A mass of swirling gas and cloud at Venus’ south pole. Credit: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA/Univ. Oxford.
Here’s the latest view of the mass of swirling gas and clouds at Venus’ south pole. The Venus Express’s Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) has been keeping an eye on this polar vortex since the spacecraft arrived and discovered this huge storm in 2006. During the mission, VIRTIS has seen the vortex constantly transform, morphing from a double vortex into a squashed shape and into the eye-like structure seen here.
This image was taken in April 2007 but was just released this week.
Venus has a very choppy and fast-moving atmosphere, even though wind speeds are much slower at the planet’s surface. At the cloud tops about 70 km above the surface, winds can reach 400 km/h. At this altitude, Venus’ atmosphere spins about 60 times faster than the planet itself. Compared to Earth, this is a dizzying speed: even Earth’s fastest winds move at most about 30% of our planet’s rotation speed.
These polar vortices form when heated air from equatorial latitudes rises and spirals towards the poles, carried by the fast winds. As the air converges on the pole and then sinks.
High velocity winds spin westwards around the planet, and take just four days to complete a rotation. This ‘super-rotation’, combined with the natural recycling of hot air in the atmosphere, would induce the formation of a vortex structure over each pole.
A video of the vortex, made from 10 images taken over a period of five hours, can be seen here. The vortex rotates with a period of around 44 hours.
Artist’s impression of the Venus Climate Orbiter (aka. “Akatsuki”) by Akihiro Ikeshita.
Image Credit: JAXA
Back in 2010, the Japanese Aerospace Exploration Agency (JAXA) launched the The Venus Climate Orbiter “Akatsuki” with the intention of learning more about the planet’s weather and surface conditions. Unfortunately, due to engine trouble, the probe failed to make it into the planet’s orbit.
Since that time, it has remained in a heliocentric orbit, some 134 million kilometers from Venus, conducting scientific studies on the solar wind. However, JAXA is going to make one more attempt to slip the probe into Venus’ orbit before its fuel runs out.
Since 2010, JAXA has been working to keep Akatsuki functioning so that they could give the spacecraft another try at entering Venus’ orbit.
After a thorough examination of all the possibilities for the failure, JAXA determined that the probe’s main engine burned out as it attempted to decelerate on approach to the planet. They claim this was likely due to a malfunctioning valve in the spacecraft’s fuel pressure system caused by salt deposits jamming the valve between the helium pressurization tank and the fuel tank. This resulted in high temperatures that damaged the engine’s combustion chamber throat and nozzle.
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
JAXA adjusted the spacecraft’s orbit so that it would establish a heliocentric orbit, with the hopes that it would be able to swing by Venus again in the future. Initially, the plan was to make another orbit insertion attempt by the end 2016 when the spacecraft’s orbit would bring it back to Venus. But because the spacecraft’s speed has slowed more than expected, JAXA determined if they slowly decelerated Akatsuki even more, Venus would “catch up with it” even sooner. A quicker return to Venus would also be advantageous in terms of the lifespan of the spacecraft and its equipment.
But this second chance will likely be the final chance, depending on how much damage there is to the engines and other systems. The reasons for making this final attempt are quite obvious. In addition to providing vital information on Venus’ meteorological phenomena and surface conditions, the successful orbital insertion of Akatsuki would also be the first time that Japan deployed a satellite around a planet other than Earth.
If all goes well, Akatsuki will enter orbit around Venus at a distance of roughly 300,000 to 400,000 km from the surface, using the probe’s 12 smaller engines since the main engine remains non-functional. The original mission called for the probe to establish an elliptical orbit that would place it 300 to 80,000 km away from Venus’ surface.
This wide variation in distance was intended to provide the chance to study the planet’s meteorological phenomena and its surface in detail, while still being able to observe atmospheric particles escaping into space.
Artist’s impression of Venus Express entering orbit in 2006. Image Credit: ESA – AOES Medialab
At a distance of 400,000 km, the image quality and opportunities to capture them are expected to be diminished. However, JAXA is still confident that it will be able to accomplish most of the mission’s scientific goals.
In its original form, these goals included obtaining meteorological information on Venus using four cameras that capture images in the ultraviolet and infrared wavelengths. These would be responsible for globally mapping clouds and peering beneath the veil of the planet’s thick atmosphere.
