Venus is often referred to as “Earth’s sister planet“, owing to the number of similarities between them. Like Earth, Venus is a terrestrial (aka. rocky) planet and it resides with our Sun’s Circumstellar Habitable Zone (CHZ). And for some time, scientists have theorized that billions of years ago, Venus had oceans on its surface and was habitable – aka. not the hot and hellish place it is today.
However, after examining radar data on the Ovda Fluctus lava flow, a team scientists at the Lunar and Planetary Institute concluded that the highlands on Venus are likely to be composed of basaltic lava rock instead of granite. This effectively punches a hole in the main argument for Venus having oceans in the past, which is that the Ovda Regio highlands plateau formed in the presence of water.
In 1978, NASA’s Pioneer Venus (aka. Pioneer 12) mission reached Venus (“Earth’s Sister”) and found indications that Venus may have once had oceans on its surface. Since then, several missions have been sent to Venus and gathered data on its surface and atmosphere. From this, a picture has emerged of how Venus made the transition from being an “Earth-like” planet to the hot and hellish place it is today.
It all started about 700 million years ago when a massive resurfacing event triggered a runaway Greenhouse Effect that caused Venus’s atmosphere to become incredibly dense and hot. This means that for 2 to 3 billion years after Venus formed, the planet could have maintained a habitable environment. According to a recent study, that would have been long enough for life to have emerged on “Earth’s Sister”.
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.
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.
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.
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.
Where have all the planets gone? The end of February 2018 sees the three naked eye outer planets – Mars, Jupiter and Saturn — hiding in the dawn. It takes an extra effort to brave the chill of a February morning, for sure. The good news is, the two inner planets – Mercury and Venus – begin favorable dusk apparitions this week, putting on a fine sunset showing in March.
Venus in 2018: Venus begins the month of March as a -3.9 magnitude, 10” disk emerging from behind the Sun. Venus is already over 12 degrees east of the Sun this week, as it begins its long chase to catch up to the Earth. Venus always emerges from behind the Sun in the dusk, lapping the Earth about eight months later as it passes through inferior conjunction between the Sun and the Earth as it ventures into the dusk sky.
Follow that planet, as Venus reaches greatest elongation at 45.9 degrees east of the Sun on August 17th. Venus occupies the apex of a right triangle on this date, with the Earth at the end of one vertice, and the Sun at the end of the other.
Mercury joins the fray in early March, as the fleeting innermost world races up to meet Venus in the dusk. March 4th is a great date to check Mercury off of your life list, as the -1.2 magnitude planet passes just 66′ – just over a degree, or twice the span of a Full Moon – from Venus. Mercury reaches greatest elongation 18.4 degrees east of the Sun on March 15th.
And the Moon makes three on the evening of March 18th, as Mercury, Venus and the slim waxing crescent Moon form a line nine degrees long.
It’s a bit of a cosmic irony: Venus, the closest planet to the Earth, is also eternally shrouded in clouds and appears featureless at the eyepiece. The most notable feature Venus exhibits are its phases, similar to the Moon’s. Things get interesting as Venus reaches half phase near greatest elongation. After that, the disk of Venus swells in size but thins down to a slender crescent. Venus’s orbit is tilted 3.4 degrees relative to the ecliptic, and on some years, you can follow it right through inferior conjunction from the dusk to the dawn sky. Unfortunately, this also means that Venus usually misses transiting the disk of the Sun, as it last did on June 5-6th, 2012, and won’t do again until just under a century from now on December 10-11th, 2117.
Small consolation prize: Mercury, a much more frequent solar transiter, will do so again next year on November 11-12th, 2019.
Amateur astronomers have, however, managed to tease out detail from the Venusian cloudtops using ultraviolet filters. And check out this amazing recent image of Venus courtesy of the Japanese Space Agency’s Akatsuki spacecraft:
It’s one of our favorite astro-challenges. Can you see Venus in the daytime? Once you’ve seen it, it’s surprisingly easily to spy… the main difficulty is to get your eyes to focus in on it without any other references against a blank sky. The crescent Moon makes a great visual aid in this quest; although the Moon’s reflectivity or albedo is actually much lower than Venus’s, it’s larger apparent size in the sky makes it stand out. Key upcoming dates to see Venus near the Moon around greatest elongation are April 17th, May 17th, June 16th, July 15th, and Aug 14th.
