The changing phases of Venus, from the 2013 apparition. Credit and copyright: Shahrin Ahmad (@Shahgazer)
Venus returns – The changing phases of Venus, from the 2013 apparition. Credit and copyright: Shahrin Ahmad (@Shahgazer)
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.
Not all elongations of Mercury or Venus are equal, but depend on the seasonal angle of the ecliptic, and whether they occur near aphelion or perihelion. Credit: Dave Dickinson
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.
The Moon, Venus and Mercury – looking west at dusk on March 18th. Credit: Stellarium
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:
Venus in the ultraviolet courtesy of JAXA’s Akatsuki spacecraft. Credit: JAXA/Akatsuki/ISAS/DARTS/Damia Bouic
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.
SiC high-temperature electronics before and after testing in Venus surface conditions (rugged operation for extended durations). Credits: Marvin Smith/David Spry/NASA GRC
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.
AREE is a clockwork rover inspired by mechanical computers. A JPL team is studying how this kind of rover could explore extreme environments, like the surface of Venus. Credit: NASA/JPL-Caltech
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!
Artist's impression of the Venus Express spacecraft in orbit around Venus. Credit: ESA
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.
The atmospheric super-rotation at the upper clouds of Venus. While the super-rotation is present in both day and night sides of Venus, it seems more uniform in the day. Credits: JAXA, ESA, J. Peralta and R. Hueso.
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.
As such, Peralta and his international team – which included researchers from the Universidad del País Vasco in Spain, the University of Tokyo, the Kyoto Sangyo University, the Center for Astronomy and Astrophysics (ZAA) at Berlin Technical University, and the Institute of Astrophysics and Space Planetology in Rome – chose to look at the unexplored side to see what they could find. As he described it:
“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.
Examples of new types of cloud morphology discovered on the night side of Venus thanks to Venus Express (ESA) and the infrared telescope IRTF (NASA). Credits: ESA/NASA/J. Peralta and R. Hueso.
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.
Schematic illustration of the proposed behaviour of gravity waves in the vicinity of mountainous terrain on Venus. Credit: ESA
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.”
Artist’s impression of Venus Express performing aerobreaking maneuvers in the planet’s atmosphere in June and July 2014. Credit: ESA–C. Carreau
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.
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.
In 2005, the Future In-Space Operations Working Group (FISOWG) was established with the help of NASA to assess how advances in spaceflight technologies could be used to facilitate missions back to the Moon and beyond. In 2006, the FISO Working Group also established the FISO Telecon Series to conduct outreach to the public and educate them on issues pertaining to spaceflight technology, engineering, and science.
Every week, the Telecon Series holds a seminar where experts are able to share the latest news and developments from their respective fields. On Wednesday, April 19th, in a seminar titled “An Air-Breathing Metal-Combustion Power Plant for Venus in situ Exploration“, NASA engineer Michael Paul presented a novel idea where existing technology could be used to make longer-duration missions to Venus.
To recap the history of Venus exploration, very few probes have ever been able to explore its atmosphere or surface for long. Not surprising, considering that the atmospheric pressure on Venus is 92 times what it is here on Earth at sea level. Not to mention the fact that Venus is also the hottest planet in the Solar System – with average surface temperatures of 737 K (462 °C; 863.6 °F).
Although similar in size and composition to the Earth, Venus has an extremely dense atmosphere with clouds that produce sulfuric acid rain. Credit: NASA
Hence why those few probes that actually explored the atmosphere and surface in detail – like the Soviet-era Venera probes and landers and NASA’s Pioneer Venus multiprobe – were only able to return data for a matter of hours. All other missions to Venus have either taken the form of orbiters or consisted of spacecraft conducting flybys while en route to other destinations.
Having worked in the fields of space exploration and aerospace engineering for 20 years, Michael Paul is well-versed in the challenges of mounting missions to other planets. During his time with the John Hopkins University Applied Physics Laboratory (JHUAPL), he contributed to NASA’s Contour and Stereo missions, and was also instrumental in the launch and early operations of the MESSENGER mission to Mercury.
However, it was a flagship-level study in 2008 – performed collaboratively between JHUAPL and NASA’s Jet Propulsion laboratory (JPL) – that opened his eyes to the need for missions that took advantage of the process known as In-Situ Resource Utilization (ISRU). As he stated during the seminar:
“That year we actually studied a very large mission to Europa which evolved into the current Europa Clipper mission. And we also studied a flagship mission to the Saturn, to Titan specifically. The Titan-Saturn system mission study was a real eye-opener for me in terms what could be done and why we should be doing a lot of more adventurous and more aggressive exploration of in-situ in certain places.”
The flagship mission to Titan was the subject of Paul’s work since joining Penn Sate’s Applied Research Laboratory in 2009. During his time there, he became a NASA Innovative Advanced Concepts Program (NIAC) Fellow for his co-creation of the Titan Submarine. For this mission, which will explore the methane lakes of Titan, Paul helped to develop underwater power systems that would provide energy for planetary landers that can’t see the Sun.
Having returned to JHUAPL, where he is now the Space Mission Formulation Lead, Paul continues to work on in-situ concepts that could enable missions to locations in the Solar System that present a challenge. In-situ exploration, where local resources are relied upon for various purposes, presents numerous advantages over more traditional concepts, not the least of which is cost-effectiveness.