Lightning would be detected with a high-speed imager, and radio-science monitors would observe the vertical structure of the atmosphere. In so doing, JAXA hopes to confirm the existence of surface volcanoes and lighting, both of which were first detected by the ESA’s Venus Express spacecraft. One of the original aims of Akatsuki was to complement the Venus Express mission. But Venus Express has now completed its mission, running out of gas and plunging into the planet’s atmosphere.
But most of all, it is hoped that Akatsuki can provide observational data on the greatest mystery of Venus, which has to do with its surface storms.
Artists impression of lightning storms on Venus. Credit: ESA
Previous observations of the planet have shown that winds that can reach up to 100 m/s (360 km/h or ~225 mph) circle the planet every four to five Earth days. This means that Venus experiences winds that are up to 60 times faster than the speed at which the planet turns, a phenomena known as “Super-rotation”.
Here on Earth, the fastest winds are only capable of reaching between 10 and 20 percent of the planet’s rotation. As such, our current meteorological understanding does not account for these super-high speed winds, and it is hoped that more information on the atmosphere will provide some clues as to how this can happen.
Between the extremely thick clouds, sulfuric rain storms, lightning, and high-speed winds, Venus’ atmosphere is certainly very interesting! Add to the fact that the volcanic, pockmarked surface cannot be surveyed without the help of sophisticated radar or IR imaging, and you begin to understand why JAXA is eager to get their probe into orbit while they still can.
And be sure to check out this video, courtesy of JAXA, detailing the Venus Climate Orbiter mission:
Images from the Rosetta spacecraft show Philae drifting across the surface of its target comet during landing Nov. 12, 2014. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
It seems a lot of the space stories of this year involve spacecraft making journeys: bouncing across a comet, or making their way to Mars. Private companies also figure prominently, both in terms of successes and prominent failures.
These are Universe Today’s picks for the top space stories of the year. Disagree? Think we forgot something? Let us know in the comments.
10. End of Venus Express
Artist’s impression of Venus Express performing aerobreaking maneuvers in the planet’s atmosphere in June and July 2014. Credit: ESA–C. Carreau
This month saw the end of Venus Express’ eight-year mission at the planet, which happened after the spacecraft made a daring plunge into part of the atmosphere to learn more about its properties. The spacecraft survived the aerobraking maneuvers, but ran out of fuel after a few engine burns to raise it higher. Soon it will plunge into the atmosphere for good. But it was a productive mission overall, with discoveries ranging from a slowing rotation to mysterious “glories”.
9. Continued discoveries by Curiosity and Opportunity
1 Martian Year on Mars! Curiosity treks to Mount Sharp in this photo mosaic view captured on Sol 669, June 24, 2014. Navcam camera raw images stitched and colorized. Credit: NASA/JPL-Caltech/Marco Di Lorenzo/Ken Kremer – kenkremer.com
Methane? Organics? Water? Mars appears to have had these substances in abundance over its history. Continued work from the Curiosity rover — passing its second Earth year on Mars — found methane fluctuating in Gale Crater, and the first confirmed discovery of organics on the Martian surface. Opportunity is almost 11 years into its mission and battling memory problems, but the rover is still on the move (passing 41 kilometers) to an area that could be full of clay.
8. Siding Spring at Mars and the level of study of the comet by other missions at Mars
Comet Siding Spring near Mars in a composite image by the Hubble Space Telescope, capturing their positions between Oct. 18 8:06 a.m. EDT (12:06 p.m. UTC) and Oct. 19 11:17 p.m. EDT (Oct. 20, 3:17 a.m. UTC). Credit: NASA, ESA, PSI, JHU/APL, STScI/AURA
We had a rare opportunity to watch a comet make a grazing pass by Mars, not close enough to pose significant danger to spacecraft, but definitely close enough to affect its atmosphere! Siding Spring caught everyone’s attention throughout the year, and did not disappoint. The numerous spacecraft at the Red Planet caught glimpses, including from the surface and from orbit. It likely created a meteor shower and could alter the Martian atmosphere forever.