Apparitions of Venus also follow a predictable eight year cycle. This occurs because 13 orbits of Venus very nearly equals eight orbits of the Earth. For example, Venus will resume visiting the Pleiades star cluster during the dusk 2020 apparition, just like it did back before 2012.
Phenomena of Venus
When does Venus appear half illuminated to you? This stage is known as dichotomy, and its actual observed point can often be several days off from its theoretical arrival. Also keep an eye out for the Ashen Light of Venus, a faint illumination of the planet’s night side during crescent phase, similar to the familiar sight seen on the crescent Moon. Unlike the Moon, however, Venus has no nearby body to illuminate its nighttime side… What’s going on here? Is this just the psychological effect of the brain filling in what the eye sees when it looks at the dazzling curve of the crescent Venus, or is it something real? Long reported by observers, a 2014 study suggests that a nascent air-glow or aurora may persist on the broiling night side of Venus.
All thoughts to ponder, as you follow Venus emerging into the dusk sky this March.
The weather on Venus is like something out of Dante’s Inferno. The average surface temperature – 737 K (462 °C; 864 °F) – is hot enough to melt lead and the atmospheric pressure is 92 times that of Earth’s at sea level (9.2 MPa). For this reason, very few robotic missions have ever made it to the surface of Venus, and those that have did not last long – ranging from about 20 minutes to just over two hours.
Hence why NASA, with an eye to future missions, is looking to create robotic missions and components that can survive inside Venus’ atmosphere for prolonged periods of time. These include the next-generation electronics that researchers from NASA Glenn Research Center (GRC) recently unveiled. These electronics would allow a lander to explore Venus surface for weeks, months, or even years.
In the past, landers developed by the Soviets and NASA to explore Venus – as part of the Venera and Mariner programs, respectively – relied on standard electronics, which were based on silicon semiconductors. These are simply not capable of operating in the temperature and pressure conditions that exist on the surface of Venus, and therefore required that they have protective casings and cooling systems.
Naturally, it was only a matter of time before these protections failed and the probes stopped transmitting. The record was achieved by the Soviets with their Venera 13 probe, which transmitted for 127 minutes between its descent and landing. Looking ahead, NASA and other space agencies want to develop probes that can gather as much information as they can on Venus’s atmosphere, surface, and geological history before they time out.
To do this, a team from NASA’s GRC has been working to develop electronics that rely on silcon carbide (SiC) semiconductors, which would be capable of operating at or above Venus’ temperatures. Recently, the team conducted a demonstration using the world’s first moderately-complex SiC-based microcircuits, which consisted of tens or more transistors in the form of core digital logic circuits and analog operation amplifiers.
These circuits, which would be used throughout the electronic systems of a future mission, were able to operate for up to 4000 hours at temperatures of 500 °C (932 °F) – effectively demonstrated that they could survive in Venus-like conditions for prolonged periods. These tests took place in the Glenn Extreme Environments Rig (GEER), which simulated Venus’ surface conditions, including both the extreme temperature and high pressure.
Back in April of 2016, the GRC team tested a SiC 12-transistor ring oscillator using the GEER for a period of 521 hours (21.7 days). During the test, they raised they subjected the circuits to temperatures of up to 460 °C (860 °F), atmospheric pressures of 9.3 MPa and supercritical levels of CO² (and other trace gases). Throughout the entire process, the SiC oscillator showed good stability and kept functioning.
This test was ended after 21 days due to scheduling reasons, and could have gone on much longer. Nevertheless, the duration constituted a significant world record, being orders of magnitude longer than any other demonstration or mission that has been conducted. Similar tests have shown that ring oscillator circuits can survive for thousands of hours at temperatures of 500 °C (932 °F) in Earth-air ambient conditions.