Consider mission that rely on Multi-Mission Radioisotope Thermoelectric Generators (MMRTG) – where radioactive elements like Plutonium-238 are used to generate electricity. Whereas this type of power system – which was used by the Viking 1 and 2 landers (sent to Mars in 1979) and the more recent Curiosity rover – provides unparalleled energy density, the cost of such missions is prohibitive.
What’s more, in-situ missions could also function in places where conventional solar cells would not work. These include not only locations in the outer Solar System (i.e. Europa,Titan and Enceladus) but also places closer to home. The South Pole-Aitken Basin, for example, is a permanently shadowed location on the Moon that NASA and other space agencies are interesting in exploring (and maybe colonizing) due to the abundance of water ice there.
But there’s also the surface Venus, where sunlight is in short supply because of the planet’s dense atmosphere. As Paul explained in the course of the seminar:
“What can you do with other power systems in places where the Sun just doesn’t shine? Okay, so you want to get to the surface of Venus and last more than a couple of hours. And I think that in the last 10 or 15 years, all the missions that [were proposed] to the surface of Venus pretty much had a two-hour timeline. And those were all proposed, none of those missions were actually flown. And that’s in line with the 2 hours that the Russian landers survived when they got there, to the surface of Venus.”
Diagram of a Sterling Engine, part of proposed mission to Europe (“Fire on Europa”). Credit: lpi.usra.edu
The solution to this problem, as Paul sees it, is to employ a Stored-Chemical Energy and Power System (SCEPS), also known as a Sterling engine. This proven technology relies on stored chemical energy to generate electricity, and is typically used in underwater systems. But repurposed for Venus, it could provide a lander mission with a considerable amount of time (compared to previous Venus missions) with which to conduct surface studies.
For the power system Paul and his colleagues are envisioning, the Sterling engine would take solid-metal lithium (or possibly solid iodine), and then liquefy it with a pyrotechnic charge. This resulting liquid would then be fed into another chamber where it would combined with an oxidant. This would produce heat and combustion, which would then be used to boil water, spin turbines, and generate electricity.
Such a system is typically closed and produces no exhaust, which makes it very useful for underwater systems that cannot compromise their buoyancy. On Venus, such a system would allow for electrical production without short-lived batteries, an expensive nuclear fuel cell, and could function in a low solar-energy environment.
An added benefit for such a craft operating on Venus is that the oxidizer would be provided locally, thus removing the need for an heavy component. By simply letting in outside CO2 – which Venus’ atmosphere has in abundance – and combining with the system’s liquified lithium (or iodine), the SCEPS system could provide sustained energy for a period of days.
The Advanced Lithium Ion Venus Explorer (ALIVE), derived from the COMPASS final report (2016). Credit: Oleson, Steven R., and Michael Paul.
Further help came from the Glenn Research Center’s COMPASS lab, were engineers from multiple disciplines performs integrated vehicle systems analyses. From all of this, a mission concept known as the Advanced Lithium Venus Explorer (ALIVE) was developed. With the help of Steven Oleson – the head of GRC’s COMPASS lab – Paul and his team envision a mission where a lander would reach the surface of Venus and study it for 5 to 10 days.
All told, that’s an operational window of between 120 and 240 hours – in other words, 60 to 120 times as long as previous missions. However, how much such a mission would cost remains to be seen. According to Paul, that question became the basis of an ongoing debate between himself and Oleson, who disagreed as to whether it would be part of the Discovery Program or the New Frontiers Program.
As Paul explained, missions belonging to the former were recently capped at the $450 to $500 million level while the latter are capped at $850 million. “I believe that if you did this right, you could get it into a Discovery mission,” he said. “Here at APL, I’ve seen really complicated ideas fit inside a Discovery cost cap. And I believe that the way we crafted this mission, you could do this for a Discovery mission. And it would be really exciting to get that done.”
Artist’s impression of the surface of Venus. Credit: ESA/AOES
From a purely technological standpoint, this not a new idea. But in terms of space exploration, it has never been done before. Granted, there are still many tests which would need to be conducted before any a mission to Venus can be planned. In particular, there are the byproducts created by combusting lithium and CO2 under Venus-like conditions, which already produced some unexpected results during tests.
In addition, there is the problem of nitrogen gas (N2) – also present in Venus’ atmosphere – building up in the system, which would need to be vented in order to prevent a blowout. But the advantages of such a system are evident, and Paul and his colleagues are eager to take additional steps to develop it. This summer, they will be doing another test of a lithium SCEPS under the watchful eye of NAIC.
By this time next year, they hope to have completed their analysis and their design for the system, and begin building one which they hope to test in a controlled temperature environment. This will be the first step in what Paul hopes will be a three-year period of testing and development.
“The first year we’re basically going to do a lot of number crunching to make sure we got it right,” he said. “The second year we’re going to built it, and test it at higher temperatures than room temperature – but not the high temperatures of Venus! And in the third year, we’re going to do the high temperature test.”
Ultimately, the concept could be made to function in any number of high and low temperature conditions, allowing for cost-effective long-duration missions in all kinds of extreme environments. These would include Titan, Europa and Enceladus, but also Venus, the Moon, and perhaps the permanently-shadowed regions on Mercury’s poles as well.
