 47th Lunar and Planetary Science Conference in The Woodlands, Texas. During a presentation titled “Dynamical Mixing of Planetary Cores by Giant Impacts“, Dr. Miki Nakajima of Caltech – one of the co-authors on this latest study – and David J. Stevenson of the Carnegie Institution of Washington. At the time, they indicated that the stratification of Earth’s core may have been reset by the same impact that formed the Moon.
It was Nakajima and Stevenson’s study that showed how the most violent impacts could stir the core of planets late in their accretion. Building on this, Jacobson and the other co-authors applied models of how Earth and Venus accreted from a disk of solids and gas about a proto-Sun. They also applied calculations of how Earth and Venus grew, based on the chemistry of the mantle and core of each planet through each accretion event.
The significance of this study, in terms of how it relates to the evolution of Earth and the emergence of life, cannot be understated. If Earth’s magnetosphere is the result of a late energetic impact, then such impacts could very well be the difference between our planet being habitable or being either too cold and arid (like Mars) or too hot and hellish (like Venus). As Jacobson concluded:
“Planetary magnetic fields shield planets and life on the planet from harmful cosmic radiation. If a late, violent and giant impact is necessary for a planetary magnetic field then such an impact may be necessary for life.”
Looking beyond our Solar System, this paper also has implications in the study of extra-solar planets. Here too, the difference between a planet being habitable or not may come down to high-energy impacts being a part of the system’s early history. In the future, when studying extra-solar planets and looking for signs of habitability, scientists may very well be forced to ask one simple question: “Was it hit hard enough?”