Image from NASA's Mariner 10 spacecraft in February 1974 as it traveled away from Venus. (Credit: NASA/JPL-Caltech)
The surface of Venus is like a scene from Dante’s Inferno – “Abandon all hope, ye who enter here!” and so forth. The temperature is hot enough to melt lead, the air pressure is almost one hundred times that of Earth’s at sea level, and there are clouds of sulfuric acid rain to boot! But roughly 48 to 60 km (30 to 37.3 mi) above the surface, the temperatures are much cooler, and the air pressure is roughly equal to Earth’s at sea level. As such, scientists have speculated that life could exist above the cloud deck (possibly in the form of microbes) as it does on Earth.
Unfortunately, these clouds are not composed of water but of concentrated sulfuric acid, making the likelihood that life could survive among them doubtful. However, a new study led by scientists from the Massachusetts Institute of Technology (MIT) reveals that the basic building blocks of life (nucleic acid bases) are stable in concentrated sulfuric acid. These findings indicate that Venus’ atmosphere could support the complex chemistry needed for life to survive, which could have profound implications in the search for habitable planets and extraterrestrial life.
Image of Venus taken by NASA’s Pioneer-Venus Orbiter in 1979. (Credit: NASA)
A recent study published in Astrobiology examines the likelihood of the planet Venus being able to support life within the thick cloud layer that envelopes it. This study holds the potential to help us better understand how life could exist under the intense Venusian conditions, as discussions within the scientific community about whether life exists on the second planet from the Sun continue to burn hotter than Venus itself.
In a recent study published in Instrumentation and Methods for Astrophysics, the private space company, Rocket Lab, outlines a plan to send their high-energy Photon spacecraft to Venus in May 2023 with the primary goal of searching for life within the Venusian atmosphere. The planet Venus has become a recent hot topic in the field of astrobiology, which makes the high-energy Photon mission that much more exciting.
Rocket Lab hopes to build off their recent successful launch of the CAPSTONE mission using its Photon satellite bus, and consists of a CubeSat designed to study the near rectilinear halo orbit (NRHO) around the Moon and its applications for long-term missions such as Gateway.
Jupiter from Juno Perijove 29 - NASA/JPL/Kevin Gil
For decades, scientists engaged in the search for life in the Universe (aka. astrobiology) have focused on searching for life on other Earth-like planets. These included terrestrial (aka. rocky) planets beyond our Solar System (extrasolar planets) and ones here at home. Beyond Earth, Mars is considered to be the most habitable planet next to Earth, and scientists have also theorized that life could exist (in microbial form) in the cloud tops of Venus.
In all cases, a major focal point is whether or not planets have large bodies of water on their surfaces (or did in the past). However, a new study led by a research team from the UK and German (with support from NASA) has shown that the existence of life may have less to do with the quantity of water and more to with the presence of atmospheric water molecules. As a result, we may have better luck finding life on Jupiter’s turbulent cloud deck than Venus’.
The planet Venus, as imaged by the Magellan mission. Credit: NASA/JPL
Venus is unique—almost—in our Solar System because it’s what’s known as a “super-rotator.” That means that Venus’ atmosphere rotates faster than the planet itself. Only Saturn’s moon Titan has the same characteristic.
Scientists have been trying to figure out what causes this super-rotation, and now an international team of researchers might have figured it out.
The spacecraft would circumnavigate Venus every four to six days, with solar panels charging every two to three days on the side of planet illuminated by the sun. Credit: CRASH Lab, University at Buffalo.
Venus is colloquially referred to as “Earth’s Twin”, owing to the similarities it has with our planet. Not surprisingly though, there is a great deal that scientists don’t know about Venus. Between the hot and hellish landscape, extremely thick atmosphere, and clouds of sulfuric rain, it is virtually impossible to explore the planet’s atmosphere and surface. What’s more, Venus’ slow rotation makes the study of its “dark side” all the more difficult.
However, these challenges have spawned a number of innovative concepts for exploration. One of these comes from the University of Buffalo’s Crashworthiness for Aerospace Structures and Hybrids (CRASH) Laboratory, where researchers are designing a unique concept known as the Bio-inspired Ray for Extreme Environments and Zonal Explorations (BREEZE).
Artist's conception of a terraformed Venus, showing a surface largely covered in oceans. Credit: Wikipedia Commons/Ittiz
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”.
According to a new study, microbial life could exist in Venus' cloud tops, where temperature and pressure conditions are favorable. Credit: NASA
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.
A composite image of the planet Venus as seen by the Japanese probe Akatsuki. The clouds of Venus could have environmental conditions conducive to microbial life. Credit: JAXA/Institute of Space and Astronautical Science
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.
Aircraft like the Venus Atmospheric Maneuverable Platform (VAMP) could explore the cloud tops of Venus for possible signs of life. Credit: Northrop Grumman Corp
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.