Space exploration is always a challenge. Whenever ideas come along that make it possible to peak into more environments, and on a budget to boot, it is time to start researching and developing them!
Beads of rainwater on a poplar leaf act like lenses, focusing light and enlarging the leaf’s network of veins. Moving at 186,000 miles per second, light from the leaf arrives at your eye 0.5 nanosecond later. A blink of an eye takes 600,000 times as much time! Credit: Bob King
My attention was focused on beaded water on a poplar leaf. How gemmy and bursting with the morning’s sunlight. I moved closer, removed my glasses and noticed that each drop magnified a little patch of veins that thread and support the leaf.
Focusing the camera lens, I wondered how long it took the drops’ light to reach my eye. Since I was only about six inches away and light travels at 186,000 miles per second or 11.8 inches every billionth of a second (one nanosecond), the travel time amounted to 0.5 nanoseconds. Darn close to simultaneous by human standards but practically forever for positronium hydride, an exotic molecule made of a positron, electron and hydrogen atom. The average lifetime of a PsH molecule is just 0.5 nanoseconds.
Light takes about 35 microseconds to arrive from a transcontinental jet and its contrail. Credit: Bob King
In our everyday life, the light from familiar faces, roadside signs and the waiter whose attention you’re trying to get reaches our eyes in nanoseconds. But if you happen to look up to see the tiny dark shape of a high-flying airplane trailed by the plume of its contrail, the light takes about 35,000 nanoseconds or 35 microseconds to travel the distance. Still not much to piddle about.
The space station orbits the Earth in outer space some 250 miles overhead. During an overhead pass, light from the orbiting science lab fires up your retinas 1.3 milliseconds later. In comparison, a blink of the eye lasts about 300 milliseconds (1/3 of a second) or 230 times longer!
The Lunar Laser Ranging Experiment placed on the Moon by the Apollo 14 astronauts. Observatories beam a laser to the small array, which reflects a bit of the light back. Measuring the time delay yields the Moon’s distance to within about a millimeter. At the Moon’s surface the laser beam spreads out to 4 miles wide and only one photon is reflected back to the telescope every few seconds. Credit: NASA
Light time finally becomes more tangible when we look at the Moon, a wistful 1.3 light seconds away at its average distance of 240,000 miles. To feel how long this is, stare at the Moon at the next opportunity and count out loud: one one thousand one. Retroreflecting devices placed on the lunar surface by the Apollo astronauts are still used by astronomers to determine the moon’s precise distance. They beam a laser at the mirrors and time the round trip.
Venus as a super-thin crescent only 10 hours before conjunction on March 25. The planet was just 2.3 light minutes from the Earth at the time. Credit: Shahrin Ahmad
Of the eight planets, Venus comes closest to Earth, and it does so during inferior conjunction, which coincidentally occurred on March 25. On that date only 26.1 million miles separated the two planets, a distance amounting to 140 seconds or 2.3 minutes — about the time it takes to boil water for tea. Mars, another close-approaching planet, currently stands on nearly the opposite side of the Sun from Earth.
With a current distance of 205 million miles, a radio or TV signal, which are both forms of light, broadcast to the Red Planet would take 18.4 minutes to arrive. Now we can see why engineers pre-program a landing sequence into a Mars’ probe’s computer to safely land it on the planet’s surface. Any command – or change in commands – we might send from Earth would arrive too late. Once a lander settles on the planet and sends back telemetry to communicate its condition, mission control personnel must bite their fingernails for many minutes waiting for light to limp back and bring word.
Before we speed off to more distant planets, let’s consider what would happen if the Sun had a catastrophic malfunction and suddenly ceased to shine. No worries. At least not for 8.3 minutes, the time it takes for light, or the lack of it, to bring the bad news.
Pluto and Charon lie 3.1 billion miles from Earth, a long way for light to travel. We see them as they were more than 4 hours ago. NASA/JHUAPL/SwRI
Light from Jupiter takes 37 minutes to reach Earth; Pluto and Charon are so remote that a signal from the “double planet” requires 4.6 hours to get here. That’s more than a half-day of work on the job, and we’ve only made it to the Kuiper Belt.
Let’s press on to the nearest star(s), the Alpha Centauri system. If 4.6 hours of light time seemed a long time to wait, how about 4.3 years? If you think hard, you might remember what you were up to just before New Year’s Eve in 2012. About that time, the light arriving tonight from Alpha Centauri left that star and began its earthward journey. To look at the star then is to peer back in time to late 2012.
The Summer Triangle rises fully in the eastern sky around 3 o’clock in the morning in late March. Created with Stellarium
But we barely scrape the surface. Let’s take the Summer Triangle, a figure that will soon come to dominate the eastern sky along with the beautiful summer Milky Way that appears to flow through it. Altair, the southernmost apex of the triangle is nearby, just 16.7 light years from Earth; Vega, the brightest a bit further at 25 and Deneb an incredible 3,200 light years away.
We can relate to the first two stars because the light we see on a given evening isn’t that “old.” Most of us can conjure up an image of our lives and the state of world affairs 16 and 25 years ago. But Deneb is exceptional. Photons departed this distant supergiant (3,200 light years) around the year 1200 B.C. during the Trojan War at the dawn of the Iron Age. That’s some look-back time!