Such electronics constitute a major shift for NASA and space exploration, and would enable missions that were previously impossible. NASA’s Science Mission Direction (SMD) plans to incorporate SiC electronics on their Long-Life In-situ Solar System Explorer (LLISSE). A prototype is currently being developed for this low-cost concept, which would provide basic, but highly valuable scientific measures from the surface of Venus for months or longer.
Other plans to build a survivable Venus explorer include the Automaton Rover for Extreme Environments (AREE), a “steampunk rover” concept that relies on analog components rather than complex electronic systems. Whereas this concepts seeks to do away with electronics entirely to ensure a Venus mission could operate indefinitely, the new SiC electronics would allow more complex rovers to continue operating in extreme conditions.
Beyond Venus, this new technology could also lead to new classes of probes capable of exploring within gas giants – i.e. Jupiter, Saturn, Uranus and Neptune – where temperature and pressure conditions have been prohibitive in the past. But a probe that relies on a hardened shell and SiC electronic circuits could very well penetrate deep into the interior of these planets and reveal startling new things about their atmospheres and magnetic fields.
The surface of Mercury could also be accessible to rovers and landers using this new technology – even the day-side, where temperatures reach a high of 700 K (427 °C; 800 °F). Here on Earth, there are plenty of extreme environments that could now be explored with the help of SiC circuits. For example, drones equipped with SiC electronics could monitor deep-sea oil drilling or explore deep into the Earth’s interior.
There are also commercial applications involving aeronautical engines and industrial processors, where extreme heat or pressure traditionally made electronic monitoring impossible. Now such systems could be made “smart”, where they are capable of monitoring themselves instead of relying on operators or human oversight.
With extreme circuits and (someday) extreme materials, just about any environment could be explored. Maybe even the interior of a star!
Venus’ atmosphere is as mysterious as it is dense and scorching. For generations, scientists have sought to study it using ground-based telescopes, orbital missions, and the occasional atmospheric probe. And in 2006, the ESA’s Venus Express mission became the first probe to conduct long-term observations of the planet’s atmosphere, which revealed much about its dynamics.
Using this data, a team of international scientists – led by researchers from the Japan Aerospace and Exploration Agency (JAXA) – recently conducted a study that characterized the wind and upper cloud patterns on the night side of Venus. In addition to being the first of its kind, this study also revealed that the atmosphere behaves differently on the night side, which was unexpected.
The study, titled “Stationary Waves and Slowly Moving Features in the Night Upper Clouds of Venus“, recently appeared in the scientific journal Nature Astronomy. Led by Javier Peralta, the International Top Young Fellow of JAXA, the team consulted data obtained by Venus Express’ suite of scientific instruments in order to study the planet’s previously-unseen cloud types, morphologies, and dynamics.
Whereas plenty of studies have been conducted of Venus’ atmosphere from soace, this was the first time that a study was not focused on the dayside of the planet. As Dr. Peralta explained in an ESA press statement:
“This is the first time we’ve been able to characterize how the atmosphere circulates on the night side of Venus on a global scale. While the atmospheric circulation on the planet’s dayside has been extensively explored, there was still much to discover about the night side. We found that the cloud patterns there are different to those on the dayside, and influenced by Venus’ topography.“
Since the 1960s, astronomers have been aware that Venus’ atmosphere behaves much differently that those of other terrestrial planets. Whereas Earth and Mars have atmospheres that co-rotate at approximately the same speed as the planet, Venus’ atmosphere can reach speeds of more than 360 km/h (224 mph). So while the planet takes 243 days to rotate once on its axis, the atmosphere takes only 4 days.
This phenomena, known as “super-rotation”, essentially means that the atmosphere moves over 60 times faster than the planet itself. In addition, measurements in the past have shown that the fastest clouds are located at the upper cloud level, 65 to 72 km (40 to 45 mi) above the surface. Despite decades of study, atmospheric models have been unable to reproduce super-rotation, which indicated that some of the mechanics were unknown.
“We focused on the night side because it had been poorly explored; we can see the upper clouds on the planet’s night side via their thermal emission, but it’s been difficult to observe them properly because the contrast in our infrared images was too low to pick up enough detail.”