The cloud-enshrouded Venus appears featureless, as shown in this image taken by NASA’s MESSENGER mission. In ultraviolet, however, the planet takes on a completely different appearance as seen below. Credits: NASA
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.
Ultraviolet image of Venus taken by NASA’s Pioneer-Venus Orbiter in 1979, lending Venus a striped, light and dark appearance. Credit: NASA
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.”
CubeSats being deployed from the International Space Station during Expedition 47. Image: NASA
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.”
A cubesat structure, 1U in size. Credit: Wikipedia Commons/Svobodat
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.
Welcome back to our planetary weather series! Today, we look at Earth’s overheated “sister planet”, Venus!
Venus is often called Earth’s “Sister Planet” because of all the things they have in common. They are comparable in size, have similar compositions, and both orbit within the Sun’s habitable zone. But beyond that, there are some notable differences that makes Venus a molten hellhole, and about the last place anyone would want to visit!
Much of this has to do with Venus’ atmosphere, which is incredibly dense and entirely hostile to life as we know it. And because of its natural density and composition, the average surface temperature of Venus is hot enough to melt lead. All of this adds up to some pretty interesting weather patterns, which are also incredibly hostile!
Venus Atmosphere:
Although carbon dioxide is invisible, the clouds on Venus are made up of opaque clouds of sulfuric acid, so we can’t see down to the surface using conventional methods. Everything we know about the surface of Venus has been gathered by spacecraft equipped with radar imaging instruments, which can peer through the dense clouds and reveal the surface below.
From the many flybys and atmospheric probes sent into its thick clouds, scientists have learned that Venus’ atmosphere is incredibly dense. In fact, the mass of Venus atmosphere is 93 times that of Earth’s, and the air pressure at the surface is estimated to be as high as 92 bar – i.e. 92 times that of Earth’s at sea level. If it were possible for a human being to stand on the surface of Venus, they would be crushed by the atmosphere.
The composition of the atmosphere is extremely toxic, consisting primarily of carbon dioxide (96.5%) with small amounts of nitrogen (3.5%) and traces of other gases – most notably sulfur dioxide. Combined with its density, the composition generates the strongest greenhouse effect of any planet in the Solar System.
It is also the hottest planet in the Solar System, experiencing mean surface temperatures of 735 K (462 °C; 863.6 °F). Above the dense CO² layer, thick clouds consisting mainly of sulfur dioxide and sulfuric acid droplets scatter about 90% of the sunlight back into space.
The planet is also isothermal, which means that there is little variation in Venus’ surface temperature between day and night, or the equator and the poles. The planet’s minute axial tilt – less than 3° compared to Earth’s 23.5° – and its very slow rotational period (the planet takes around 243 days to complete a single rotation) also minimizes seasonal temperature variation.
Artist’s impression of the surface of Venus. Credit: ESA/AOES
The only appreciable variation in temperature occurs with altitude. The highest point on Venus, Maxwell Montes, is therefore the coolest point on the planet, with a temperature of about 655 K (380 °C; 716 °F) and an atmospheric pressure of about 4.5 MPa (45 bar).
Meteorological Phenomena:
The weather on Venus is one of the aspects of the planet under constant study from Earth-based telescopes and space missions to Venus. And from what we’ve seen, the weather on Venus is very extreme. The entire atmosphere of the planet circulates around quickly, with winds reaching speeds of up to 85 m/s (300 km/h; 186.4 mph) at the cloud tops, which circle the planet every four to five Earth days.
At this speed, these winds move up to 60 times the speed of the planet’s rotation, whereas Earth’s fastest winds are only 10-20% of the planet’s rotational speed. Spacecraft equipped with ultraviolet imaging instruments are able to observe the cloud motion around Venus, and see how it moves at different layers of the atmosphere. The winds blow in a retrograde direction, and are the fastest near the poles.
Closer to the equator, the wind speeds die down to almost nothing. Because of the thick atmosphere, the winds move much slower as you get close to the surface of Venus, reaching speeds of about 5 km/h. Because it’s so thick, though, the atmosphere is more like water currents than blowing wind at the surface, so it is still capable of blowing dust around and moving small rocks across the surface of Venus.
Over the past six years wind speeds in Venus’ atmosphere have been steadily rising (ESA
Several flybys past the planet have also indicated that its dense clouds are capable of producing lightning, much like the clouds on Earth. Their intermittent appearance indicates a pattern associated with weather activity, and the lightning rate is at least half of that on Earth. Since Venus does not experience rainfall (except in the form of sulfuric acid), it has been theorized that the lightning is being caused by a volcanic eruption.
What is the weather like on Venus? Terrible, would be the short answer. The long answer is that it is extremely hot, the air pressure is extremely high, there are very strong winds, sulfuric acid rain (at higher altitudes) and lightning storms driven by volcanic eruptions. It is little wonder then why the only practical option for colonizing Venus involves creating floating cities above the cloud layer.