Rho Cassiopeia, currently at magnitude +4.5, is one of the most distant stars visible with the naked eye. Its light requires about 8,200 years to reach our eyes. This star, a variable, is enormous with a radius about 450 times that of the Sun. Credit: IAU/Sky and Telescope (left); Anynobody, CC BY-SA 3.0 / Wikipedia
One of the most distant naked eye stars is Rho Cassiopeiae, yellow variable some 450 times the size of the Sun located 8,200 light years away in the constellation Cassiopeia. Right now, the star is near maximum and easy to see at nightfall in the northwestern sky. Its light whisks us back to the end of the last great ice age at a time and the first cave drawings, more than 4,000 years before the first Egyptian pyramid would be built.
This is the digital message (annotated here) sent by Frank Drake to M13 in 1974 using the Arecibo radio telescope.
On and on it goes: the nearest large galaxy, Andromeda, lies 2.5 million light years from us and for many is the faintest, most distant object visible with the naked eye. To think that looking at the galaxy takes us back to the time our distant ancestors first used simple tools. Light may be the fastest thing in the universe, but these travel times hint at the true enormity of space.
Let’s go a little further. On November 16, 1974 a digital message was beamed from the Arecibo radio telescope in Puerto Rico to the rich star cluster M13 in Hercules 25,000 light years away. The message was created by Dr. Frank Drake, then professor of astronomy at Cornell, and contained basic information about humanity, including our numbering system, our location in the solar system and the composition of DNA, the molecule of life. It consisted of 1,679 binary bits representing ones and zeroes and was our first deliberate communication sent to extraterrestrials. Today the missive is 42 light years away, just barely out the door.
Galaxy GN-z11, shown in the inset, is seen as it was 13.4 billion years in the past, just 400 million years after the big bang, when the universe was only three percent of its current age. The galaxy is ablaze with bright, young, blue stars, but looks red in this image because its light has been stretched to longer spectral wavelengths by the expansion of the universe. Credit: NASA, ESA, P. Oesch, G. Brammer, P. van Dokkum, and G. Illingworth
Let’s end our time machine travels with the most distant object we’ve seen in the universe, a galaxy named GN-z11 in Ursa Major. We see it as it was just 400 million years after the Big Bang (13.4 billion years ago) which translates to a proper distance from Earth of 32 billion light years. The light astronomers captured on their digital sensors left the object before there was an Earth, a Solar System or even a Milky Way galaxy!
Thanks to light’s finite speed we can’t help but always see things as they were. You might wonder if there’s any way to see something right now without waiting for the light to get here? There’s just one way, and that’s to be light itself.
From the perspective of a photon or light particle, which travels at the speed of light, distance and time completely fall away. Everything happens instantaneously and travel time to anywhere, everywhere is zero seconds. In essence, the whole universe becomes a point. Crazy and paradoxical as this sounds, the theory of relativity allows it because an object traveling at the speed of light experiences infinite time dilation and infinite space contraction.
Just something to think about the next time you meet another’s eyes in conversation. Or look up at the stars.
Venus, just 10.5 hours before inferior conjunction on March 25th. Image credit and copyright: Shahrin Ahmad (@Shahgazer)
Venus just 10.5 hours before inferior conjunction on March 25th. Image credit and copyright: Shahrin Ahmad (@Shahgazer)
Have you seen it yet? An old friend greeted us on an early morning run yesterday as we could easily spy brilliant Venus in the dawn, just three days after inferior conjunction this past Saturday on March 25th.
This was an especially wide pass, as the planet crossed just over eight degrees (that’s 16 Full Moon diameters!) north of the Sun. We once managed to see Venus with the unaided eye on the very day of inferior conjunction back in 1998 from the high northern latitudes of the Chena Flood Channel just outside of Fairbanks, Alaska.
The planet was a slender 59.4” wide, 1% illuminated crescent during this past weekend’s passage, and the wide pass spurred many advanced imagers to hunt for the slim crescent in the daytime sky. Of course, such a feat is challenging near the dazzling daytime Sun. Safely blocking the Sun out of view and being able to precisely point your equipment is key in this endeavor. A deep blue, high contrast sky helps, as well. Still, many Universe Today readers rose to the challenge of chronicling the horns of the slender crescent Venus as they rotated ’round the limb and the nearby world moved once again from being a dusk to dawn object.
A daily sequence showing the ‘Horns of Venus’ rotate as it approaches inferior conjunction. Image credit and copyright: Shahrin Ahmad (@ShahGazer)
The orbit of Venus is tilted 3.4 degrees with respect to the Earth, otherwise, we’d get a transit of the planet like we did on June 5-6th, 2012 once about every 584 days, instead of having to wait again until next century on December 10th, 2117.
The joint NASA/European Space Agency’s SOlar Heliospheric Observatory (SOHO) mission also spied the planet this past weekend as it just grazed the 15 degree wide field of view of its Sun-observing LASCO C3 camera:
The glow of Venus (arrowed) just barely bleeding over into the field of view of SOHO’s LASCO C3 camera. Credit: SOHO/NASA/LASCO
Venus kicks off April as a 58” wide, 3% illuminated crescent and ends the month at 37” wide, fattening up to 28% illumination. On closest approach, the planet presents the largest apparent planetary disk possible as seen from the Earth. Can you see the horns? They’re readily readily apparent even in a low power pair of hunting binoculars. The coming week is a great time to try and see a crescent Venus… with the naked eye. Such an observation is notoriously difficult, and right on the edge of possibility for those with keen eyesight.