7. Kepler K2
Illustration of the Kepler spacecraft (NASA/Kepler mission/Wendy Stenzel)
The Kepler space telescope lost the second of its four pointing devices last year, requiring a major rethink for the veteran planet hunter. The solution was a new mission called K2 that uses the pressure of the Sun to maintain the spacecraft’s direction, although it has to flip every 83 days or so to a new location to avoid the star’s glare. It’s not as precise as before, but with the mission approved we now know for sure K2 can locate exoplanets. The first confirmed one is a super-Earth.
6. MAVEN at Mars
An artist’s conception of MAVEN orbiting Mars. Image Credit: NASA / Goddard Space Flight Center
Where did the Martian atmosphere go? Why was it so thick in the past, allowing water to flow on the surface, and so thin right now? The prevailing theory is that the Sun’s pressure on the Martian atmosphere pushed lighter isotopes (such as that of hydrogen) away from the planet, leaving heavier isotopes behind. NASA is now investigating this in more detail with MAVEN (Mars Atmosphere and Volatile Evolution), which arrived at the planet this fall.
5. India’s MOM
Artist’s impression of India’s Mars Orbiter Mission (MOM). Credit ISRO
India made history this year as only the third entity to successfully reach the Red Planet (after the United States and Europe). While updates from the Mars Orbiter Mission have been slow in recent weeks, we know for sure that it observed Siding Spring at Mars and it has been diligently taking pictures of the Red Planet, such as this one of the Solar System’s largest volcano and a huge canyon on Mars.
4. Accidents by Virgin and Orbital
NTSB investigators are seen making their initial inspection of debris from the Virgin Galactic SpaceShipTwo. The debris field stresses over a fiver mile range in the Mojave desert. (Credit: Getty Images)
In one sobering week in October, the dangers of space travel were again made clear after incidents affected Virgin Galactic and Orbital Sciences. Virgin lost a pilot and seriously injured another when something went seriously awry during a flight test. Investigators have so far determined that the re-entry system turned on prematurely, but more details are being determined. Orbital meanwhile suffered the catastrophic loss of one of its Antares rockets, perhaps due to Soviet-era-designed engines, but the company is looking at other ways to fulfill its NASA contractual obligations to send cargo to the International Space Station.
3. SpaceX rocket landing attempts
The Falcon 9 rocket with landing legs in SpaceX’s hangar at Cape Canaveral, Fl, preparing to launch Dragon to the space station this Sunday March 30. Credit: SpaceX
SpaceX is attempting a daunting technological feat, which is bringing back its rocket first stages for re-use. The company is hoping that this will cut down on the costs of launch in the long term, but this technological innovation will take some time. The Falcon 9 rocket stage that made it back to the ocean in July was deemed a success, although the force of the landing broke it apart. Next, SpaceX is trying to place its rocket on an ocean platform.
2. Orion flight
Orion Service Module fairing separation. Credit: NASA TV
NASA’s spacecraft for deep space exploration (Orion) successfully finished its first major uncrewed test this month, when it rode into orbit, made a high-speed re-entry and successfully splashed down in the ocean. But it’s going to be a while before Orion flies again, likely in 2017 or even 2018. NASA hopes to put a crew on this spacecraft type in the 2020s, potentially for trips to the Moon, an asteroid or (more distantly) Mars.
1. Rosetta
New Rosetta mission findings do not exclude comets as a source of water in and on the Earth’s crust but does indicate comets were a minor contribution. A four-image mosaic comprises images taken by Rosetta’s navigation camera on 7 December from a distance of 19.7 km from the centre of Comet 67P/Churyumov-Gerasimenko. (Credit: ESA/Rosetta/Navcam Imager)
It’s been an exciting year for the Rosetta mission. First it woke up from a lengthy hibernation, then it discovered that Comet 67P/Churyumov-Gerasimenko looks a bit like a rubber duckie, and then it got up close and released the Philae lander. The soft touchdown did not go as planned, to say the least, as the spacecraft bounced for two hours and then came to rest in a spot without a lot of sunlight. While Philae hibernates and controllers hope it wakes up again in a few months, however, science results are already showing intriguing things. For example, water delivered to Earth likely came mostly from other sources than comets.
Artist's impression of Venus Express entering orbit in 2006. Credit: ESA - AOES Medialab
Venus Express is mostly dead. The spacecraft spent more than eight years faithfully relaying information from the Morning Star/Evening Star planet, but it’s now out of fuel, out of control and within weeks of burning up in the atmosphere.