This consisted of observing Venus’ night side clouds with the probe’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). The instrument gathered hundreds of images simultaneously and different wavelengths, which the team then combined to improve the visibility of the clouds. This allowed the team to see them properly for the first time, and also revealed some unexpected things about Venus’ night side atmosphere.
What they saw was that atmospheric rotation appeared to be more chaotic on the night side than what has been observed in the past on the dayside. The upper clouds also formed different shapes and morphologies – i.e. large, wavy, patchy, irregular and filament-like patterns – and were dominated by stationary waves, where two waves moving in opposite directions cancel each other out and create a static weather pattern.
The 3D properties of these stationary waves were also obtained by combining VIRTIS data with radio-science data from the Venus Radio Science experiment (VeRa). Naturally, the team was surprised to find these kinds of atmospheric behaviors since they were inconsistent with what has been routinely observed on the dayside. Moreover, they contradict the best models for explaining the dynamics of Venus’ atmosphere.
Known as Global Circulation Models (GCMs), these models predict that on Venus, super-rotation would occur in much the same way on both the dayside and the night side. What’s more, they noticed that stationary waves on the night side appeared to coincide with high-elevation features. As Agustin Sánchez-Lavega, a researcher from the University del País Vasco and a co-author on the paper, explained:
“Stationary waves are probably what we’d call gravity waves–in other words, rising waves generated lower in Venus’ atmosphere that appear not to move with the planet’s rotation. These waves are concentrated over steep, mountainous areas of Venus; this suggests that the planet’s topography is affecting what happens way up above in the clouds.“
This is not the first time that scientists have spotted a possible link between Venus’ topography and its atmospheric motion. Last year, a team of European astronomers produced a study that showed how weather patterns and rising waves on the dayside appeared to be directly connected to topographical features. These findings were based on UV images taken by the Venus Monitoring Camera (VMC) on board the Venus Express.
Finding something similar happening on the night side was something of a surprise, until they realized they weren’t the only ones to spot them. As Peralta indicated:
“It was an exciting moment when we realized that some of the cloud features in the VIRTIS images didn’t move along with the atmosphere. We had a long debate about whether the results were real–until we realised that another team, led by co-author Dr. Kouyama, had also independently discovered stationary clouds on the night side using NASA’s Infrared Telescope Facility (IRTF) in Hawaii! Our findings were confirmed when JAXA’s Akatsuki spacecraft was inserted into orbit around Venus and immediately spotted the biggest stationary wave ever observed in the Solar System on Venus’ dayside.“
These findings also challenge existing models of stationary waves, which are expected to form from the interaction of surface wind and high-elevation surface features. However, previous measurements conducted by the Soviet-era Venera landers have indicated that surface winds might too weak for this to happen on Venus. In addition, the southern hemisphere, which the team observed for their study, is quite low in elevation.
And as Ricardo Hueso of the University of the Basque Country (and a co-author on the paper) indicated, they did not detect corresponding stationary waves in the lower cloud levels. “We expected to find these waves in the lower levels because we see them in the upper levels, and we thought that they rose up through the cloud from the surface,” he said. “It’s an unexpected result for sure, and we’ll all need to revisit our models of Venus to explore its meaning.”
From this information, it seems that topography and elevation are linked when it comes to Venus’ atmospheric behavior, but not consistently. So the standing waves observed on Venus’ night side may be the result of some other undetected mechanism at work. Alas, it seems that Venus’ atmosphere – in particular, the key aspect of super-rotation – still has some mysteries for us.
The study also demonstrated the effectiveness of combining data from multiple sources to get a more detailed picture of a planet’s dynamics. With further improvements in instrumentation and data-sharing (and perhaps another mission or two to the surface) we can expect to get a clearer picture of what is powering Venus’ atmospheric dynamics before long.
With a little luck, there may yet come a day when we can model the atmosphere of Venus and predict its weather patterns as accurately as we do those of Earth.
From space, Venus looks like a big, opaque ball. Thanks to its extremely dense atmosphere, which is primarily composed of carbon dioxide and nitrogen, it is impossible to view the surface using conventional methods. As a result, little was learned about its surface until the 20th century, thanks to development of radar, spectroscopic and ultraviolet survey techniques.