One problem for seasoned observers is that we know beforehand that (spoiler alert) that the Horns of Venus, like the Moon, always point away from the direction of the Sun.
True Story: a five year old girl at a public star party once asked me “why does that ‘star’ look like a tiny Moon” (!) This was prior to looking at the planet through a telescope. Children generally have sharper eyes than adults, as the lenses of our corneas wear down and yellow from ultraviolet light exposure over the years.
Still, there are tantalizing historical records that suggest that ancient cultures such as the Babylonians knew something of the true crescent nature of Venus in pre-telescopic times as well.
The Babylonian frieze of Kudurru Melishipak on display at the Louvre, depicting the Sun Moon and Venus. According to some interpretations, the goddess Ishtar (Venus) is also associated with a crescent symbol… possibly lending credence to the assertion that ancient Babylonian astronomers knew something of the phases of the planet from direct observation. Credit: Wikimedia Commons/Image in the Public Domain.
Another fun challenge in the coming months is attempting to see Venus in the daytime. This is surprisingly easy, once you know exactly where to look for it. A nearby crescent Moon is handy, as occurs on April 23rd, May 22nd, and June 20th.
Venus (arrowed) near the daytime Moon. Photo by author.
Strangely enough, the Moon is actually darker than dazzling Venus in terms of surface albedo. The ghostly daytime Moon is just larger and easier to spot. Many historical ‘UFO’ sightings such as a ‘dazzling light seen near the daytime Moon’ by the startled residents of Saint-Denis, France on the morning on January 13th, 1589 were, in fact, said brilliant planet.
The Moon near Venus on May 22nd. Credit: Stellarium.
Venus can appear startlingly bright to even a seasoned observer. We’ve seen the planet rise as a shimmering ember against a deep dark twilight sky from high northern latitudes. Air traffic controllers have tried in vain to ‘hail’ Venus on more than one occasion, and India once nearly traded shots with China along its northern border in 2012, mistaking a bright conjunction of Jupiter and Venus for spy drones.
The third brightest object in the sky behind the Sun and the Moon, Venus is even bright enough to cast a shadow as seen from a dark sky site, something that can be more readily recorded photographically.
Watch our nearest planetary neighbor long enough, and it will nearly repeat the same pattern for a given apparition. This is known as the eight year cycle of Venus, and stems from the fact that 13 Venusian orbits (8x 224.8 days) very nearly equals eight Earth years.
Follow Venus through the dawn in 2017, and it will eventually form a right triangle with the Earth and the Sun on June 3rd, reaching what is known as greatest elongation. This can vary from 47.2 to 45.4 degrees from the Sun, and this year reaches 45.9 degrees elongation in June. The planet then reaches half phase known as dichotomy around this date, though observed versus theoretical dichotomy can vary by three days. The cause of this phenomenon is thought to be the refraction of light in Venus’ dense atmosphere, coupled with observer bias due to the brilliance of Venus itself. When do you see it?
Also, keep an eye out for the ghostly glow on the night-side of Venus, known as Ashen Light. Long thought to be another trick of the eye, there’s good evidence to suggest that this long reported effect actually has a physical basis, though Venus has no large reflecting moon nearby… how could this be? The leading candidate is now thought to be air-glow radiating from the cooling nighttime side of the planet.
Cloud enshrouded Venus held on to its secrets, right up until the Space Age less than a century ago… some observers theorized that the nighttime glow on Venus was due to aurorae, volcanoes or even light pollution from Venusian cities (!). This also fueled spurious sightings of the alleged Venusian moon Neith right up through the 19th century.
Venus should also put in a showing 34 degrees west of the Sun shining at magnitude -4 during the August 21st, 2017 total solar eclipse. Follow that planet, as it makes a complex meet up with Mars, Mercury, and the Moon in late September of this year.
More to come!
-Read about planets, occultations, comets and more for the year in our 101 Astronomical Events for 2017, out as a free e-book from Universe Today.
On June 5th, 2012, the NASA/JAXA Hinode mission captured these stunning views of the transit of Venus. Credit: JAXA/NASA/Lockheed Martin
Earth and Venus are often called “sister planets” because they share some key characteristics. Like Earth, Venus is a terrestrial planet (i.e. composed of silicate minerals and metals) and orbits within our Sun’s habitable zone. But of course, they are also some major differences between them, like the fact that Venus’ is atmosphere is extremely dense and the hottest in the Solar System.
This is particularly interesting when you consider that Venus is not the closest planet to our Sun (that would be Mercury). In fact, its distance from the Sun is just over 70% the distance between Earth and the Sun. And due to its low eccentricity, there is very little variation in its distance during the course of its orbital period.
Perihelion and Aphelion:
While all planets follow an elliptical orbit, Venus’s orbit is the least eccentric of any of the Solar Planets. In fact, with an eccentricity of just 0.006772 , its orbit is the closest to being circular of any of the planets. It’s average distance (semi-major axis) from the Sun is 108,208,000 km (67,237,334 mi), and ranges from 107,477,000 km (66,783,112 mi) at perihelion to 108,939,000 km (67,691,556 mi) at aphelion.