While we mourn the end of the productive mission, the European Space Agency spacecraft showed us a lot about the planet that we once considered a twin to Earth. Some of the surprises, as you can see below, including a possibly slowing-down rotation, and the realization that volcanoes may still be active on the hellish planet.
False color composite of a rainbow-like feature known as a ‘glory’, seen on Venus on 24 July 2011. The image is composed of three images at ultraviolet, visible, and near-infrared wavelengths from the Venus Monitoring Camera. The images were taken 10 seconds apart and, due to the motion of the spacecraft, do not overlap perfectly. The glory is 1200 km across, as seen from the spacecraft, 6000 km away. It’s the only glory ever seen on another planet. Credit: ESA/MPS/DLR/IDA.
Quick video summary: Venus Express found that the spacecraft’s rotation may have slowed down by 6.5 minutes between 1996 (when the Magellan spacecraft was in orbit) and 2012. The surprising information emerged when scientists discovered surface features weren’t in the expected areas, and couldn’t find any calculation errors between the data.
Animation of Venus’ southern polar vortex made from VIRTIS thermal infrared images; white is cooler clouds at higher altitudes. Credit: ESA/VIRTIS-VenusX/INAF-IASF/LESIA-Obs. de Paris (G. Piccioni, INAF-IASF)
Quick video summary: Volcanic flows may still be active on Venus’ surface, according to 2010 data from the mission. Scientists looked at surface areas that had not been “weathered” very much (indicating that they are relatively young) and detected at least nine spots where the heat in those zones is much higher than the areas around it.
A picture of Venus’ clouds. Despite the planet being extremely hot, Venus Express found a cold layer in the atmosphere at temperatures of about -175 degrees Celsius (-283 Fahrenheit) that is colder than anything on Earth. It’s so chilling that carbon dioxide may freeze and fall as snow or ice. Credit: ESA/MPS/DLR/IDAArtist’s impression of Venus with the solar wind flowing around the planet, which has little magnetic protection. Venus Express found that a lot of water has bled into space over the years from the planet, which happens when the sun’s ultraviolet radiation breaks oxygen and hydrogen molecules apart and pushes them into space. Credit: ESA – C. Carreau
“The available information provides evidence of the spacecraft losing attitude control,” stated Patrick Martin, ESA’s Venus Express mission manager, who added it was because the machine exhausted its fuel as controllers tried to raise it to a more stable altitude above Venus.
The demise of the mission, in a sense, began when controllers chose to bring Venus Express into the atmosphere this summer. The goal was not only to learn more about Venus, but also to get information on how future spacecraft could “surf” the atmosphere when, say, landing on the planet.
Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau
The orbit was reduced to about 130 km to 135 km (80.7 miles to 83.9 miles) above the planet at its lowest approach, which took place in earnest between June 18 and July 11. Controllers then did 15 small thruster burns, which raised the spacecraft’s minimum altitude to 460 km (286 miles).
But it wasn’t a stable orbit, with the spacecraft continuing to spiral into the planet as gravity pulled it down. ESA decided to again try raising the spacecraft’s altitude between Nov. 23 and Nov. 30, but lost consistent contact with the spacecraft Nov. 28. It appears Venus Express is out of gas, the agency said.
It’s hard to know exactly when the spacecraft will die, but it serves as a good example of how space recycling can end up making an interesting mission. The design and some of the instruments on Venus Express were based upon those used for other missions, particularly Mars Express and Rosetta. And the lessons of the spacecraft will certainly be used in future missions.
Tomorrow, we’ll run down some of the highlights of the mission.
After more than eight years orbiting a hellish planet, Venus Express is showing its age. The spacecraft made some risky maneuvers this summer, dipping down into the atmosphere as it nears the end of its mission. Now, the European Space Agency reports it has mostly lost contact with the probe. The reason could be lack of fuel.
The “anomaly” started Nov. 28 when the agency’s operations center lost touch with the spacecraft. Since then, ground stations at ESA and NASA have been trying to hail the probe. All they’ve received since then is a little bit of telemetry showing that the spacecraft has it solar panels pointing towards the Sun, and it’s slowly rotating.
Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau
“It is possible that the remaining fuel on board VEX was exhausted,” ESA wrote in a blog post, pointing out that in recent weeks it has been trying to raise the spacecraft’s altitude for more science observations. But with the spacecraft spinning, its high-gain antenna is likely out of contact with Earth and it’s hard to reach it.
“The operations team is currently attempting to downlink the table of critical events that is stored in protected memory on board, which may give details of the sequence of events which occurred over the past few days,” ESA added. “The root cause of the anomaly (fuel situation or otherwise) remains to be established.”
Artist's impression of Venus Express performing aerobreaking maneuvers in the planet's atmosphere in June and July 2014. Credit: ESA–C. Carreau
It’s been an interesting year for Venus Express. A few months ago, controllers deliberately dipped the spacecraft into the atmosphere of the planet — for science purposes, of course. The daring maneuver was approved because the spacecraft is near the end of its mission. It’s nearly out of fuel and will fall into Venus — sometime. Likely in 2015. No one knows exactly when, however.
Until Dec. 30, European Space Agency operators are going to boost the spacecraft’s orbit to try to get a little more productivity out of it. After that, all depends on what gas is left in the tank.
The push against the dense atmosphere revealed a few surprises. In a recent blog post, ESA said the atmosphere was changing more than expected. Between different altitudes, controllers sometimes saw a steady rise in pressure and sometimes multiple peaks. The spacecraft’s journeys took it as low as 129.2 kilometers (80 miles) above the surface, but mostly involving a month of “surfing” between 131 km and 135 km (81.4 miles and 83.9 miles).
Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau
“One possible explanation is that we detected atmospheric waves,” stated Håkan Svedhem, Venus Express project scientist.
“These features can be caused when high speed winds travel over mountain ranges. The waves then propagate upwards. However, such waves have never before been detected at such heights – twice the altitude of the cloud deck that blankets Venus.”
ESA observed that the atmospheric density increased 1,000 times between 165 km and 130 km (102.5 miles and 80.8 miles) and that it also changed when the spacecraft moved from day to night (specifically, it was four times greater on the sunlit side.) Measurements were also taken of high-energy particles and Venus’ magnetic fields, which are still being examined.
False colour composite of a ‘glory’ seen on Venus on 24 July 2011. The image is composed of three images at ultraviolet, visible, and near-infrared wavelengths from the Venus Monitoring Camera. The images were taken 10 seconds apart and, due to the motion of the spacecraft, do not overlap perfectly. The glory is 1200 km across, as seen from the spacecraft, 6000 km away. Credit: ESA/MPS/DLR/IDA.
But now, the end is indeed near for the spacecraft after eight years at Venus — four times longer than its primary mission. Although it is healthy and performing routine science operations, fuel is only standing at around 3 kilograms (6.6 pounds) and oxidizer at 5 kg (11 lbs). It’s possible not all of it is accessible due to propellant movement in the tanks, ESA said. The new maneuvers are expected to subtract 1.4 kg of fuel and 2 kg of oxidizer from these totals.
“Unfortunately, we do not know how much fuel remains in its tanks, but we are intending to continue the up-down process as long as possible, until the propellant runs out,” Svedhem added.
“We have yet to decide whether we shall simply continue until we lose control, allowing it to enter the atmosphere and burn up naturally, or whether we attempt a controlled descent until it breaks up.”
Does the atmosphere of Venus possess upper atmospheric phenomena similar to the Earth, such as aurora or nightglow?
Now, a recent announcement out of the American Astronomical Society’s 46th annual meeting of the Division of Planetary Science being held this week in Tucson, Arizona has shed new light on the dilemma.
The discovery was announced on Wednesday, November 12th at the 46th AAS meeting and was made as a collaborative effort by researchers from New Mexico State University at Las Cruces, the Stanford Research Institute (SRI) International, the University of Colorado at Boulder, the University of Koln and University of Munich, Germany, the European Space and Technology Center in the Netherlands and the Institut de Recherche en Astrophysique et Planétologie, in France.
For the study, researchers observed Venus from December 2010 to July 2012 using the Astrophysical Research Consortium (ARC)Echelle Spectrograph and the ARC 3.5 metre telescope located at Apache Point near Sunspot, New Mexico.