Interestingly enough, when viewed in the ultraviolet band, Venus looks like a striped ball, with dark and light areas mingling next to one another. For decades, scientists have theorized that this is due to the presence of some kind of material in Venus’ cloud tops that absorbs light in the ultraviolet wavelength. In the coming years, NASA plans to send a CubeSat mission to Venus in the hopes of solving this enduring mystery.
The mission, known as the CubeSat UV Experiment (CUVE), recently received funding from the Planetary Science Deep Space SmallSat Studies (PSDS3) program, which is headquartered as NASA’s Goddard Space Flight Center. Once deployed, CUVE will determine the composition, chemistry, dynamics, and radiative transfer of Venus’ atmosphere using ultraviolet-sensitive instruments and a new carbon-nanotube light-gathering mirror.
The mission is being led by Valeria Cottini, a researcher from the University of Maryland who is also CUVE’s Principle Investigator (PI). In March of this year, NASA’s PSDS3 program selected it as one of 10 other studies designed to develop mission concepts using small satellites to investigate Venus, Earth’s moon, asteroids, Mars and the outer planets.
Venus is of particular interest to scientists, given the difficulties of exploring its thick and hazardous atmosphere. Despite the of NASA and other space agencies, what is causing the absorption of ultra-violet radiation in the planet’s cloud tops remains a mystery. In the past, observations have shown that half the solar energy the planet receives is absorbed in the ultraviolet band by the upper layer of its atmosphere – the level where sulfuric-acid clouds exist.
Other wavelengths are scattered or reflected into space, which is what gives the planet its yellowish, featureless appearance. Many theories have been advanced to explain the absorption of UV light, which include the possibility that an absorber is being transported from deeper in Venus’ atmosphere by convective processes. Once it reaches the cloud tops, this material would be dispersed by local winds, creating the streaky pattern of absorption.
The bright areas are therefore thought to correspond to regions that do not contain the absorber, while the dark areas do. As Cottini indicated in a recent NASA press release, a CubeSat mission would be ideal for investigating these possibilities:
“Since the maximum absorption of solar energy by Venus occurs in the ultraviolet, determining the nature, concentration, and distribution of the unknown absorber is fundamental. This is a highly-focused mission – perfect for a CubeSat application.”
Such a mission would leverage recent improvements in miniaturization, which have allowed for the creation of smaller, box-sized satellites that can do the same jobs as larger ones. For its mission, CUVE would rely on a miniaturized ultraviolet camera and a miniature spectrometer (allowing for analysis of the atmosphere in multiple wavelengths) as well as miniaturized navigation, electronics, and flight software.
Another key component of the CUVE mission is the carbon nanotube mirror, which is part of a miniature telescope the team is hoping to include. This mirror, which was developed by Peter Chen (a contractor at NASA Goddard), is made by pouring a mixture of epoxy and carbon nanotubes into a mold. This mold is then heated to cure and harden the epoxy, and the mirror is coated with a reflective material of aluminum and silicon dioxide.
In addition to being lightweight and highly stable, this type of mirror is relatively easy to produce. Unlike conventional lenses, it does not require polishing (an expensive and time-consuming process) to remain effective. As Cottini indicated, these and other developments in CubeSat technology could facilitate low-cost missions capable of piggy-backing on existing missions throughout the Solar System.
“CUVE is a targeted mission, with a dedicated science payload and a compact bus to maximize flight opportunities such as a ride-share with another mission to Venus or to a different target,” she said. “CUVE would complement past, current, and future Venus missions and provide great science return at lower cost.”
The team anticipates that in the coming years, the probe will be sent to Venus as part of a larger mission’s secondary payload. Once it reaches Venus, it will be launched and assume a polar orbit around the planet. They estimate that it would take CUVE one-and-a-half years to reach its destination, and the probe would gather data for a period of about six months.
If successful, this mission could pave the way for other low-cost, lightweight satellites that are deployed to other Solar bodies as part of a larger exploration mission. Cottini and her colleagues will also be presenting their proposal for the CUVE satellite and mission at the 2017 European Planetary Science Congress, which is being held from September 17th – 22nd in Riga, Latvia.