Earth and Venus’ orbit compared. Credit: Sky and Telescope
To put it another way, Venus orbits the Sun at an average distance of 0.723 AU, which ranges from 0.718 AU at its closest to 0.728 AU at its farthest. Compare this to Earth’s eccentricity of 0.0167, which means that it orbits the Sun at an average distance of 1 AU, and that this distance ranges between 0.983 and 1.0167 AUs during its orbital period.
To express that in precise terms, the Earth orbits the Sun at an average distance of 149,598,023 km (92,955,902 mi), and varies between a distance of 147,095,000 km (91,401,000 mi) at perihelion to a distance of 152,100,000 km (94,500,000 mi) at aphelion.
Mars, by contrast, orbits the Sun at an average distance of 227,939,200 km (141,634,852 mi), or 1.52 AU. But due to its high eccentricity of 0.0934, it ranges from a distance of 206,700,000 km (128,437,425 mi) at perihelion to 249,200,000 km (154,845,700 mi) at aphelion – or between 1.38 to 1.666 AUs.
Mercury, meanwhile, has the highest eccentricity of any planet in the Solar System – a surprising 0.2056. While it’s average distance from the Sun is 57,909,050 km (35,983,015 mi), or 0.387 AU, it ranges from 46,001,200 km (28,583,820 mi) at perihelion to 69,816,900 km (43,382,210 mi) at aphelion – or 0.3075 to 0.4667 AUs.
Animated diagram showing the spacing of the Solar Systems planet’s, the unusually closely spaced orbits of six of the most distant KBOs, and the possible “Planet 9”. Credit: Caltech/nagualdesign
Hence, you might say Venus is something of an oddity compared to its fellow-terrestrial planets. Whereas they all orbit our Sun with a certain degree of eccentricity (from fair to extreme), Venus is the closest to orbiting in a circular pattern. And with an orbital velocity of 35.02 km/s (126,072 km/h; 78,337.5 mph), Venus takes 224.7 Earth days to complete a single orbit around the Sun.
Retrograde Motion:
Another oddity of Venus is the peculiar nature of its rotation. Whereas most objects in our Solar System have a rotation that is in the same direction as their orbit around the Sun, Venus’ rotation is retrograde to its orbit. In other words, if you could view the Solar System from above the Sun’s northern polar region, all of the planets would appear to be orbiting it in a counter-clockwise direction.
They would also appear to be rotating on their axis in the same counter-clockwise direction. But Venus would appear to be slowly rotating in a clockwise direction, taking about 243 days to complete a single rotation. This is not only the slowest rotation period of any planet, it also means that a sidereal day on Venus lasts longer than a Venusian year.
A popular theory states that this is due to two major impacts taking place between Venus and a series protoplanets in the distant past. Much like the impact that is believed to have created the Moon (between Earth and Theia), the first of these impact would have created a moon in orbit of Venus, while a second (10 million years later) would reverseed its rotation and caused the moon to de-orbit.
Artist’s concept of a collision between proto-Earth and Theia, believed to happened 4.5 billion years ago. Credit: NASA
Every planet in our Solar System has is shares of quirks, and Venus is no exception. She’s “Earth’s Sister”, and she’s prone to extreme temperatures that do not vary. And her orbit is the most stable of any planet, also with very little variation. You might say Venus is the extremely hot-tempered sibling of Earth, and very straight-laced to boot!
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
Venus is known as Earth’s Sister Planet. It’s roughly the same size and mass as Earth, it’s our closest planetary neighbor, and Venus and Earth grew up together.
When you grow up with something, and it’s always been there, you kind of take it for granted. As a species, we occasionally glance over at Venus and go “Huh. Look at Venus.” Mars, exotic exoplanets in distant solar systems, and the strange gas giants and their moons in our own Solar System attract much more of our attention.
If a distant civilization searched our Solar System for potentially habitable planets, using the same criteria we do, then Venus would be front page news for them. It’s on the edge of the habitable zone and it has an atmosphere. But we know better. Venus is a hellish world, hot enough to melt lead, with crushing atmospheric pressure and acid rain falling from the sky. Even so, Venus still holds secrets we need to reveal.
Chief among those secrets is, “Why did Venus develop so differently?
Conditions on Venus pose unique challenges. The history of Venus exploration is littered with melted Soviet Venera Landers. Orbital probes like Pioneer 12 and Magellan have had more success recently, but Venus’ dense atmosphere still limits their effectiveness. Advances in materials, and especially in electronic circuitry that can withstand Venus’ heat, have buoyed our hopes of exploring the surface of Venus in greater detail.
The group acknowledged several over-arching questions we have about Venus:
How can we understand the atmospheric formation, evolution, and climate history?
How can we determine the evolution of the surface and interior?
How can we understand the nature of interior-surface-atmosphere interactions over time, including whether liquid water was ever present?
Since the Vision 2050 Workshop is all about the next 50 years, Cutts and his team looked at the challenges posed by Venus’ unique conditions, and how they could answer questions in the near-term, mid-term, and long-term.