Timing was crucial, as the Sun was coming off of a profound deep minimum through 2009 and just beginning to become active with the start of solar cycle #24. Observers were looking for activity along the 5577.3 angstrom wavelength known as the “oxygen green line.” Activity had not been seen at this wavelength on the nighttime side of Venus since 2004.
The altitude drop in the Venusian atmosphere measured in the study. Credit : Credit: DPS press release/C. Gray/New Mexico State University.
“These are intriguing results, suggesting that it is possible to have aurora on non-magnetic planets,” said Candace Gray, Astronomer and NASA Earth and Space Science Fellow at Las Cruces and lead researcher in the study. “On Venus, this green line has been seen only intermittently.”
Earth is the oddball among the terrestrial planets in the inner solar system with its robust magnetic field. On Earth, aurorae occur when said field captures charged particles ejected from the Sun and funnels them in towards the poles. Events seen in the study tended to drop 140 to 120 kilometres in altitude in the Venusian atmosphere, highly suggestive of auroral activity seen in the ionosphere of Earth.
Researchers were fortunate during one of the recent runs at Apache Point that the Sun kicked off a coronal mass ejection that headed Venus’s way. During the July 2012 solar storm, the team detected one of the brightest green line emissions that had ever been detected by observers on Earth.
The 3.5 metre telescope at Apache Point, in this case, being used for lunar ranging experiments. Credit: M3long/Wikimedia Commons image.
This demonstrates that perhaps, a magnetic field is optional when it comes to auroral activity, at least in the case of the planet Venus. Located only 0.7 astronomical units (108.5 million kilometres) from the Sun, our tempestuous star actually wraps the planet with its very own magnetotail.
Researchers are also looking to compare their results with observations from the European Space Agency’s Venus Express orbiter which arrived at the planet on April 2006.
“Currently, we are using observations from VIRTIS on Venus Express to try and detect the green line,” Gray told Universe Today. “We had coordinated ground based observations with them this past February, and we detected the green line from the ground when they were observing the night side limb. Additionally, we are using the Electron Spectrometer and ASPERA-4 to observe how the electron energy and density changes in the atmosphere after coronal mass ejection impacts.”
This also raises the interesting possibility that NASA’s MAVEN spacecraft — which recently arrived in orbit around Mars — might just detect similar activity in the tenuous Martian atmosphere as well. Like Venus, the Red Planet also lacks a global magnetic field.
Could this glow be connected with spurious sightings of the “Ashen Light of Venus” that have cropped up over the centuries?
Of course, ashen light, also known as Earthshine on the dark limb of the Moon, is easily explained as sunlight reflected back from the Earth. Moonless Venus, however, should be ashen light free.
“The green line emission that we see is brightest on the limb (edge) of the planet,” Gray told Universe Today. “We’re sure that there is emission all along the nightside, but because of the optical depth, it appears much brighter on the limb of the planet. I think it would be too faint to detect with the naked eye.”
Nightglow has been a leading suspect for ashen light on the Venusian nightside, and a similar green line emission detection rivaling the 2012 event was made by Tom Slanger using the Keck I telescope 1999.
Other proposed suspects over the centuries for ashen light on Venus include lightning, volcanism, light pollution (!) from Venusian cities, or just plain old observer error.
Certainly, future observations are needed to cinch the solar activity connection.
“We will likely observe Venus again from Apache Point the next time Venus is visible to us in June 2015,” Gray told Universe Today. “We will continue looking at Venus Express observations until the craft dies in the atmosphere.”
Venus turns its night time back towards us during the 2012 transit of the Sun, as seen from NASA’s Solar Dynamics Observatory (Credit: NASA/SDO).
Venus can currently be seen crossing through the field of view of SOHO’s LASCO C3 camera. After spending most of 2014 in the dawn sky, Venus will emerge from behind the Sun low in the dusk to head towards greatest elongation in the evening sky on June 6th, 2015. And from there, Venus will once again slender towards a crescent, presenting its nightside towards Earth, and just perhaps, continuing to present a lingering mystery of modern astronomy.
It was a daring maneuver, but the plan to put Venus Express lower in the planet’s thick atmosphere has worked. For the past month, the European Space Agency steered the long-running spacecraft to altitudes as low as 81 miles (131 kilometers) for a couple of minutes at a time.