Near Term Exploration (Present to 2019)
Near-Term goals for the exploration of Venus include improved remote-sensing from orbital probes. This will tell us more about the gravity and topography of Venus. Improved radar imaging and infrared imaging will fill in more blanks. The team also promoted the idea of a sustained aerial platform, a deep probe, and a short duration lander. Multiple probes/dropsondes are also part of the plan.
Dropsondes are small devices that are released into the atmosphere to measure winds, temperature, and humidity. They’re used on Earth to understand the weather, and extreme phenomena like hurricanes, and can fulfill the same purpose at Venus.
Dropsondes are released into the atmosphere, and their descent is slowed by a small parachute. As they descend, they gather data on temperature, wind, and humidity. Image By Staff Sgt. Randy Redman of the US Air Force
In the near-term, missions whose final destination is not Venus can also answer questions. Fly-bys by craft such as Bepi-Colombo, Solar Probe Plus, and the Solar Orbiter missions can give us good information on their way to Mercury and the Sun respectively. These missions will launch in 2018.
Bepi-Colombo, a joint mission of the ESA and JAXA, will perform two fly-bys of Venus on its way to Mercury. Image: ESA/JAXA
The ESO’s Venus Express and Japan’s Akatsuki, (Venus Climate Orbiter), have studied Venus’ climate in detail, especially its chemistry and the interactions between the atmosphere and the surface. Venus Express ended in 2015, while Akatsuki is still there.
Mid-Term Exploration (2020-2024)
The mid-term goals are more ambitious. They include a long-term lander to study Venus’ geophysical properties, a short-duration tessera lander, and two balloons.
The tesserae lander would land in a type of terrain found on Venus known as tesserae. We think that at one time, Venus had liquid water on it. The fundamental evidence for this may lie in the tesserae regions, but the terrain is extremely rough. A short duration lander that could land and operate in the tesserae regions would help us answer Venus’ liquid water question.
Thanks to the continued development of heat-hardy electronics, a long-term duration lander (months or more) is becoming more feasible in the mid-term. Ideally, any long-term mobile lander would be able to travel tens to hundreds of kilometers, in order to acquire a regional sample of Venus’ surface. This is the only way to take geochemistry and mineralogy measurements at multiple sites.
On Mars the landers are solar-powered. Venus’ thick atmosphere makes that impossible. But the same dense atmosphere that prohibits solar power might offer another solution: a sail-powered rover. Old-fashioned sail power might hold the key to moving around on the surface of Venus. Because the atmosphere is so dense, only a small sail would be necessary.
A simple sail-powered rover may solve the problem of mobility on the Venusian surface. Image: NASA
Long-Term Exploration (2025 and Beyond)
The long-term goals from Cutts and his team are where things get really interesting. A long-lived surface rover is still on the list, or possibly a near-surface craft like a balloon. Also on there is a long-lived seismic network.
A seismic network would really start to reveal the secrets behind Venus’ geophysical life. Whereas a lander would give us estimates of seismic activity, they would be crude compared to what a network of seismic sensors would reveal about Venus’ inner workings. A more thorough understanding of quake mechanisms and locations would really get the theorists buzzing. But it’s the final thing on the list that would be the end-goal. A sample-return mission.
We’re getting good at in situ measurements on other worlds. But for Venus, and for all the other worlds we have visited or want to visit, a sample return is the holy grail. The Apollo missions brought back hundreds of kilograms of lunar samples. Other sample-return missions have been sent to Phobos, which failed, and to asteroids, with varying degrees of success.
Subjecting a sample to the kind of deep analysis that can only be done on labs here on Earth is the end-game. We can keep analyzing samples as we develop new technologies to examine them with. Science is iterative, after all.
An artist’s image of Hayabusa leaving Earth. Hayabusa was a Japanese sample return mission to the asteroid 25143 Itokawa. The mission was a partial success. A sample mission to Earth’s sister planet is the holy-grail for the exploration of Venus. Image credit: JAXA
The 2003 Planetary Science Decadal Survey identified the importance of a sample return mission to Venus’ atmosphere. A balloon would float aloft in the clouds, and an ascending rocket would launch a collected sample back to Earth. According to Cutts and his team, this kind of sample-return mission could act as a stepping stone to a surface sample mission.
A surface sample would likely be the pinnacle of achievement when it comes to understanding Venus. But like most of the proposed goals for Venus, we’ll have to wait awhile.
The Changing Future
Cutts and the team acknowledge that the technology to enable exploration of Venus is in flux. No more missions to Venus are planned before 2020. There’ve been proposals for things like sail powered landers, but we’re not there yet. We’re developing heat-resistant electronics, but so far they’re very simple. There’s a lot of work to do.
On the other hand, some things may happen sooner. It may turn out that we can learn about Venusian seismic activity from balloon-borne or orbital sensors. The team says that “Due to strong mechanical coupling between the atmosphere and ground, seismic waves are launched into the atmosphere, where they may be detected by infrasound on a balloon or infrared or ultraviolet signatures from orbit.” That’s thanks to Venus’ dense atmosphere. That means that the far-term goal of seismic sensing of the interior of Venus could be shifted to the near-term or mid-term.
Japan’s Akatsuki orbiter captured this image of a gravity wave in Venus’ upper cloud layer. Could orbiter sensors remove the need for a network of seismic sensors on the surface? Image credit: JAXA
As work on nanosatellites and cubesats continues, they may play a larger role at Venus, and shift the timelines. NASA wants to include these small satellites on every launch where there is a few kilograms of excess capacity. A group of these nanosatellites could form a network of seismic sensors much more easily and much sooner than an established network of surface sensors. A network of nanosatellites could also serve as a communications relay for other missions.
Venus doesn’t generate a lot of buzz these days. The discovery of Earth-like worlds in distant solar systems generates headline after headline. And the always popular search for life is centered on Mars, and the icy/sub-surface moons of our Solar System’s gas giants. But Venus is still a tantalizing target, and understanding Venus’ evolution will help us understand what we’re seeing in distant solar systems.
The planet Venus, as imaged by the Magellan 10 mission. The planet's inhospitable surface makes exploration extremely difficult. Credit: NASA/JPL
Venus is often described as being hell itself, because of its crushing pressure, acidic atmosphere, and extremely high temperatures. Dealing with any one of these is a significant challenge when it comes to exploring Venus. Dealing with all three is extremely daunting, as the Soviet Union discovered with their Venera landers.
Actually, dealing with the sulphuric rain is not too difficult, but the heat and the pressure on the surface of Venus are huge hurdles to exploring the planet. NASA has been working on the Venus problem, trying to develop electronics that can survive long enough to do useful science. And it looks like they’re making huge progress.
Scientists at the NASA Glenn Research Centre have demonstrated electronic circuitry that should help open up the surface of Venus to exploration.
The first color pictures taken of the surface of Venus by the Venera-13 space probe. The Venera 13 probe lasted only 127 minutes before succumbing to Venus’s extreme surface environment. Credit: NASA
“With further technology development, such electronics could drastically improve Venus lander designs and mission concepts, enabling the first long-duration missions to the surface of Venus,” said Phil Neudeck, lead electronics engineer for this work.
With our current technology, landers can only withstand surface conditions on Venus for a few hours. You can’t do much science in a few hours, especially when weighed against the mission cost. So increasing the survivability of a Venus lander is crucial.
With a temperature of 460 degrees Celsius (860 degrees Fahrenheit), Venus is almost twice as hot as most ovens. It’s hot enough to melt lead, in fact. Not only that, but the surface pressure on Venus is about 90 times greater than Earth’s, because the atmosphere is so dense.
To protect the electronics on previous Venus landers, they have been contained inside special vessels designed to withstand the pressure and temperature. But these vessels add a lot of mass to the mission, and make sending landers to Venus a very expensive proposition. So NASA’s work on robust electronics is super important when it comes to exploring Venus.
The team at the Glenn Research Centre has developed silicon carbide semiconductor integrated circuits (Si C IC) that are extremely robust. Two of the circuits were tested inside a special chamber designed to precisely reproduce the conditions on Venus. This chamber is called the Glenn Extreme Environments Rig (GEER.)
The GEER (Glenn Extreme Environments Rig) facility can recreate the conditions of any body in our Solar System. (No, not the Sun, obviously.) Image: NASA/Glenn Research Centre
GEER is a special chamber that can recreate the conditions on any body in our Solar System. It’s an 800 Litre (28 cubic foot) chamber that can simulate temperatures up to 500° C (932° F), and pressures from near-vacuum to over 90 times the surface pressure of Earth. GEER can also simulate exotic atmospheres with its precision gas-mixing capabilities. It can mix very specific quantities of gases down to parts per million accuracy. For these tests, that means the unit had to reproduce an accurate recipe of CO2, N2, SO2, HF, HCl, CO, OCS, H2S, and H2O, down to very tiny quantities. And the tests were a success.
“We demonstrated vastly longer electrical operation with chips directly exposed — no cooling and no protective chip packaging — to a high-fidelity physical and chemical reproduction of Venus’ surface atmosphere,” Neudeck said. “And both integrated circuits still worked after the end of the test.”
In fact, the two circuits not only functioned after the test was completed, but they withstood Venus-like conditions for 521 hours. That’s more than 100 times longer than previous demonstrations of electronics designed for Venus missions.
A before (top) and after (bottom) image of the electronics after being tested in Venus atmospheric conditions. Image: NASA
The circuits themselves were originally designed to operate in the extremely high temperatures inside aircraft engines. “This work not only enables the potential for new science in extended Venus surface and other planetary exploration, but it also has potentially significant impact for a range of Earth relevant applications, such as in aircraft engines to enable new capabilities, improve operations, and reduce emissions,” said Gary Hunter, principle investigator for Venus surface electronics development.”
The chips themselves were very simple. They weren’t prototypes of any specific electronics that would be equipped on a Venus lander. What these tests showed is that the new Silicon Carbide Integrated Circuits (Si C IC) can withstand the conditions on Venus.
A host of other challenges remains when it comes to the overall success of a Venus lander. All of the equipment that has to operate there, like sensors, drills, and atmospheric samplers, still has to survive the thermal expansion from exposure to extremely high temperature. Robust new designs will be required in many cases. But this successful test of electronics that can survive without bulky, heavy, protective enclosures is definitely a leap forward.
If you’re interested in what a Venus lander might look like, check out the Venus Sail Rover concept.