Now the spacecraft has been steered again to safer, higher orbits. And naturally, this was all done in the name of science. It not only showed scientists information about the atmosphere, but also gave them engineering data of how a spacecraft behaves when it touches a planetary atmosphere at high speed. That could be useful for future landing missions.
“We have collected valuable data on the Venusian atmosphere in a region difficult to characterise by other means,” stated Hakan Svedhem, Venus Express project scientist for the European Space Agency.
“The results show that the atmosphere seems to be more variable than previously thought for this altitude range, but further analysis will be needed in order to explain these variations properly.”
The dips into hell were hard on the spacecraft. At times, its temperatures rose by more than 212 degrees Fahrenheit (100 degrees Celsius). That said, initial surveys of the spacecraft show all is well, although more analysis will be needed. Also, its orbit was reduced by more than an hour because its speed was slowed down by so much.
While the spacecraft performed 15 thruster burns to raise up above the atmosphere, the reprieve will be temporary. There is little fuel left in the spacecraft, which has been been at the planet since 2006. Now its new lowest point in the orbit is 460 km (286 miles), but over the next few months it will fall again due to the force of gravity. Mission planners expect the spacecraft will survive until about December, when it falls into the atmosphere for good.
“Aerobraking can be used to reduce the speed of a spacecraft approaching a planet or moon with an atmosphere, allowing it to be captured into orbit, and to move from an elliptical orbit to a more circular one,” the agency wrote.
“Less fuel has to be carried, yielding benefits all round. The technique will be used on future missions and the Venus Express experiments will help guide their design.”
Artist’s conception of Venus Express doing an aerobraking maneuver in the atmosphere in 2014. Credit: ESA–C. Carreau
Here’s another marvel of technology: there are people on Earth who are formulating solar weather forecasts … for Venus. While that sounds counterintuitive — isn’t the sun far away from that planet? — it actually does have a big effect on the planet’s atmosphere. And with Venus Express taking the plunge into the planet’s atmosphere, it’s important to know how the sun is behaving to predict its effect.
As the spacecraft skims the top of the planet’s atmosphere, it’s possible that if an extreme weather event occurs, this could change the orbit from what would be predicted.
“The space weather reports will … allow us to better understand anomalous behaviour that we may subsequently observe on the spacecraft,” stated Adam Williams, Venus Express’ deputy spacecraft operations manager.
“And in extreme cases, we would be more ready to react to a serious situation. For example, if our startrackers were to be overloaded by radiation.”
We’re used to regular solar weather reports on Earth, but getting them ready for Venus — a first — is a bit more difficult. The European Space Agency is using observatories such as the Solar Dynamics Observatory, the Solar and Heliospheric Observatory and the Proba-2 spacecraft, just like it does for Earth forecasts.
On August 31, 2012 a long filament of solar material that had been hovering in the sun’s atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. The coronal mass ejection, or CME, traveled at over 900 miles per second.
Venus presents an extra challenge, however, because it’s 59 degrees ahead of Earth in its orbit (as things stand right now) and there are no spacecraft in between the Sun and Venus to see how conditions change as particles head toward the planet. The updates are being issued through ESA’s Space Weather Coordination Centre in Belgium.
By the way, we’re also lucky enough to get weather forecasts for another planet — Mars! Malin Space Science Systems provides weekly weather reports from the Red Planet through the Mars Color Imager (MARCI) on the Mars Reconnaissance Orbiter. Here’s part of its report from between May 26 and June 1. (Be sure to click through the link to watch a recent video of Mars rotating).
Dust storm frequency increased this week in the southern tropical latitudes west and north of Argyre with local storms of varying size and duration observed in Aonia, Solis, Syria, and Tharsis. Dust haze resulting from these storms was present in the western portions of Valles Marineris. Other storm activity occurred in Noachis, as well as in the northern hemisphere off the residual north polar cap. Diffuse water ice clouds were present over Utopia and equatorial latitudes. At southern mid-to-high latitudes, seasonal frost was present up to approximately 55 degrees south latitude. Other than occasional diffuse water ice clouds over Meridiani, skies were relatively storm free over the Opportunity rover site at Endeavor Crater and the Curiosity rover site at Gale Crater.
